/ Motoring

Warning lights on? Your car will fail its MOT test

New tougher MOT rules will require your car dashboard’s warning lights to be working. If they don’t, your car will fail its MOT test. Is this a much needed safety improvement or a route to more rip offs?

The MOT test now includes a ‘Malfunction Indicator Lamp’ check. This requires the examiner to visually check that warning lights for electronic stability control, safety restraint systems, anti-lock braking systems and tyre pressure monitoring systems are not permanently illuminated.

The requirement came into effect on 1 January to comply with a revised European testing directive. It will be highlighted as an ‘advisory’ item only until 31 March, but from 1 April onwards, vehicles will fail an MOT if these lights are illuminated.

It’s just a visual check – so doesn’t require any diagnostic equipment to evaluate the actual cause of the light being on, but you can bet your bottom dollar the garage will charge you to investigate why a light is on (it will scan the system for a fault code, pointing to the cause).

The risk of rogue warning lights

When I recently asked my Renault dealer to investigate a warning light, the first thing they said was that there would be a £45 charge for a diagnostic check, then additional rectification costs depending on what that revealed.

My ‘fault’ was a service warning to check the handbrake (not covered by the new MOT rules as far as I can tell) which came on after the battery was disconnected.

As an ex-mechanic, I checked the physical components of the handbrake and there wasn’t an actual handbrake fault. In my view, it was simply a rogue indication because of the loss of power to the system. But to find that out for sure, I have to stump up £45, without even thinking of any consequential costs.

Don’t get me wrong, I completely agree that these lights are important – and if functioning correctly, they can let you know of a genuine safety risk.

So it seems sensible to make these an advisory notice. But, to me, the idea that they constitute an automatic MOT failure (without a proper investigation) leaves motorists open to being charged extra, perhaps simply because modern electronic systems are still too quirky and can display rogue signals from time to time. Would your car pass these new MOT rules?

Response Diagnostics says:
17 October 2012

Absolutely Motor Tech,
I find it beyond belief that the general public think we should give away our living to do them (a complete stranger) a favour, after all just last week I went into a shoe shop to get some kids shoes and the shop assistant said “I can see you haven’t got a lot of money at the moment, have those shoes for free”. I then went to the Supermarket and they let me have a trollyfull of shopping for nothing, like hell they did!
Customers also say “can you just quickly find out what it is for me and I’ll come back to have it repaired later” i.e I’ll get my brother-in-law to fix it with cheap ebay parts, as if the diagnosis is the easy bit. I usually give them one of my favourite sayings “mechanical faults take minutes to diagnose and hours to repair, electrical faults take hours to diagnose and minutes to repair”. So I point out to them that the diagnosis is the hard bit and I will charge for it, their alternative is to go to the “cheap” garage who by the time honoured method of “parts darts” will spend twice as much of their money replacing unnecessary parts than my diagnostic bill would be and still their car is broken.
I find it frustrating that many new customers immediately approach me with an air of distrust, I much prefer customers where I have been recommended to them by friends, at least there is (usually) an element of trust then.
Steve, I agree about theft being an issue but this is not the topic under discussion here. The problem here is that owners STILL believe that the warning lights are “bogus” or “rogue” they are not, they are only a warning that the system has developed a fault, this fault is REAL. Just because the driver is not astute enough to detect the problem or the current driving conditions do not cause any symptoms to be showing does not change this fact. The overhaul to the MOT does not cover all warning lights but specific safety related items.

Steve says:
17 October 2012


“owners STILL believe that the warning lights are “bogus” or “rogue” they are not, they are only a warning that the system has developed a fault”

Here’s an example then: Whilst I usually buy the diagnostic equipment together with the vehicle (like VAG-COM when I buy a VW), I also take care of some small companie’s vehicle fleets.

Got six 2010-12 Sprinters. Almost ALL of them have the EML light come on intermittantly (as well as the brake/ABS warning lights in rainy weather). As they are under warranty, it doesn’t cost anything to take them to the dealer. In actually ALL cases Stardiagnostics returned NO fault.
So I tell drivers to treat it like e Windows computer: Re-start and the fault is gone. If not we need to have a look.

Conclusion: You need to know how to interpret EML lights, watch their behaviour, find out when they are real or when they just play up.

As for the qualifications: My experience has been that formal qualifications don’t say a lot. Often it is the old technician that takes a common sense approach to things whereas the younger ones are geeks who like to play with the computer rather then doing their “homework”.
It’s a matter of experience, not of what’s on paper.
…which does not mean that I resent good education! But in the end a person’t attitude can spoil even that.

What I tell people about the EML light: If it stays on or returns, then there’s a fault. Don’t panic, watch it! I’m not going on about insurance and legal matters, I’m not legalistic, prefer common sense. So I tell people that the EML light can be an early warning of a potential upcoming breakdown.or damage (catalys e.g.). I tell them it’s a helper, not as a yellow ££ sign with legal implications 🙂

As for taking the topic a bit beyond its origin: I have a feeling that people often get done for the wrong things first- like EML lights on MOT whereas the more important issues are not dealt with. Which is why I can understand the irritation of some people about this. The owner of a vehicle will always see it all in context, not just this one issue. But it all adds up in ones pocket.
That should be back on topic then…

Hi, I’ve just had my car fail its mot due to the airbag light coming on during the mot. Its never come on before. Cost to fix is a little under£500 with mot and diagnostics charge. Everyone i work with believes I’m being ripped of as I’m female, the car is well maintained and only ever been serviced at approved dealer any advice?

This comment was removed at the request of the user

Tanya, I’d take it to another garage to get a quote. You might find one locally in Which? Trusted Traders.

Hi Tanya – Sometimes warning lights can be activated when there is no fault. For some models of car there are instructions or even YouTube videos online showing how to reset the warning light, but if it happens again you will need to have it fixed.

Motor Tech says:
17 October 2012


Let’s try to keep to the point here.

Most garages have ZERO or very little training when it comes to diagnostics and fault finding – FACT. They are guessing and spending customers cash in the process.

The ATA Master Technician assesses a technicians capability to do the job FACT.

Price is definitely a factor. A cheap garage will not have a business which can sustain investment in equipment, training, insurance etc.

Motor vehicle technology is one of the fastest moving areas of technical innovation and development. If the garage doesn’t have the latest equipment and training on the systems, they will not be able to effectively diagnose problems.

The customer should ask to see the garages training plan and qualifications. Get details of when, where and what they were last trained on. It will be obvious if the garage your in has the capability to rectify your fault, or is just going to guess. It will become apparent to all that ‘cheap’ garages can not and do not invest in training or proper equipment.


Response Diagnostics says:
17 October 2012

As I mentioned earlier on in the thread the engine management light is a slightly special case in that this can be brought on when the engine control system believes it may be causing a pollution infringement, sometimes the manufacturers set the limits “too close to the wire” and normal wear and tear can bring the system across the threshold for bringing the light on (EOBD rules). With ALL the others ABS, ESP, DSC,EPS etc. the warning light signifies a very real problem not a bogus one. So now because of that whenever a warning light comes on it is perceived to be bogus, no checking is done it is just ignored.
An ignition off cycle clears the warning light condition for many fault codes and allows the driver to try again, but now if the warning light comes back on it is not perceived as something to get looked at but just another part of the normal operation of their vehicle.
As far as I can find out the engine MIL is not actually included in the test as it was felt that engine problems would be detected by the emissions test anyway.
What seems to keep being missed is it is not the warning light that is the problem but the safety implications of the fault it is trying to warn the driver of. It is not all warning lights (low washer level etc. that will cause an MOT fail but only SAFETY related warning lights.
Unfortunately many garages are ill equipped to deal with electronic problems. I have been earning my living continuously in electronic design and fault finding since 1977 and some of the more arcane problems can keep me awake at night. I sometimes feel I am running a one man crusade to educate the public that they need someone like myself when the warning lamp comes on but motorists have always taken their car to the garage for everything (except perhaps bodywork where they know to go to a bodyshop) and it will take a long time to change this perception.
BTW I have no ATA qualification, my formal qualifications are in topics such as “Industrial control and servomechanisms” the rest is self taught, I often wonder if some motor industry official wanted to test me whether he would understand many of the tests I do, or why I do them. Having done fault finding for many years I have evolved a method that systematically gets me to the fault in the shortest time, I do not poke about hoping to hit the problem in a “shot in the dark manner”. Car electronics are mostly control systems similar to those used in industry for many years, its that now they are just catching up.

Hi I am thinking of buying a Citroen relay van it runs and drives ok but the engine light is on. The current owner has had ecr valve replaced, fault codes canceled but light is still on. He says Citroen can reset it. Is this true
P. s. he is taking it for mot on tues before I buy it do you think the emissions test will show up any major problems or just fail because this light is on?

Martian says:
29 December 2012

My Fiat Sedici (AKA Suzuki SX4) has an oil warning light that flashes for 1 minute after starting. It is to do with oil degradation and designed to tell you the car is due an oil service. On top of the service the dealer and independent were charging me an extra £48 to turn it off on top of the oil service. Last garage couldn’t get the software to do it so I said leave it.

I bought a £10 lead from ebay and downloaded the software for free of the internet to do it my self. Fed up with these useless lights that do nothing but cost us money. I am convinced it does nothing other than being a timed item as surely it would be able to turn itself off when clean oil was put in. I have even turned it off and it stayed off without changing the oil just to test.

In addition a flashing oil light usually spells big trouble and to stop engine immediately, I feel this has been put in place deliberately to scare the owner into taking it to the dealer.

Hi having read your comments Re. Oil light flashing for 1min my car doing same yes engine oil /filter changed the question is where the hell is the diagnostic socket located , on my machine it states it’s by the right hand side of the steering wheel under dash three mechs have all looked for it all panels removed can see all wiring but no socket !!! Please help before we go back to being apprentice mechs LOL. Many Thanks. ROB

bartelbe says:
21 February 2013

The problem is the ripoff prices to fix anything electrical or involving systems like the ABS. If the parts were sold at a reasonable price, then fine, but they are not. If the ABS went on my car, then the price of replacing the main ABS computer would greater than the value of the car! Even wheel sensors are often absurdly overpriced, after all they are just cheap as chips hall sensors. The prices need to come down, at the moment it is simply a way for manufacturers to fleece motorists.

Steve says:
21 February 2013

…and some dealerships apparently have now started to disconnect the diagnostics cable between connector and ECU- which does not necessarily trigger the EML light. But it prevents you from doing your own diagnostics. Have seen it a few times now that this happened after a vehicle went to the main dealer for warranty repairs.

Oh and airbag controllers need to be replaced after they got activated. They cannot be re-set- even if they just get activated by going through a dirt road without actually triggering the airbag due to low speed.

Response Diagnostics says:
22 February 2013

@bartelbe. Yes the prices manufacturers charge for spares is outrageous, but they know that certain parts have to be bought from them so they can charge what they like (I recently bought an ABS controller for a Ford Fusion, cost to me was about £450 and my marvellous trade discount was 4.5%. Would a supermarket sel a loaf for a margin that small? Of course not). Some parts of course are available aftermarket but in so many cases they are Far Eastern and junk. I often advise customers to stay away from them.
@Steve. Have never heard of the dealer disconnecting the diagnostic comms but if the car came to me I would just treat that as a fault, fix that and then find the real fault.
Not all airbag controllers are “one shot wonders” Ford usually allows three resets and some have no limit.
What I am talking about here is resetting of crash data not general fault code resetting which never has a limit (not on any SRS controller I have come across anyway). So if the unit will not reset it has to have “crash data” stored which means some part of the system has been deployed, usually this is a seatbelt pre-tensioner, which people do not always spot and can often occur when the impact is not severe enough to set off the main airbags.

Bob James says:
5 March 2013

There are many comments here that are very wide of the mark, I work in this industry and can assure you in most cases the warning lamps do indicate genuine faults.
It costs us thousands of pounds for genuine diagnostics equipment and its proper use takes time all of which is not unreasonably charged for, we do not make the cars or the rules, we do intend to make a living though.
It amazes us the amount of folk driving around with defective SRS systems and the warning light illuminated, their familys accident survival is put at risk because of a reluctance to have their cars in a decent order.
We obviously need lights and rules for those stupid enough to think a defective 100mph+ projectile needs no proper maintainence.

Steve says:
5 March 2013


1000s of pounds for diagnostics equipment- you don’t seem to realise that this is part of the problem. You should not need to have to invest so much in it. Systems should be simpler with clear messages OR diagnostic equipment should be provided for free byt manufacturers so that anyone can do it and have full control over potential repairs and costs.

The fact that warning lights can come on for stupid, non-safety related, far fetched resons has also been pointed out. The rules and systems don’t differenciate though.

But as you (like me) “work in the industry”, scare-and-provide is something that you are surely aware of too. It’s being used everywhere. And yes, t works. People fall for it…

Some of us take the responsibility of running a car seriously, Bob. I am appalled at the thought of any driver ignoring or disconnecting a warning light, not knowing if their car has a fault or a faulty warning system.

In many cases a warning light does come on due to a malfunction rather than a genuine fault. Properly designed and build electronic systems are incredibly reliable, and if the manufacturer was responsible for rectifying faults (at their cost) for at least ten years then they would not inflict second rate products on the motorist. Unfortunately, it is difficult to make some types of sensor as reliable, so the best the manufacturer can do is to make them easy to replace.

Steve is right about simple, clear messages providing useful information about faults, and I have made the same point earlier or in another Conversation. The manufacturers need to sort this out.

weeto45 says:
20 March 2014

hi we managed with out all this on board ecus years ago its one big con

Bob James says:
5 March 2013

@ Steve
What we should and should not have to invest in is our choice, they do not give vehicle lifts etc away either, we have to buy those too.
As you work in this industry you will be aware there is a vast difference between information made available under OBDII, EOBD directives and that which is manufacturer specific, much of this man.spec. information goes well beyond that available from a basic cheap EOBD scanner and depending on the manufacturers diagnostics system does a very good job of diagnosing faults.
These systems cost us money as they do to the ever reducing number of main dealers, we have to recover these costs if we are to remain in business.
We are busy, mainly because we do know our work and perform well at vehicle diagnostics work.
One other point, fault codes are not set willy nilly, there are protocols within the ecu’s requiring faults to occur on one or more occaisons before becoming set permanent.
What many owners are unaware of is the equipment we and others use can give far more information on the vehicles condition and service history, it is not that unusual to find cars showing 40-70.000 miles since last service together with very low oil levels, we now record this information on invoices in case of future problems.
If folk think car repairs are expensive now just look at the systems fitted to new cars, auto parking etc etc, its not scare mongering its technical evolution, folk want all the toys, the costs inevitably escalate.

Steve says:
5 March 2013

Well Bob,

You describe the current situation. But it’s no technical necessity that you need expensive diagnosctic equipment. It’s caused by manufacturer’s design choices.
They could either incorporate clear diagnostics in the ECU so one could extract it without equipment OR provide such software at low cost or for free as this is a by-product of developing engine controllers anyway.

Apart from this we should clearly differenciate between basic safety functions and non-vital faults that can just cost the owner money if e.g. the cambelt doesn’t get changed in time.

Want one more example on where we are with our “progress”? Electronic fuses. Sprinter showed yellow faulty bulb light on dash. Only had 8V on a rear light, so it was a bit dim. Suspected high resistance somewhere. But wiring was all ok. In the end it was the Sam Unit (£200+!) that got replaced (under warranty). Without “progress” this would have been a traceable wiring fault or would not have occurred at all.

The bottom line within all this progress is that manufacturers are trying to limit the end-user’s authority over his own property- to make a profit.
And law makers are supporting this with rules like these.

Big Mac says:
19 September 2014

Quite right, there is no necessity for the diagnostics to be so complicated and obscur, Europe has insisted that all cars past 2002 are OBD2 compliant, why don’t they insist that any OBD2 scanner can read any car, any fault? Why don’t they insist that the onboard computers stop sending up obscur warnings, and further insist that they tell us what the fault is, we already know that the computer is aware of what the fault is, as we have to use OBD scanners to retrieve said data, because manufactures choose to bury that data within the cars computer memory banks. Manufacturers should be forced to refrain from burying this data, and make it all readable from the car dash, replacing the vague messages we currently get (ABS FAULT) with a message which tells us offside rear abs sensor fault. It is a con, and I have news for Europe and manufactures, Europe is suffering.

Big Mac says:
19 September 2014

And fiurthermore, I have no problem paying for a mechanic to fix my car, I have a problem paying for him just to plug in a scanner to tell him what my car already knows, I have a problem when he charges me 3hrs labour for what actually took him 5 mins. Mechanics have historically inflated their bills, it’s disgusting that the Government are furthermore enabling them to fleece the customer. As a carpenter, I have never overpriced to fix things, infact on the contrary I have done jobs on the cheap. My money is made on Loyalty and referals, not by being a Charlatan. In life we all get what is due us, if we rip people off, we can eventually expect life to turn the tables on us when we are in need.

Martin R says:
5 February 2015

Similar situation in Volvo S40 Phase 1’s. The CEM controls all the interior and exterior lighting. High beam fails before the MOT. Volvo want a small sum of GBP450 for a new CEM.

When I opened the CEM the problem was found to be a small relay where the silvered contacts had burned up. Again, a case of manufacturers introducing parts they know will fail after a period of time to generate more income. The relay current rating was 10 amps.

The relay cost was GBP 1.45… I rest my case

Bob James says:
5 March 2013


We are lucky in having mostly responsible owners with your viewpoint, in fact these days we tend to invite the more irresponsible owners to take their vehicles elsewhere.
On the vast majority of modern vehicles the disconnecting of warning lights (leds) is a myth, it is just not possible without a degree of electronics knowledge and a good deal of work to gain access to said lights, most are built within the dash module.
In our experience, with a couple of outstanding exemptions, most manufacturers sytems are reasonably reliable.
These systems live in a harsh enviornment, I doubt many give a second thought when charging through deep water etc, even the best built systems man can devize fail, F1, NASA spacecraft, the new Boeing aircraft, nothing man made is infallible, people have to accept maintainence and repair as part of modern life, they can of course always invest in the required kit and do it themselves, there is no EU directive as to where the repairs take place.

Bob – It’s a relief to hear that most manufacturers’ warning light systems are reasonably reliable, but that’s not good enough for me. I appreciate that there are problems such as vibration, salt spray and voltage spikes but good design and use of high quality components can take care of these problems. I can accept that mechanical parts moving at high speed can fail but electrical problems are far too common in cars. I have had quite a lot of experience with electronics, including industrial/laboratory grade products and I am simply not impressed by car manufacturers, though I have not personally had any problems. As I say, we should demand that manufacturers foot the bill for failures in warning light systems and it will not be long before these problems are a thing of the past. I don’t know if you are old enough to remember the rot-boxes of the sixties, that would rust through in three years. That is history.

It does worry me that people are ‘taking their vehicles elsewhere’ because we have to share the roads with them. However, if they don’t have to pay to have faults in warning light systems to be corrected then the roads could be a safer place, with ‘only’ human failings to contended with. 🙁

@steve – design choices, quite agree, lets look at it from the manufacturer and consider the ink jet printer as an example.

Printer dirt cheap, ink bloody expensive.

Car costs one third of current price, mandatory servicing costs almost as much as the vehicle.

How long until this occurs? Throwaway cars will soon come about!

Steve says:
6 March 2013

…thow away cars? Not sure if we need or want them. Should be consumer’s decision….

On the safety issue: It still amazes me how much talk there is about safety on UK roads. There’s an annual MOT in the UK, 70mph max speed, a limited network of motorways. It’s 2 years in Germany, no general speed limit and you can do well over 2000km/day on motorways.
MOT itself is not much different from the UK and yet unsafe vehicles are not an issue.

Can anyone explain this?

I’m not an MOT tester but I have a policy of not threatening anyobody with “the law” or “safety” or “consequences” (insurance, MOT) if there’s a yellow light on.
I *only* explain what might have caused it and let people decide whether they want their ABS working or not.
And self-responsibility works with 99% of all people. 1% may want to fix it themselves.
None of them is a threat to road safety. Most accidents are caused by drivers (who may thing that with ABS they can just fly…)

Don’t want to go back to rust-boxes but back to some more common sense is really needed esp. with the law makers 🙂 It’s us who need to demand this.

Response Diagnostics says:
6 March 2013

What we have here is a polarisation:-
Those in the motor trade trying again and again to point out that the warning lights are brought on for a genuine reason and that reason is a safety related problem (I am ignoring low washer fluid level warning lights etc. as they are not in the MOT and therefore not a problem) and,
Those who are regular motorists who still after all this discussion believe all warning lights are a fiction designed to make them spend money on their cars unnecessarily.
It always worries me that the motorist coming the other way is going to be one of those who feels the ABS light that is on on his dash is nothing but a nuisance and chooses that exact moment to demonstrate to the world the benefits of ABS by sliding across the road into me because his isn’t working.
I think the reason a bi-annual MOT works in Germany is because they still care for their cars and appreciate them. As a result they do not need to be forced into looking after their cars. They still have them serviced and if anything goes wrong they voluntarily take it for repair.
In the UK with money being tight motorists have started missing regular services, but as I have mentioned before they do nothing to look after their cars themselves. So the poor thing rumbles on until it breaks, then they moan that it is “unreliable” and “should never have let them down”. With DIY maintenance beyond most motorists now it is important that a trained eye looks over the car occasionally. We now have a culture with cars like our domestic goods, buy it, run it until it breaks, buy another. This is ok for a TV or a dishwasher but a terrible idea for a piece of machinery that is so safety critical as a car.
There are some well documented design flaws that escape into the market place. The brake pressure sensor fault on Teves Mk60 ABS springs to mind (widely fitted to VW, Honda, Ford etc.) but on the whole cars are very reliable, it is just a question of scale. Electronically cars are probably fifty times more complex than they were twenty years ago, multiply that by the huge number of vehicles there are on the roads and you will get problems, and of course no one is discussing the millions of cars out there with no faults on them at the moment.
I know Wavechange thinks cars should be built to MilSpec but it’s never going to happen. Manufacturers know gadgets sell cars and the first buyer will almost certainly sell the car as soon as the warranty has expired. It’s the poor second user who gets saddled with the problems that the dealer has kept at bay for the first three years of the cars life.
I’m sure many do not appreciate how complex much of the electronics is in a current car, there are probably more parts in an ABS controller than in the car’s engine and gearbox combined
I personally would like cars that are less complex and better engineered but I doubt if anybody would buy them off the forecourt.
I do tell my customers if cars were properly made I wouldn’t have a business. But I didn’t design, build or sell them their car, I am only trying to repair it. As this is how I make my living then yes, I will charge them.

I am not expecting car electronics to be built to military specification. Industrial process control systems are extremely reliable, and have to be because having a failure that ruins a large batch of material would be too expensive to contemplate. Hi-Fi separates are familiar examples of good quality domestic electronics, whereas almost everything else in the home is of relatively poor quality. All my Hi-Fi gear, dating from the mid-80s, still works fine. Digital electronics is potentially less reliable than analogue devices but can – if properly designed – cope effectively with problems. Vehicle designers need to focus on important issues, and if manufacturers are forced to take responsibility for paying for repairs to warning light systems they will find a way of making them reliable. If you have only experienced what the motor industry has to offer I can understand why you think my ideas are not very practical.

I do share your desire for cars that are less complex and better engineered.

Martin R says:
5 February 2015

Wavechange – Make sure the de-coupling capacitors and filter/smoothing capacitors are replaced in your Hi-Fi kit from the 80’s. They will go leaky and horrible things can happen…

In years to come it will be mainly dry joints and capacitor failures that will cause cars electronic systems to fail.

Bob James says:
6 March 2013

A very balanced piece Response Diagnostics, I would go further, in general many folk in this country have become quite lazy when looking after their vehicles, we regularly have vehicles presented for MOT checks that can be fairly described as mobile skips, the accumulation of rubbish inside the car can be quite disgusting.
It is not at all unusual for people to drive around with various lights not working, we all see such cars on the road, hence dash bulb failure warning units and smart fuseboxes, door not closed alarms for those unaware of an open door, seat belt warning buzzers and so on, devices aimed at all those who can be bothered to check nothing for themselves.
Incidentally no water in or a non working washer unit is a MOT failure.

Today, a vehicle presented for service, owner admits it was some while since the last service, engine oil down nearly 1 ltr (it only holds 3) and the oil closely resembling bitumen, air filter choked with oil and general filth, pollen filter much the same minus the oil, 3 brakes with siezed sliders, 2 tyre pressures down by more than 4psi, headlight bulb failure, etc etc.
The car still had what was left of the original plugs fitted and now has nearly 80.000 miles recorded
last recording in the service book of work caried out was at 38,000
This is not that unusual and is no wonder the MOT failure rate here is so high, including 3 year old cars too.
Those in charge of road safety are basically responding to the situation being presented, how many road fatalities do we need before even more stringent checks on driving and maintainence become the norm.
People need only properly check the statistics not take too much notice of such ill informed writing as provoked this discussion.
It is hard to imagine how half decent “Cars Researcher” ends up with a Renault and is then surprised it has electrical faults, we see a lot of faulty Renaults but we do not own one!
BTW if you own a modern common rail diesel engined vehicle do not be surprised when the repair bills cause an economic write off for that either, being caring folk we do keep tissues handy for those of our customers so afflicted.

Response Diagnostics says:
7 March 2013

@Wavechange, No I have not only worked in the motor trade. My previous careers have involved electronics design and manufacture, CNC machine tool design and manufacture and semiconductor chip manufacture. Many of the machines I have been responsible for are one-offs or low volume machines. If something gave repeated problems we re-engineered it so it didn’t. Cars are a consumer product, manufacturers would be commiting financial suicide to make something that lasted forever. They know that cup holders, penclips and seat fabric designs sell cars, not brick outhouse engineering. The fact that the user has a right to expect the wheels not to fall off seems to have been forgotten in many cases.
It’s just that I am a realist and understand that they will make something they can punt out the door at a profit, not produce a forever car that will harm their bottom line.
The part of all this that galls me is that they have no concept of how their product will be maintained afterwards, with the result that many incidental parts have to be removed to get to the one item I wish to test/repair/replace.
@Bob J, Thanks for the complement, most will probably think of it as a rant!
I agree with the state of cars when presented, I have a clause in my Ts & Cs that states that cars presented in this condition will be cleaned prior to work commencing and I will charge full labour for doing so. Many cars have fuseboxes and electronics above the accelerator pedal, when a car comes in with 2 inches of fag ash on the floor there is no way I am going to put my hair in it!
People buy CR diesels to save money. I recently had a Civic iCTDi come in from a local fastfit type garage as a non-runner. Diagnosed failed injector on number 1. When attempting to remove it it would not move. Very poor access as there is little space around the injector. Could not get engine warm as of course non-runner. I talked to the garage as to this point I had done no damage to injector or cam cover. I wanted to call in a specialist or buy in a suitable tool. The boss decided he wanted the car back.I talked to one of the lads later on, as far as I could glean from him the top eventually came off the injector and they then towed it to the Honda dealership. So far my bill is over £200 for diagnosis and stripping, the injector is £405, plus their time plus whatever the Dealer wants. I bet the head is going to end up coming off because they would not give me the time to “make haste slowly” and get a specialist in. If the customer had bought a petrol car they would be driving it right now, I hope the fuel they have saved pays for the repairs but I doubt it.

I think you are agreeing that it IS possible to deal with the problem of unreliability of electronic components. With bulk manufacture, it need not add a lot to costs. A car is a mechanical device and the engine and other components will wear out, so I don’t think it is financial suicide to tackle the problem. But it is crazy that owners are faced with expensive repair bills or even a car that is not economically repairable because of problems with warning lights or other electronic components that have failed due to poor design, or use of inadequately specified components.

I could complain about other deficiencies of manufacturers and their dealers but the motor industry is leading the way with extended warranties and goodwill repairs – something that washing machine and vacuum cleaner manufacturers would do well to copy.

steve says:
7 March 2013


> Cars are a consumer product, manufacturers would be commiting financial suicide to make something that lasted forever.

I guess it hits the nail on its head partly. This is exactly what the consumer should demand. The consumer should also demand not to be a mere consumer so in fact he would re-engineer it if the initial product is below standard. that’s what I do privately.

But yes I agree that most people treat cars as throw-away products (which in disagree on…).
However I partly blame the lawmaker for this situation: scrappage scemes, unfair LEZ rules e.g. are designed to de-value complete vehicles (even good ones!) in order to help the industry (the big ones only of course…). And it’s being sold as something “green”…and people believe it.
That’s where it all goes wrong.

I’m running a 1987 T25, TD. Runs on cooking oil and with particle filter and EGR is can well achieve Euro-4 even on NOx. But no…the costs to get this certified are just prohibitive.
Used cooking oil + DPF + Catalyst etc. could be one of the ways forward to move away from the oil industry.

Oh and yes I’ve also had a few “spaghetti-injectors”. Twist them, try to pull them, might break the cover…
I always recommend to take the plastic cover off the engine so one can see the injectors. If there’s any blow-by you can get on to it early. Mercedes calls a carboned engine the “black death”. Happens on old Sprinters pretty exactly at 300,000km unless taken care of before.
But a non-runner is a financial desaster, not a safety issue.
And a diesel is still better then a petrol because it’s more efficient and lasting with all its above mentioned potential (…if all this is what you want).

Response Diagnostics says:
7 March 2013

@Wavechange, I think you are missing the point. All electronic devices are still mechanical. I don’t mean this in the context of moving parts but in the context of mechanical assemblies with soldered connections, thousands of wire bonds both gold and aluminium, semiconductors, passive components, transfer mouldings, circuit boards or ceramic substrates, the list goes on. In the light of this apart from documented design flaws with some systems this stuff is extremely reliable, there is just a great deal of it. Imagine the thermal shock when an ABS unit wakes up in the morning at -10degC and the first ABS event raises the temperature of the driver transistors inside by say 80degC within a second. Yes, bigger capacity components could be fitted but then the costs go up and the maker would have to delete a couple of cupholders to pay for it, the customer doesn’t know what trade offs are being made to fit frivolities into the budget for their vehicle.
@Steve, I’ve worked on enough Common rail stuff now to know that it seems to be extremely reliable up until about 100,000 miles then it seems to suffer a complete metabolic collapse with loads of things going wrong in short order.
Whether or not it’s a financial disaster is of course the cost of spares, we all know a common rail injector does not cost so much to make as to justify £400 each, which is the price Vauxhall want for a Denso injector for a Combo van. £150 would be about right.

I am not missing the point since I understand the challenges very well. As for temperature, anyone with the most basic knowledge of electronics knows that components will be more reliable if they run cool.

As you say, electronics can be very reliable apart from the design flaws, but these can be identified and corrected. In industrial process control it is common to employ multiple sensors so that an individual failure is not a problem, but I’m not suggesting we go to this length.

But what is wrong with pushing for manufacturers to pick up the cost of repairing faults in warning light systems? That would provide an incentive for them to sort out their design flaws.

Bob James says:
7 March 2013

@ Steve,
“But a non-runner is a financial desaster, not a safety issue.”
Perhaps that thinking is too widespread, folk are killed on Motorway hard shoulders etc after stopping with a faulty vehicles or punctures, the latest person not so very long ago, vehicle stationary but run into by a HGV. (TPMS soon to be mandatory all new cars)
A MIL light can be indicating a minor problem which left ignored can become more serious sometimes causing the vehicle to engage what is known as limp home mode, drive like that for very long and depending on the fault a flashing red may occur followed by engine failure.
What started as a minor event can now become very serious depending on where the failure occurs, there is no situation where warning lights can be ignored.
Forensic examination of vehicle electronic systems can divulge a surprising amount of information, such items as vehicle speed when codes are set, how long or how many miles driven with MIL illuminated etc etc, we are lied to regularly about such things but the information is there.

Despite the anecdotal remarks we hear there is no hard or proper evidence of warning lamp circuit failures being an issue, we certainly do not see them and we do see many faulty vehicles. Costs incurred as a result of lights indicating genuine problems are an issue and we read plenty of such comments.
@ Wavechange
It is totataly unrealistic to expect manufacturers to design build to a higher standards than are necessary, where is the evidence of all these failures you write of?
Modern vehicles are far more reliable than they have ever been, and much of that is down to those who legislate as are the cleaner emissions, availability of emission information to anybody with a basic OBD scanner etc.
Manufacturers build and design cleaner and thus more complicated cars because they have to not because they choose to but one downside is that sometimes newly designed kit fails prematurely, we have a Megane in the yard, CR diesel less than 100.000 miles that will not be shaking its ass again, a Focus similarly afflicted recently went off to the crusher again less than 100.000 miles, both cars less than 7 years old.

Dave Evans writes of a fault incurred by a possible battery disconnection, there are procedures specified for many vehicles on battery disconnection, some need ecu resets or other procedures to be followed on reconnection, he does not mention whether such care was taken.
Folk, in most cases, only need read their handbooks, quite often the least used item in the vehicle.

Bob – I am not expecting manufacturers “to design build to a higher standards than are necessary”, but simply to ensure that their warning light systems are reliable. If the manufacturers are responsible for the cost of repairs for at least ten years, this is what will happen. If there was not a problem with warning lights, Which? would not have published this Conversation.

Why should we need to use an OBD scanner when information about faults could be presented on the display panel present in most cars?

Let us look at these issues from the point of view of the consumer – the one who has to pay the bills.

I am very grateful that modern cars are much more reliable than they used to be. As an asthmatic who used to be affected by vehicle emissions in cities I am very conscious of improvements, particularly the introduction of low sulphur fuels and diesel particulate filters.

Steve says:
7 March 2013

@ Bob: I guess one can make a safety issue out of anything, maybe even include the correct type of engine oil as wrong oil can cause bearings to fail and if this happens on a motorway you can be a danger to others. But how far do we fetch our arguments…?

I guess the main issues here are:
– loss of authority over ones own property through how systems are designed;
– law makers which de-value vehicles through legislation so owners don’t see the value anymore and neglect repairs
– inconsistancies in the system if e.g. a yellow light leads to an MOT failure but tyre pressure might be more critical but isn’t checked on MOT unless it’s badly down
Many vehicle I see got the pressure down at least 1 bar.
– manufacturers which are not interested in long-lasting products (old story. Google “light bulbs”+”planned obsolesence”).
– manufcturers which are also not interested in simplifying the way fault codes can be diagnosed.

We’ve seen law makers tightening rules more and more but often these rules are just unfair (just think of the LEZ…).
So I still blame the law makers. If rules were better, more people would be encouraged to take self-responsibility. It’s true not just with regards to vehicles. One can’t blame Starbucks for tax avoidance if MPs didn’t do their homework…

Bob James says:
7 March 2013

@ Wavechange
This item was published to highlight the fact that long proposed changes to the current MOT legislation comes into force, actually on March 20th 2013, not as published above, these changes were supposed to have come into force last year but due to legal problems have been on hold till now.

One anecdotal comment regarding an ill defined warning light problem is hardly something Which might be promoting as a problem issue.
Check with the likes of Kia, 7 year warranty on the Cee’d etc, it is possible to find cars where you have a certain amount of the cover you wish for, incidentally this is regarded as a useful car life by a certain French manufacturer we have spoken to.
Just take a look around and see where the manufacturers are at the moment, mass market car makers are in trouble, some big trouble, Jaguar Landrover are taking on more staff, higher quality vehicles are in demand, perhaps the adage “you get what you pay for” is working here.

Bob James says:
8 March 2013

@ Steve
“@ Bob: I guess one can make a safety issue out of anything, maybe even include the correct type of engine oil as wrong oil can cause bearings to fail and if this happens on a motorway you can be a danger to others. But how far do we fetch our arguments…?”

Far enough to save lives, people are dying on our roads every day.

“I guess the main issues here are:
– loss of authority over ones own property through how systems are designed;”

You have total authority and responsibility over and for your vehicle, who it is bought from, how it is maintained and who looks after it, it is not expected that everyone is competent to repair their gas boilers etc and it is much the same with their vehicles.

“- law makers which de-value vehicles through legislation so owners don’t see the value anymore and neglect repairs”

You have the lawmakers you vote for.

“- inconsistancies in the system if e.g. a yellow light leads to an MOT failure but tyre pressure might be more critical but isn’t checked on MOT unless it’s badly down
Many vehicle I see got the pressure down at least 1 bar.”

The MOT system is no more that an attempt to safeguard people against those irresponsible enough to run around in unsafe vehicles, a vehicle presented with seriously underinflated tyres serves to demonstrate that the user should not be in charge of a vehicle on the highway.
Generally a properly maintained vehicle should not be presented for MOT with any warning light permanantly illuminated, driving around with a known steering or brake fault is classed as dangerous driving.
Perhaps the system should go further and report registrations of such neglected vehicles to the relevant authority!

“- manufacturers which are not interested in long-lasting products (old story. Google “light bulbs”+”planned obsolesence”).”

Why should they be?, a large number of people demonstrate quite clearly their intention and need to buy cheap and cheerful low value short life goods from China and elswhere, cars are now available from China here too.

“- manufcturers which are also not interested in simplifying the way fault codes can be diagnosed.”

Again why should they? would you have the patent system abolished too? these systems are designed by engineers and are owned by the relevant companys, the amount of data available from those companys far exceeds what you might obtain on most every other piece of technical kit you own.

“We’ve seen law makers tightening rules more and more but often these rules are just unfair (just think of the LEZ…).
So I still blame the law makers. If rules were better, more people would be encouraged to take self-responsibility. It’s true not just with regards to vehicles. One can’t blame Starbucks for tax avoidance if MPs didn’t do their homework…”

That is passing the buck, we put in place those running the country, hold them to account! Vehicle users are responsible for the vehicles they take onto the highway and increasingly try to shift their responsibility onto others, we see many neglected vehicles and over the many years I have been in the motor trade this has become an ever increasing trend,
it generally is nothing to do with money but changed priorities, a new iphone 5 or fix the car properly, no contest, sod the car.

How many “MUSTS” do most people attend to on a regular basis?

Peugout Owner says:
14 March 2013

Well I come to this discussion as a layman.
My Peugout 307 has the warning light ASR/ESP not functioning. This comes on everytime I turn the car on and then disappears. I have taken it to 3 different garages and spent over £500 trying to have it mended and to no avail. Each garage then just says they have done their best and they are baffled and can do more without charging a lot more money!
The new MOT directive comes in on 20th March which will mean that my car will fail its next MOT and therefore be a write off. Otherwise the car is in show room condition.
I am utterly fed up with garages saying they have the equipment to diagnose the problem and deal with it to then just hand me a back a car in the same condition with a big bill. i have simply thrown money down the drain.
So it is with great interest that I read all your above topics defending your position of charging so much to diagnose problems. If you take the time to read other forums (particularly Peugout and Citreon forums) you will see I am not the only one with such issues concerning ESP lights etc..
I would be happy to have spend the £500 if the car problem had been solved but it hasn’t.
SO can anyone tell me how to disconnect the ECU so that the warning light won’t appear and will my car pass the MOT if I do this?
I await with great interest for any replies!!

Bob James says:
15 March 2013

I can understand your frustration, it is unfortunate you own a vehicle which as it ages is known to be ridden with many faults, a good number of 307’s have prematurely expired due to the high cost of repair.
The main fault lies with PSA, they produced a poor vehicle on which with their own diagnostics system is not at all easy or quick to determine faults, basically if a code is shown it means there is a problem somewhere in the vehicle and sometimes that is as good as it gets.
Your very common ASR/ESP faults can be caused by a variety of known problem items from brake light switch, wiring connectors to a Diesel Particulate Filter etc, the DPF would be an expensive part to change and still no gurantee of total success, hence reluctance on some peoples behalf when dealing with this car.
The costs attached to investigating and correcting faults on this particular vehicle can be high, perhaps this and problems with other PSA vehicles goes some way to explain their present problems, customers buying elsewhere.
You mentioned reading forums where the many known problems with this vehicle are discussed, you might also have noted the frustrations are not confined to just the owners.
As for turning warning lights out, best of luck with that one.

Steve says:
17 March 2013


“But how far do we fetch our arguments…?” ‘Far enough to save lives, people are dying on our roads every day.’

Good point but it doesn’t answer the question. One would still need to decide what would save lifes and what not. You could go as far as to say that all modifications on a vehicle are prohibited unless approved by an ECE type approval- which of course nobody could really affort apart from the big manufacturers (who would welcome this idea). So an additional socket inside would be illegal (pot. fire hazard). But does this make sense?

And where does driver/owner’s responsibility start?
Some peope here would stop immedialtely of their ABS light comes on because their are in fear of not being covered by insurance, then being illegal etc.
In fact you could end up with a shorter braking distance for a while. You might be held responsible if there is an accident which could have been avoided by having an active ABS.
Here then comes your self-responsibility. You are only back to let’s say the 1980s where you’d have to adjust your driving and your reaction on slippery roads.There’s enough time to shop around, find the right tools and educate yourself if you like to fix it yourself, no reason to panic.
There is a certain over-reaction in this country, just like when they all went queuing for petrol like in the 3rd world when tanker drivers were just *considering a potential* strike.

What if manufacturers come up with a yellow light that tells you about a fault with your radio? You’d fail MOT (or quietly disable the light) !

Or think of the low coolant light: No danger for anyone. I’ve seen melted cylinder heads- a financial disaster, very annoying. So I don’t want to be without this warning. Often it’s just the sensor that plays up or a broken wire. But why fail MOT for it?

I miss the common sense in it. It can create too many nonsense MOT failures.

Warning lights are helpers not grumpy policemen who just want to take you off the road (whereas 99% of all police are very common sense people).

As for own authority over your vehicle: There is WIndows and there is Linux.
When you buy a car it’s Windows- proprietary. You will need to invest a lot of time and money to understand the systems and work it all out. Some people manage to turn it into Linux.
But Linux is open source, so bad for profit. MS is trying everything to prevent it from speading.
Remember that manufacturers had to be foreced by an EU directive to open up their repair knowledge bases?
With Linux though you need to know what you are doing if you don’t want to mess it all up. That’s called education and should be encouraged. Manufacturers don’t like it as it’s bad for profit. We should be only consumers and buy (so they can secure jobs- as they argue towards politicians…and offer them a nice job as a later career). So some laws are made to push the public towards Windows- whereas Linux is actually more stable and secure which is why most large servers are UNIX based, and coach/lorry electronics are different.

Just as with health & safety (which in itself is good) there has been too much recently that just wants the public to be compliant by the letter to all kinds of blanket rules assuming they are all dumb consumers. And I guess they will all get there in two generations if being treated like this.
How can self-responsibility be encouraged? Not through rules like these…


Smaky says:
26 April 2013

If your near Oxford then feel free to message me, I’ll plug it in using the Pug OEM equipment and diagnose it for you for mothing, diagnosis using a computer is the simplest thing in a technicians arsenal nowadays, I’ve been in the trade over 25 years, I’m also a licensed aircraft technician and would disagree that electronic faults are harder to diagnose, I’ve found that if the mechanicals are doing what they are meant to then 99% of the time it’s simply a plug on the loom or connection on a circuit which is at fault, and the way cars are today, those are the easiest things to fix.

Bob James says:
16 March 2013

As of VOSA special notice 1-13 it has just become clear that an inoperative SRS light has been withdrawn from the latest (20/3/2013) MOT requirements, if the light illuminates and shows a fault is present a refusal should be issued, if the light is faulty and does not work at all then a refusal should not be issued.
Requests to remove warning lights are no doubt to be expected…