Resetting/remapping ECU

jrwb

Full member
Points
23
Location
2002
Car
Renault Clio
Hi everyone...I have a question I would like to ask and which some may think utterly ridiculous. I own a 2002 Renault Clio 1.4 16V which is always going into limp mode and no one seems to know what is wrong...it seems Clios like to do this and it is only after a ton of money is spent changing this part and that part that SOME eradicate the problem.
I have been driving too long and( trained in Auto Mechanics) not to know when an automatic transmission is bad, and mine is not.
My question is this: is it possible to REMOVE from the ECU the limp mode feature? Surely this is possible with all the changes people are always making to their ECUs. Some opinions are most welcome.
 
Limp mode is there to protect the engine, it usually comes on when a sensor is picking up on an unusual reading.

Running a car in normal mode when things are wrong can cause serious damage to an engine, even if there is no real fault other than a faulty sensor somewhere.

Have you been to a Renault specialist? I find a lot of local garages adopt a try it and see approach to fixing cars which is costly and time consuming.

Intermittent faults are really hard to track down, you need the full diagnostic suite and the fault to occur while the car is hooked up.

Southcourtgarage.co.uk are pretty good at fault finding but they are probably miles away from where you are.
 
Yes limp mode is there to protect the engine, but in most cases it is due to a defective sensor sending the wrong information to the ECU. It is a damned nuisance where a warning on the dashboard would suffice. A good example is the auto transmission - when it is going bad, three major symptoms usually occur - reverse taking long to engage, slipping and forward gears taking long to engage if at all. These symptoms will always get worse with time and the amount of driving done. Most people who experience limp mode do not have defective transmissions - it is usually something else, and this often defeats the purpose of the limp mode, except to give the driver a headache! The internal combustion engine has been with us for more than 100 years, and its principle of operation has not changed. To actually destroy an engine, you would have to run it without oil, or coolant or over rev it badly. You do not need limp mode for that - a simple warning on the dash can take care of that. Older cars had warning lights/ meters on the dash just for this purpose. All this computer garbage on modern cars is just to save the manufacturers money. During the first few years they are OK and after that the complicated wiring and electrics start to give trouble, and quite often very difficult to correct. On a different note, do you want to tell me the advantage of a timing belt over a chain? The advantage of a potentiometer over a cable/rod for the accelerator? Oh by the way I am an automotive engineer, unfortunately not a computer engineer.
 
Oh by the way I am an automotive engineer, unfortunately not a computer engineer.
 
Limp mode isnt a fault but a function.
Put another way it is a series of settings that an ECU triggers and it does this on the basis of information received. And when things do go wrong the system does work.
But as I understand things the car IS RUNNING FINE AND HAS NO ISSUES but keeps going into limp mode.
Now it is theoretically possible to cancel the limp mode but this may well be extremely difficult to do because the system has likely been designed to stop this happening .
Unfortunately I doubt renault will help for the same reason.
So the next bit assumes you know what you are doing (which Im not doubting)
I assume youve tried resetting the ecu. Maybe you could try a different ECU from another clio that would at least show that it isnt the ECU.
Assuming thats been done if it were me and I was ABSOLUTELY SURE that the car is fine I would look at the sensors that trigger the messages that trigger limp mode because stopping the sensors sending the info will stop the limp mode.
I have done this with a warning light which is the same principle though the wiring may be more complex
Hopefully you dont have a canbus system - If you have then the next bit probably wont work but if not..........
Try to find out out what signal they send - you may be able to do this using a multimeter
If you are lucky some will only send a message when they sense an abnormal reading . In that case you can disconnect them . Of course you then would lose the protection so do this at your own risk.
Some send a simple signal which changes when there is a problem . If you can find out what the signal (might be for example 2.5v ) . You may be able to send that "all is well " message by sending the normal signal from another source This would also work if the sensor has a range .

Needless to say any or all of the above is completely at your own risk.
 
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Thanks for that advice...must be a sensor or something, because the transmission works reasonably well...if it were on the way out, it would have done that ages ago. So you see. if there was no limp mode, there would be no problem; it is like being punished as a child for something you didn't do. Here in these backwoods there is no Renault dealer, and one has to find people who one thinks know something about the car, which is not always the case...
 
I appreciate your frustration with this.

Do you have access to a fault code reader? That would help diagnose which areas to focus attention on.

On Bosch ecu's the limp home mode is in the hardware, remapping software runs outside of this area. It helps protect against a variety of mapping errors, fuel issues or engine hardware issues. I don't know of anyway to switch off this protection.

A computing degree is fast becoming a requirement in car ownership. :(
 
The limp mode is a design feature designed to get you to a service facility in the event of a fault. Your best option really is to connect an OBDII code reader to the car and see what is actually going on.
 
Absolutely correct of course HDi but I was assuming that a trained auto engineer who is trying to rewire around an ecu fault has actually at least put an OBDII reader on it first . If he hasnt my previous suggestions will be way over his head.
However assuming he has and they are not................
Im pretty sure you can tweak a map to avoid limp mode .
And once the ecu has received the info supposed to trigger it only a reset or fixing the issue will work.
But if one could cut the supply of that info to the ecu that should stop it going into limp mode.
of course in theory isnt the same as in practice.
 
Agree with Sleeper here.

Not entirely sure about suppressing the sensor signal though. I think the ECU code will very likely consider the absence of the sensor, or absence of its 'fingerprint' to be a fault condition in itself and thus still engage limp mode.

For example, if a wheel speed sensor goes offline, or reports 'impossible or inconsistent data' the ECU will disable the ABS and its associated functions, together with presenting the driver with a yellow or red ABS fault warning lamp. This is the reason that the ABS warning light function and sequence forms a part of the MoT test in the UK. If the light is permanently on, whether or not the system is functioning correctly (I suppose we should really consider the fault warning system as part of the greater system anyway), then the system has no way to alert the driver to a fault if one occurs. Incidentally ABS function itself is not part of the MoT test.

If we totally suppressed limp mode (with a very aggressive sweeping change to the ECU) we could wind up with a car that destroys or damages itself at best. At worst it causes accident or injury.

There is no harm in resetting fault codes in the first instance. If the code does not represent itself then we can consider the fault to be temporary and the issue can be dismissed for all practical purposes.
 
actually a huge typo I meant to say Im pretty sure you cant tweak a map (not can ) to avoid limp mode.
All this discussion is based on the ops premise that THE SENSORS ARE WRONGLY MAKING THE ECU GO INTO LIMP MODE.
If that isnt the case thats whats limp mode is for
So if a sensor is sendimg the wrong signal sorting this would be fine in the short term and only till the sensor has been changed.
 
That is not so at all...suppressing limp mode is not going to destroy anything provided the driver monitors his instruments. Before cars had ECUs people didn't go about destroying their cars - they simply monitored their warning lights or gauges. I am inclined to think that in the future there is going to be a drastic reduction in all this computer nonsense in cars simply because they are over-complicated, and when the car starts to cross ten years they can be a real headache. Cars are now developing problems they never had before - like defective sensors which actually create a problem when there is nothing wrong with the car (except the sensor, of course). As far as reverting to the old ways is concerned - I have heard Nissan has started replacing timing belts with chains in its engines - don't know if this is true, but if it is, it's an excellent step. A rubber belt for such a critical function is crap. Just look at the scores of wires connected to an ECU in that super hot environment and tell me if this isn't going to cause problems later down the road. Our laptops and tablets do have complicated circuitry, but they aren't often subject to the conditions found under the bonnet of a car. An electric throttle seems to me to be quite unnecessary - I have heard that when they go, the vehicle will only idle - this seems to be one good use for limp mode if it is applied to this problem. A good idea is to give the driver the option to overide limp mode from the drivers seat, or to simply turn it on manually when he notices a REAL problem with the car. All over the internet one can find motorists complaining about limp mode in their vehicles when, according to their descriptions of the problems, there's actually nothing wrong with the car - only misinformation sent to the ECU.
 
i tried to be helpful but its clear most of your thoughts have no basis
you cant back up a statement with 'ive heard, or ,'over the internet'
some corrections
1 timing belts are not rubber and they are not crap . My timing belt only needs changing every 70000 miles and thats on a engine producing over 200bhp per litre that revs to over 9000rpm which is a ...............................nissan
2 ecus do not give problems because of the numbers of wires
3 ecus dont suffer because of hot bonnet conditions because ecus are not fitted under bonnets
4 engine performance improvements are a lot to with ecus - they are hear to stay for sure .
5 And if your throttle cable breaks the engine only idles as well so no change there
 
You seem to know little about cars except your own. My reference to what I've heard or seen on the internet is a rudimentary form of a survey in which people express their experiences - quite acceptable in many circumstances...owners' surveys and all that.
1 The timing belt change you mention is manufacturer's recommendation - they have frequently been known to 'strip' teeth before recommended change (they don't normally 'break') and obviously a chain is stronger (please don't argue about a recognized fact). I used the term 'rubber' loosely - they can be made of neoprene or polyurethane.
2 Based on the laws of probability, the more wires there are, the more chances of one or more of them developing a problem.
3 Again you know little about cars - many manufacturers fit ECUs under the bonnet, others in the cabin.
4 Possibly, but manufacturers are known for doing things they eventually realize are rubbish after saving money and revert to the previous arrangment. It is possible we may see a reduction in complicated electrical components in cars.
5 If your physical throttle should break, it is possible to 'tie it up' with something, you cannot do this with an electric throttle. I have actually done this.
 
"You seem to know little about cars except your own. "

I gave the example of my car was because it is a Nissan so absolutely relevant to your completely unsupported statement about ...........nissans

I prefer facts as they are proven unlike sweeping generalisations and statements based on hearsay such as

manufacturers are known for.....
they have frequently been known to.......
I have heard Nissan has.......
It is possible we may see a reduction in.....

I would also be interested in which manufacturers put theit ECUs under the bonnet near or next to the engine.
 
To jwrb:

The collective level of knowledge and experience on this site is phenomenal. It would be a shame to disabuse your self of this Likewise it would be a shame to deprive others here of your experience and knowledge. No one is out to disparage you. Come on mate, this is a friendly and diplomatic place where things get done in a convivial and enjoyable way.

I fully sympathise with your frustrations that your car is causing you. I have had cause to rage at my VW many times - I think we mentioned this a few days back; all in good humour.

I would like to add though, electronics are in general highly reliable, it's just that because of the relative absence of issues in general when one occurs it's a bit of a surprise.

Your point about lashing up a mechanical throttle with a piece of string is a sound one. (I've done this with a Montego many years ago!) But we could conjecture that a fly by wire throttle arrangement has no mechanical cable at all, which is one less potential failure point. I do, however, concur with your points about timing chains over belts. 100%

I don't think we will ever see a return to more traditional methods and designs, principally because of the very restrictive legal requirements made in terms of emissions and safety. Progress is generally a good thing. Would we want to return to drum brakes and crossply tyres? I suspect not.

Yes, there are some manufacturers who are not as adept at design and construction as others, but these could equally make a mess of a mechanical system just as much as of a digital system.

Also, car makers are not colluding to make things difficult for you, nor for anyone else. After all, they all want our business in the form of new car sales volume. Reliability and reputation are big factors because it's used value or trade in value which dictates how much a customer can spend on a new car, how much they can charge for it, and what make and model this customer elects to buy.

So can we please get the ball back on the floor, so to speak, and start helping you unravel this problem your car is presenting to you.

No one here is setting out to make digital enemies, genuinely.

Best regards,

Paul.
 
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So, I'm not supposed to say that I heard something, or perhaps an opinion - are we in a court of law? Well, my friend this is a universal trait of human conversation. Where I heard something, I have said so, and not treated it as fact. Opinions and suppositions are extremely common in human communication - as a matter of fact they are quite necessary when making decisions and predictions. Renault and Jaguar (not sure which models) place ECUs under the bonnet - look it up, I am not an automotive encyclopedia. My Clio has it right next to the engine. By the way we are having an informal conversation - it is quite normal to give opinions and quote others - but as I say, I did not walk with a folder with all the facts that I can quote like a lawyer in court - this is supposed to be an informal chat...isn't it???
I do have two examples of features ditched and re-introduced in modern cars - rack and pinion steering and superchargers. Also wheel rim sizes - almost the size they were in the '30s and '40s. Door handles now closely resemble their predecessors of the fifties and sixties. Mercedes-Benz had stopped putting dipsticks in some models; I understand they have started putting them in again in response to owners' complaints. Jaguar - in the XJ40 - had originally installed digital instruments, and had to change back to traditional anologue instruments because of customer complaints. Push-button start has also made a comeback in some models.
 
Have a google for error lights as in some ECUs you can get it to flash the eml or another light so many times to give you the code - so say it flashes 3 times, then pause, then 5 times, the code is 35 and then you can just google that code.

Vauxhalls can do this - at least the Vectras and Signum I had could.

And I also have fond memories of fixing the accelerator cable with a string. (;->
 
No, I don't want cross-ply tyres and drum brakes in my car - although for normal driving it is hard to spot the difference between discs and drums when the latter is equipped with a good booster...
 
Everybody is giving different opinions as to why the limp mode is coming and going - the problem is you do not know where to start and this could cost a helluva a lot of money changing this part and that...
Perhaps it might be a good idea to dump the whole engine and tranny and install a Nissan unit (an exchange popular here in Trinidad).
 
I do sympathise with you, no one wants a tryit and see if it works approach...

So going back the original topic and totally sidestepping the minor semantics debated here....

Have you looked at fitting an aftermarket ECU? Apexi, Megasquirt etc... That might be a way to achieve what you requested in your original post. Some of the aftermarket ECU's don't even run a knock sensor feature.

AFAIK you can only change the mapping and timing and boost levels in an ECU, the back end firmware is locked away usually and not to be touched.

Have you spoken to a remapping specialist? They might be able to shed more light on this.

The engine swap does sound like a good idea if you can get the parts you'd need to pull it off.
 
We no longer have a Renault agent here, and engine and transmission swapping is very popular. The Nissan engines are cheap and reliable. An after market ECU would be dreadfully expensive (like everything else here in Trinidad).
 
I think Renault and Nissan have been using each others engines for some years. I also note that I had a Primera with the SR20De petrol engine back in 1997 (new) and that was a chain driven unit. The Nissan engines are largely bullet-proof, it would take some serious neglect and systematic abuse to damage one.

BMW has never entertained belts at all, to the best of my knowledge.

The rationale behind chains is a good one, and I agree with you completely on this point.
 
I changed my belt several weeks ago, but that obviously is not the problem - the auto transmission works reasonably well, but I can't seem to get the engine to run properly - it idles badly, and in the 1500 to 2000 rpm range, it is rough and hesitant - one chaps says injector problem, another coil problem...
 
I changed my belt several weeks ago, but that obviously is not the problem - the auto transmission works reasonably well, but I can't seem to get the engine to run properly - it idles badly, and in the 1500 to 2000 rpm range, it is rough and hesitant - one chaps says injector problem, another coil problem...

This is why you really need the OBDII codes read. They are pretty granular. It will even give the cylinder number that is at fault in many cases. Frustrating though, isn't it? I've been through similar issues myself - totally understand that you simply want the problem resolved. You can test the coils with a DVM but you still need to reset the fault codes subsequently.
 
+1
as i said in an earlier post check the fault code in the ecu before looking at anything else if neccessary with a code reader


Chains..........
All I did was disagree with the statement "rubber belts for this function are crap" and gave an example of one lasting well in a high performance engine.
That doesnt mean that I said chains are worse , infact i never mentioned them . So for the record , of course chains are good and Im happy to agree that in some ways they are better than belts . But that in itself doent make belts crap.
Re ecus and wiring - less wires are not always better - canbus proves that - An example of new technology being theoretically better but a real pain when it goes wrong .Here I agree 100% with the op about new electronics not being the be all and end all.
Funnily enough canbus was designed to cut the number wires down (theoretically good) But to do this more than one signal is sent down one wire .This is a brilliant concept but when you have an issue its an absolute nightmare to sort. Id ban it , but of course it will never happen because manufacturers are only concerned about new car specs , they dont give a fig about reliability when the car is ten years old.
The problem is that by definition better ecus have to cost more because extra functions = extra programming = more processing power = more cost
And I couldnt agree more about limp mode . Ive had it removed on my car. Happy to explain how but it isnt a simple
It does means more wires, sensors and a 32bit or better ecu which is self monitoring . Then it can solve problems on the fly - so no limp mode needed
After all limp mode is merely a simple way of avoiding damage by cutting out most functions rather than locate the offending one and thats one of the limits of an 8 bit ecu .
 
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to the OP:

ODB2 code readers are readily available from Ebay and other retail sites. I have a VW specific one. Circa fifty quid. Well worth the investment.
 
to the OP:

ODB2 code readers are readily available from Ebay and other retail sites. I have a VW specific one. Circa fifty quid. Well worth the investment.
I have a Bluetooth odb of eBay less than £5 and the paid version of torque app on Android. It works on the majority of vehicles
 
I was just pointing out to the OP there is a cheaper option than the £50 vw specific one you mentioned Paul;)

What I meant was that I,too, have the $5 Torque app for Android and a ELM327 Bluetooth OBD2 interface.

As well as the VW specific device.

I don't really understand why the OP's is so reluctant to read the diagnostic codes.
 
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I have been trying to use my laptop to scan my car, but only one of the programmes seems to work - do some of these OBD2 apps have to be ELM327 specific?
 
I think in some cases yes. I wish manufacturers would stick to the standards set down (ie OBD2) amongst themselves rather than each creating their own subset or superset of DTCs.
 
...I had a man scan my car a few weeks ago and he charged the equivalent of 10 pounds, got one code, misinterpreted it, and I actually connected it and did the reading! Others here in Trinidad can charge as much as 3o pounds for the scan. That's why I got a cable (it says ELM327) to do my own scans. Most of the progs say 'can't find interface' or 'failed to connect'....etc.
 
Those replies mean it is not recognising your car and/or does not have the ability to read faults for that car
This is a problem with some of the cheaper "ebay scanners" - sometimes they are just that and although they are supposed to be programmed for all models they are not - Maybe your man was using one of them

I bought a cheap ebay one and it works fine on all the uk cars ive tried but on quite a few of the cars Ive imported it just doesnt work or only works for some codes.
My caldina just doesnt get recognised at all yet with some nissans it will work fine but on others it will only give some of of the codes .I had one with a speedo sensor fault .I know because ecu flashes code 55. But the reader misses it completely but will find an abs speed sensor fault .

As to charges when you remeber that they have had to buy the equipment and drive out to see you (and back ) £30 doesnt seem to bad to me .(just IMHO)
 
£30 is good. A full dealer quality diagnostic device costs in excess of £3000. These are far more granular than consumer oriented devices such as mine.
 

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