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Discussion Starter #1
Replaced the oxygen (lambda) sensor in my 2003 1.4 16v Renault Clio (probably) due to dodgy fuel damage but the 'Toxic fuel warning light' is still showing on my dashboard.

Car runs fine with new sensor but this damn light will not go out! No other obvious symptoms & all coils currently good...

All dodgy fuel gone and car, with new sensor, running fine...

Mechanic said light will re-set itself after running for a few miles as management system has to re-calibrate (or something). Any ideas how long this should take?

Can obviously call mechanic back but if it's something that can be sorted easy/or will sort itself then that will be better! Will disconnecting the battery reset the ECU?

Cheers...
 

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Disconnecting the battery should reset the ECU so that would be the first thing I would attempt. Leave it off for about 10 mins then reconnect. Post back with an update.

NOTE: make a note of radio codes etc. before disconnecting. As you will need to re enter after. Check the threads in the Clio FAQ (link in my sig) if you need info on this.

Good luck, keep us updated.
 

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Which sensor did you replace?.

If you have had contaminated fuel then it could be either of the Lambda sensors or a damaged catalytic converter causing your fault.
 

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Discussion Starter #5
Hi Lagdti, it was the front Lambda sensor that was changed. Car was running like a bag of nails, sensor changed, car runs fine now...

Bad fuel was assumption because of recent problems...

Would either of other faults you mention (rear sensor & cat) cause a running issue? Or as the car runs fine now, can these be discounted as a reason for light still lit?
 

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As tomandjo above, I think the light might need to be reset.

As Chris has suggested, disconnecting the battery might reset the light, but if it doesn't then it will need to be reset on a diagnostics.

The ECU will relearn all settings, but it shouldn't be reporting a fault as such now as the sensor has been replaced (unless of course there is also another fault present)
 

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Discussion Starter #8
Well, the battery is disconnected so... lets see what happens when I re-connect it!

I am hoping there is not another fault, as I said the car drives fine now however, if the sensor/ecu does need calibrating manually what are my options - does it need to go to renault or can other people do stuff like this?
 

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Actually your car may seem fine but whilst you have a warning message your ECU will be in safe mode, which will mean reduced power and rev limited to 3000rpm (aprox)

Tom
 

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Discussion Starter #10
Not noticed anything like that Tom. sensor was changed yesterday, been driving around fine. Actually gave it a good run this morning (hoping to clear the light) and does not seen to be lacking power or rev limited...

I will check that again when I re-connect the battery but pretty sure...

Gets stranger all the time!!!
 

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Discussion Starter #11
Battery re-connected after an hour and light still showing on dash! arghhhhhh.....

Just drove it and it certainly aint in safe mode Tom, got revs up to 5500rpm, power good and no splutters, misfires or anything...

I will leave battery off again for a while longer but... any other ideas guys???
 

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With the warning light on, it won't necessarily be in safe mode - that would depend on the severity of any other problem.

No harm in leaving the battery disconnected for longer and trying the car over a 100 miles or so, but I think the best way forward after that will be to get it booked in for having the light reset, at the same time ask them if anything else is recorded as being faulty. And you DON'T have to go the dealers for this... any independent with the diagnostics computers can do it.
 

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The fault is still present,then.

If you have changed the upstream Lambda sensor and it runs better,but the light is still on,then there has to be a fault somewhere.

Have you had an emissions check done?.If not,then it's the next thing I'd do.If the cat is damaged then the downstream sensor will pick this up and throw the light on.

It could be the downstream sensor is damaged and telling lies,or it could be the cat that is causing the problem.I'd have an emissions check and code read done and go from there.
 

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Discussion Starter #14
Cheers TazzyK, that really helps... Knowing I don't have to take it to Renault (it's not just the cost but also the 3 week wait!!!)

Could the light really take 100 miles or so to reset itself? I called the mechanic back and he said it could take a good few days, so seems to tally!

Maybe I am just being paranoid and need to wait and see... just test driving new motor next week and the light on the dash will not look great on trade in!!!
 

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The light won't take three days to reset!

If the fault was fixed,then the light would go out.:(

The ECU can only react to the information it is being fed,so if the lights on it's still getting information from somewhere that is doesn't like.ECU's are stupid,they can only do things when they're told to......a bit like me.:eek:
 

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Discussion Starter #16
Cheers Lagdti, if the cat is damaged will it cause any running problems, what about the back sensor? Will probably leave til next week (with fingers crossed) then find garage to get it checked out - get fault code read, emissions test if needed, and light re-set!

Not gonna be able to do anything until Monday now anyway...

Thanks for your help...
 

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The cat won't cause any running problems until it starts to break up and block the exhaust,but you will get plenty of warning of this(rattle from exhaust first...).The second sensor only checks the cat is working and won't effect the running either...

Good luck and let us know how you get on.:)
 

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Discussion Starter #18
Thanks everyone...

Seems pretty clear that the light is unlikely to clear itself as the mechanic keeps advising and it's useful to know that if the cat, or rear sensor, is faulty then it would not affect the way the car is running...

So, in narrowing it down are we saying that the possible problems are:

1) New front sensor could need manually re-calibrating and fault cleared from ECU

2) Cat and/or rear sensor could also be damaged, requiring further work

I will spend Monday trying to find a garage that can hook it up to a machine of one sort or another - where should I take it (tuning centre/mechanic/fault finding) and what should I be asking for (in relation to what tests need to be done)? Ie: Should I go for an emmissions test or get the fault code read first etc?

Cheers again guys...
 

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Discussion Starter #20
Well, booked into auto-electician for 11.00am today. Got in the car at 10.30am to take it there and guess what? The light went out all by itself!!!

Talk about timing hey? Seems like the mechanic was right - lets see if it stays out!

Cheers for your help guys...
 
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