Remapping?

[huwlj3]

My car failed it's mot yesterday, had a diagnostic test done today and apparently it was the lambda sensor. Tested the emissions with new lambda and still CO level was far too high. My mechanic spoke to Renault and they think it has been remapped in the past? Could this be the case? If so, how much to put right?

 

[clio-lane]

Are you sure that your car isn't running a decat or similar exhaust? They can normally tell if the ECU has been altered. I think it remembers everytime it's plugged in to a computer - something like that.

 

[huwlj3]

No decat, was removed for mot and cat put on. No aftermarket exhaust either. Hasn't been plugged into a Renault computer yet. Trying to avoid it due to cost.