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Discussion Starter #1
Hi,

I replaced both pre-cat lambda probes today (BARU).
Two months ago because the engine light was lit I had the codes read and it stated faults with both lambda's. ( I inherited the car with this and other problems so don't know its history)

my question is, do I need to have the fault codes cleared or will the engine light go out in time should it sense no further fault?

Cars due for MOT next week, so will probably need have have them cleared if still lit or worse, that a problem still exists.

Regards
 

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Discussion Starter #3
Thanks for that, I thought the problem could lie somewhere else further up the line, will try the diagnostics again, trouble is it seems to depend on how competent the technician is on interpreting the readout results or how reliable the information is, had a number of wrong (and expensive) information given in the past so I am sceptical about how accurate these readouts are.

Some one suggested that it could be the injectors over fuelling and showing up as a lambda fault, any ideas?

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That's very unlikely that injectors will overfuel, they'll usually do exactly what the ECU tells them to do.
It could be cases of air leaks, bad MAFs, holes in the exhausts etc. E39 V8 cats do seem to get changed quite often, but I can't tell if that is a problem, or misdiagnosis.
The E36 for example very has cat problems.
 

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the car will not fail an MOT for having the engine light on but it may fail for the fault it is indicating. before spending any more money on the car put it through the MOT, if it passes then just the light to sort out, if it fails on emissions you have 10 working days to sort out fault for retest after that it is a full chargable test again.
 

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Discussion Starter #6
Well. had the car MOT'd Saturday and it passed okay, emissions were spot on, engine light still comes on after cancelling, diagnostics still display pre-cat lambda probes (both) as the problem, cannot find any air leaks, would the air flow sensor show up on the diagnostics, although wouldn't that also affect the emissions if it was faulty?
I have no idea what the problem is, unless its either an ECU or wiring fault, any ideas.

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I had this problem with my E39 535i changed the MAF and worked fine from then on. If you do replace this be careful where you purchase it from the first one I bought I was told it was the correct one and it wasn't.
 

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Discussion Starter #9
Okay thanks, looks like the MAF is next on the list, well at least the list of possible causes is getting shorter, I'll get there in the end.

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