E39 528. Has now passed all the MOT tests, bar the 'Natural Idle Test' CO level at 2000 revs is a Pass, and Lamda is also a Pass. The last item on the test sheet is simply CO Level 0.85 %, which is also a Fail. I assume this just refers to the Natural Idle Test.
Failed on the same points the first time, so on the advice of the tester and the garage that did the work on the brakes etc, I bought 1 new Lamda sensor which the garage fitted today. It made no difference, so the 2nd sensor was changed for the one that had been removed, on the basis that if it wasn't any different to the new one, it might be the 2nd sensor that was faulty. Still no difference. It would appear that both Lamdas are OK. but CO levels are still too high a tickover I'm going to have a diagnostic check done by my local BMW dealer, who hopefully will be able to pinpoint the fault, but in the meantime has anyone any suggestions of what might be causing the high CO reading at tickover? TIA. Mike.