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Hi
My 325i (N53 engine) was flagged up at its last service 3 months ago as having an Ageing NOx Sensor.
It sailed thru the MoT but I noticed the CO at idle was 0.3% which is the limit.
Could the NOx sensor be affecting CO emission? The Fast idle was very low CO.
Or could the CAT be on it's way out. All the other parameters were well within limits and there are no codes on the OBD.
Cheers!
I am a very long way from being an expert, but I would have thought that the ECU takes sensor readings from various points and tries to adjust the AFR accordingly so as to remain within emission requirements.
So yes, it's feasible that a dodgy NOx sensor could end up affecting CO readings.
Thanks, It passed the MoT but the CO was on the max (0.3%) so was wondering whether I should sell. I'll get it re-checked at the next service and if need be replace the NOx sensor.
I gather the CO test requires warm engine oil, so I'll be sure to give it a good run before the test; this morning it only did 5 miles prior to the test....