flyboy Posted February 21, 2015 Posted February 21, 2015 (edited) Hi Guys, I have just failed an MOT on CO emissions with the lambda sensor being thrown out on both the fast and slow idle. I have a fault code P2A03 pending which I checked after the fail which reports on O² sensor bank 2 pos 1 which I believe is an air fuel ratio sensor. The question is is it being thrown out of range by the intake system? I can just change it but its an expensive part if it turns out to be something else. Your help would be appreciated. Edited February 21, 2015 by flyboy Quote
flyboy Posted February 21, 2015 Author Posted February 21, 2015 I have just found a small exhaust leak at the flanges half way down the exhaust on both sides. This could be pulling air giving a high Lambda but what about the high CO? Quote
Tricky-Ricky Posted February 21, 2015 Posted February 21, 2015 Did they give you a lambda voltage/AFR or just Co? what was the Co? if the air leak is above the lambda then it will effect the reading, if below by any degree than no, can you get a lambda voltage via Nissan datascan or similar software? Quote
flyboy Posted February 21, 2015 Author Posted February 21, 2015 (edited) Any air leak will be above the mot lambda as its up the tailpipe of the exhaust. The exhaust leaks are below both sensors on the car CO was 0.36% at first fast idle and then 0.73 at second -- passmark is at 0.2% lambda was sitting at 1.08 and 1.09 -- passmark is 0.97 to 1.03 HC is low at 33ppm I have put the original intakes back on and gone for a test drive Using Car Doctor Checking the lambda voltage at steady speed 60mph in 6th (closed loop) and bank 1 and 2 are different to each other Bank 1 was fluctuating up and down in a regular pattern from about 0.9v to 0.2v which I think is correct Bank 2 was a steady voltage with no fluctuation didn't get the reading though. Edited February 21, 2015 by flyboy Quote
Ricey Posted February 21, 2015 Posted February 21, 2015 Are these the pre or post cat sensors you're checking? Quote
Ricey Posted February 21, 2015 Posted February 21, 2015 Sorry just noticed you said it was the lambda I think I'm in agreement with you. Lambda should not flat line. It should gently oscillate. If memory serves that is! Quote
flyboy Posted February 21, 2015 Author Posted February 21, 2015 It could be that it hadn't gone into closed loop if it wasn't hot enough it will then put out a constant voltage of about 0.45 volts in open loop. Ill check it again tomorrow (Obviously this is being done by a passenger as I am busy driving) when I am not struggling with it going dark on me. Quote
Ricey Posted February 21, 2015 Posted February 21, 2015 Aye but you were testing it at 60 mph presumably not from stone cold so it should be into the closed loop by that point......the fact bank 1 was is a good indicator Quote
flyboy Posted February 21, 2015 Author Posted February 21, 2015 (edited) Oil was at 85° so no, not cold. Edited February 21, 2015 by flyboy Quote
Tricky-Ricky Posted February 21, 2015 Posted February 21, 2015 Any air leak will be above the mot lambda as its up the tailpipe of the exhaust. The exhaust leaks are below both sensors on the car CO was 0.36% at first fast idle and then 0.73 at second -- passmark is at 0.2% lambda was sitting at 1.08 and 1.09 -- passmark is 0.97 to 1.03 HC is low at 33ppm I have put the original intakes back on and gone for a test drive Using Car Doctor Checking the lambda voltage at steady speed 60mph in 6th (closed loop) and bank 1 and 2 are different to each other Bank 1 was fluctuating up and down in a regular pattern from about 0.9v to 0.2v which I think is correct Bank 2 was a steady voltage with no fluctuation didn't get the reading though. If there is no voltage variation then lambda is dead, which will account for the fail as the ECU will run fuelling rich by default. I actually meant that if there is a leak in the exhaust above the std lambda, then the ECU will be trying to compensate for the extra air, so this will also screw with the Co that the MOT sensor will see. Quote
flyboy Posted February 21, 2015 Author Posted February 21, 2015 If the mot lambda is high, sensor is reading lean which could be accounted for by the air leak into the exhaust. The nissan lambda is dead sothe ecu runs rich giving high co even though there is too much air in the exhaust giving the false lean is this possible? Quote
Tricky-Ricky Posted February 21, 2015 Posted February 21, 2015 If one lambda is dead the ECU runs that bank rich, so its unlikely that if that side has a leak it will make enough difference, however if the is an air leak pre lambda on the side that still working it will result in the lambda seeing more air so the ECU thinks that it needs to inject more fuel to compensate, so resulting in even higher Co. Quote
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