QuestionQUESTION: Dealership had car said it needed both O2 sensors and knock sensor. Now that all 3 have been replaced ChkEng light is still on. Turning the Diag switch on the ECM while in IGN 'ON' (eng not running) clockW and Back doesn't reset it. When doing the Diag on the ECM still shows codes 91(FrntO2), 92(RearO2), 34(Knock), and 37(closed loop operation error)(butFront O2 is fine). ECM won't reset. Any ideas??? (Leave the battery unhooked overnight?)
ANSWER: Great info, problem here is that I have not one clue as to what vehicle you have here. Sorry! I hope its a Maxima.
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QUESTION: Everything except the car eh? 1999 Nissan Altima 4cyl Auto!
ANSWER: Replace the knock sensor first, they go bad. Then remove the negative battery terminal from the battery and touch it directly to the positive for 60 seconds. Then we need to see if the light comes back on. EH. :)
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QUESTION: With that tried no luck, The light still stays on, and blinks the same four error codes. Let me say again that Both O2 And the Knock sensor have just been replaced. The ECM doesn't seem to see that, nor will it reset so the light is off. I find it hard to believe that All three sensors just replaced are factory defective - So I'm wondering why the ECM won't reset and why it doesn't recognize that (in theory) none of the prior problems have been corrected. Can something go wrong with the ECM? Any ideas?
AnswerI would suspect bad ECM or harness issue. Can you get your hands on a used ECM? Swap it out. I am assuming that you have already checked all power and ground sources to ECM. Remember that the rest are low voltage circuits. Make sure there are not connectors unplugged. Focus on the faulty component circuits.
