My 2002 Nissan check engine light will not go out. I've changed the o2 sensor (Bank 1 sensor 1) could it be my computer chip?

catalyst efficiency below threshold bank 1 is a PO420. But i would check the oxygen sensor out first that also will cause a check engine light .A cheap one can fail but to check yours take it out and heat the end with a torch with and check it with a voltmeter. I would google that first if your not familiar with that method.Some vehicals take about 30-60 miles before the code will pop back up but with newer vehicals it will pop the code right away.

I'm willing to bet you have weak upper O2 sensors & there's nothing wrong with your knock sensor. But if you want, the knock sensor is under the lower intake manifold in the back that is located under the upper intake manifold also called the upper plenum. The lower intake manifold is wedged between the 2 heads and is an enormous pain in the azz to get to. You can check the O2 sensors with a scanning tool that will show you the upper sensors in bank 1 & 2 bouncing electrical current from about .5v to 5v several times per second. Anything less show weak sluggish sensors. The resulting lean mixture causes a knock. Change the sensors and the knock goes away and so does the engine light after you reset it. It took me 6 months to find this problem after replacing everything else including the 6mth old O2 sensors fresh from China. Now I have Bosch. PS The lower sensors went 2 weeks later & I was told any more problems it's the fuel regulator. 2001 Frontier 3.3l v6. No problems since, it purrs like a kitten. I'd suggest the Bosch, it's a special design for that 3.3l engine.

Hi Adam, I believe the most cost effective action for you is to get the management system designed for your engine. When doing so it may well be required that you also purchase the wiring harness that goes with the replacement unit. Regards John

I use always scanner I heard to disconnect battery for over 5 min.

O2 sensor/s faulty

P0134 and P0154-o2 circuit not actively detected-bank 1 and 2, side 1

Nissan TSB Reference # NTB02-015 (in canada). Might be a similar TSB in the US-also this;



It does sound like it is an electrical problem, possibly in a harness (damaged) or the ECM had major issues that a reflash could not overcome.

change the o2 sensors and have the codes cleared that should fix your problem

Hi Garcha,

Both codes relate to O2 Sensor # 2

Code P0139: O2 Sensor Circuit Slow Response - Bank 1, Sensor 2
Code P0140: O2 Sensor Circuit No Activity Detected - Bank 1, Sensor 2

A faulty O2 sensor will mean incorrect signals will be sent to the EFI computer, causing erratic engine running.


Cheers,


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code p 0138 refers to 2 items
1--heated oxygen sensor(HO2S) 2 bank 1--high voltage ==causes --wiring short to positive --HO2S---ECM
2--oxygen sensor (O2S) 2 bank 1--high voltage ===causes wiring short to positive ---ECM
code p 0139 refers to 2 items
1--- heated oxygen sensor (HO2S) 2 bank 1--slow response ===causes --heating inoperative --wiring--ECM
2--oxygen sensor (o2S) 2 bank 1 slow response ===causes --wiring --- O2S

heated oxygen sensors9HO2S) are in the exhaust manifold before the cat converter
Oxygen sensors (O2S) are after the cat converter
it is indicated that the HO2S is faulty-
check the wiring and /or replace both sensors

sounds like it , the sensor should be on the exhaust somewhere,whith wires on it