Hey guys, been a long time since i posted on here. Had to retire the ssei a couple years ago and i came across this 99 buick lesabre, overall not a bad car, had its typical issues but all was resolved easy enough.

The problem im having now has me stumped i got a p0131 and p0135 the other day so i figured ok oxygen sensor bad, replaced it and it ran great for a couple days then yesterday it started acting up and got the codes again, it was idleing very eraticly and eventually stalled. It will do it weather its in gear or park always resulting in stalling. If i keep my foot on the pedal it will stay running. Also if i have the o2 sensor unpluged it seems to have a stable ldle.

I got the multi-meter out and started probing wires and this is what i found... The signal leads on the sensor itself while unpluged from the car and with the engine running have 800-850 mv and fluctuates consistantly, which leads me to believe the sensor is good. The powed supply and ground for the o2 heater have 11.5v with engine off and 13.8 with engine running, so i believe that to be fine.

Now this is where im stumped, I tested the the signal wires in the wire harnes itself and it registered .38 volts with nothing attached but the leads of my multi-meter, with the o2 sensor conected if i test the signal wires it registers 1.5-2 volts. Correct me if im wrong but i thought the signal circuit of the o2 shouldn't have more than maybe a 1 volt in the case of a rich fuel mix?

One more thing to add, i tested the resistance of the tan signal wire from the connector plug back to the pcm and got 5 ohms, i dont see anything wrong with that, but i couldn't find a diagram showing where the purple wire terminated at the pcm so i used a known pcm ground and tested again from that connector plug (purple wire) to the pcm ground and got 93.5 k ohms. Thats telling me theres a short somewhere...

Basicly what i need to know is am i on the right track? And where does the purple signal wire terminate at the pcm? I know this is really long and i appreciate anyone who takes the time to read through it, I just wanted it to be clear about everything i've tried.

Thanks in advance.
Tom

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If it were quick and easy everyone would be doing it!

update: I managed to find a pinout of the pcm and located the purple signal wire. The resistance is also low at 6 ohms so im really confused now. I let the engine warm up again and checked the volatge of the signal wires at the pcm and it read 3.5 volts. why would i be getting such voltage in the signal wires?? Could the pcm be no good?

On a side note i still have the pcm from the 98 bonneville, would i be able to put that in to test... bonnie was supercharged buick is n/a.

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If it were quick and easy everyone would be doing it!

Hey guys again I appreciate anyone who took the time to read my long a$$ post, I believe i have figured out the problem. I decided to plug my old o2 sensor back into the harness and low and behold, cold readings were normal at 0.00 volts. So I swaped the sensors out and car runs ok again, not great because my old sensor has a low voltage reading but atleast it will stay running and not stumble, although fuel mileage sucks. I sent a message to rock auto informing them that the new sensor was bad and requested a new one. By the way it was acting and the readings I was getting from it, I suspect there was a short in the new sensor.

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If it were quick and easy everyone would be doing it!