96 Maxima - 0503 and 0303 O2 sensors

I keep getting these codes: P0150 and P0130 or 0303 and 0503 codes for my O2 sensors on my 96 Maxima. Here is how it began: I would get a misfire every now and then, mainly at idle while with trans in drive, stopped. Every now and then, it would miss in the lower rpm's under acceleration, but it remained mostly confined to idle speed around

625rpm. I checked ALL rubber and steel vacuum lines, EGR & MAP solenoids, and some others I do not know the name of with my vacuum tester, all check fine. Eventually, the misfire got a little worse. It took 8 months for the engine to start misfiring consistently and long enough to get out of the car then under the hood to start unplugging coils and injectors to isolate the #6 cylinder as the culprit before the misfire would disappear. I never thought I would be so happy to have a part fail!! I test swapped the coil pack with #4 and the misfire followed the coil. $80 later, a new coil pack cured my mysterious and elusive misfire. The damned PCM NEVER did record a single misfire...

In the midst of trying to find my bad coil, I decided to clean or "Tune Up" my electrical connections under the hood, hoping this would help eliminate or isolate some of my problems. I cleaned EVERY connector under the hood with tech grade contact cleaner. After doing so, I came up with these O2 sensor error codes. I reset the PCM and re- cleaned the O2 sensor connections, ensuring a fully seated connection but again the codes came back. According to the Haynes manual, I should see actively switching voltage from 0.1 through 0.9 volts on the white wire when the sensors are up to operating temp. I backprobed the O2 sensors and observed the voltage switching high and low as I opened and closed the throttle, but it was in the (-)VDC (I use a FLUKE 179 DMM). I think the manual is saying there should be (+) voltage here but it does not specify polarity, just neg lead to gnd and pos to white wire. It strikes me as odd that I read this (-) voltage, but the sensors do switch actively while running.... They are also getting 12V for the O2 heaters...

What really puzzles me is how BOTH upstream O2 sensors failed at the same time. Did this connector "Tune Up" fry my O2 sensors?

There is no question of cleanliness in my connections, and no wiring problems present. In fact, the wiring is in excellent condition.

Is it possible I have another sensor failing elsewhere causing these codes? Bad or contaminated go juice? Leaking Injectors? or, have I fried my O2's or my PCM?!?!?

Please Help!!!

-Adam

Reply to
adupyours
Loading thread data ...

MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.