guys, i am having a problem with my right side o2 sensor. with KOEO left side is .450V and right side spikes to 1.092V. in the factory service manual there is a procedure to test the wiring at the 02 connector for the 2 wires that go to the pcm and it checks out good. if i take the sensor out of the bung (not grounded) the voltage goes to .450v. i can ground the threads of the sensor to frame (not in the bung) and the voltage spikes back to 1.093v. with the engine running it is the same thing. i have inspected the wiring, put a known good sensor in and the same thing happens. any suggestions?

 

There are 4 wires in the harness. There's a 12V wire and a ground for the heater in the sensor. There's a signal wire and a ground for the sensor itself. Whether its grounded to the bung shouldn't make any difference.

450V is the signal you will get from a cold sensor, or an open circuit (the PCM supplies the 0.450V reference voltage). Sounds like there may be a voltage leakage between the signal wire and the heater wires.

 

well let me tell you about that voltage leak. not proud to say it but my troubleshooting only consisted of swapping out o2 sensors and visually inspecting the wiring harness for burns. you see, i have longtubes, and with longtubes comes o2 harness extentions. i finally plugged the o2 sensor straight into the stock harness (and grounded the sensor) and it worked like it should. so i unwrapped the tape on the extention wiring to find an sharp edge on the pcm signal wire solder joint that worked its way through 2 layers of shrinkwrap tubing into the heater circuit ground wire. heat+over tightly wrapped wires+sharp edges= voltage leak....

another thing that i found that may be worth passing on...
with the o2 sensor completely out of the car, there is continuity between the threads of the o2 sensor and the tan wire(pcm lo input). for me, without the threads grounded the o2 it only read reference voltage. i checked this with 3 different o2 sensors and found the same thing with each. thanks for your help! now i just gotta get rid of that 5k+ rpm stumble....