Hey, mabe my problem is a broken O2 wire. How would I test this? I have changed both o2's and both o2 sims and I am still getting a reading of 8mv for one of the o2's.

 

Anyone know how to check for a broken wire inside a wiring harness?

 

Which sensor reads 8mV (Bank ?/Sensor ?)?

What does the sensor read on cold start? 450mV?.... or does it ALWAYS show 8mV?

If you swap sensors, left to right, does the problem follow the sensor, or stay on the same side? If it stays on the same side, its a wiring problem.

Unplug the harness. Have you checked the "heater" circuits? Do you have +12V on the harness brown wire? Do you have a good ground on the harness black wire? Do you get 0V on the harness tan wire?

 

Injuneer,

Is that all that is involved to test the heater circuits, what you just posted? Do you do this with the key in th eon position or do you have to start the car to get those readings?

Thanks

Jason

 

The heaters get +12V (brown wire on harness, pink wire on sensor) from the same fuse as the EGR solenoid, EEC solenoid, Reverse lockout and skip shift solenoids. These are "switched".... you have to turn the key on for the power to be at the harness connector. The ground is always there.

 

Thanks Injuneer

Jason

 

Yes, cold or hot it always reads 8mv. I figured it was a wiring problem. What is a heater circuit? Do you mean unplug the wiring harness from the O2 sensor or the PCM? I might be emailing you Injuneer.

 

Fred? Anyone else.

 

All the O2 sensors from 94 and up are 4-wire "heated" sensors. There are two wires that use +12V (brown) and a ground (black) to heat the O2 sensor up. If they aren't hot, they won't work, although just the heat of the exhaust is often enough to keep them warm enough. The other two wires are for the O2 signal to the PCM. It sounds like you have a short or a bad connection on the purple (harness) wire or purple/white (other side).

Unplug the harness connector from the O2 sensor connector and see if you have +12V to the harness brown wire. That is not likely the problem if the sensor always reads .008V. That would indicate the sensor is shorted to ground, or the wire isn't connected at all. But usually, the dead or "cold" sensor will just read 450mV, reflecting the voltage the PCM applies.