i have a problem with upstream o2 sensor heater codes. have replaced sensors, ecm, and wiring all checks out perfectly. have power through fuse, relay, and sensors. also have good wires from sensors back to ecm. that's the entire circuit. any ideas!!!

 

What are the specific codes?? Or what year make and model?? If you are getting a code for low voltage to the o2 sensor and also getting codes for a lean mixture, it could have nothing to do with the o2 sesor itself, and could be another problem like a MAF sensor failing.

 

You can, If you get a DTC for a o2 sensor having low or high voltage, that doesnt mean that the sensor is bad, it means there is something causing the sensor to have low or high voltage. Low voltage means the exhaust is to lean, and high voltage means the exhaust is to rich. Anything that can cause the o2 sensor to go to high or low in voltage will trip the light. Its a B code, so it would take to trips for the light to come on. I need to know what the actual codes are though, the are manufacter specified codes but I wanna be sure.