Chevrolet Repair Questions? Ask a Mechanic for Answers ASAP
Does the vehicle have an aftermarket remote start system?
I'm looking up diagrams for any common circuits that might cause all o2 sensors to set like that.
Aftermarket electronics will sometimes interfere with the O2 sensor heater circuit, but if it's all stock then I'll have to do some research to see what it could be.
You replaced all O2 sensors with GM parts?
Do you have a scan tool to monitor O2 sensor data?
If so, try the following:
Allow the engine to cool for a hour. Do NOT turn the key on. Connect and set up a scanner. Locate and monitor the HO2S B1S2 and B2S2. Then turn the key on, engine off. Monitor the amperage value. If the amperage displayed exceeds 1.375 amps, replace the O2 sensor/s.
Sorry. I got stuck in traffic on the way home. You can respond at your convenience, don't worry about the chat ending or anything.
If the sensors are all in range then there has to be some kind of wiring issue that intermittently interferes with communication with the pcm. I'll look up some diagrams of the pcm so we can trace each circuit. Do you have multi meter?