Car Questions

Clear all

2002 Blazer 155K o2 and Cat monitors not setting, no error codes


Topic starter

I have been doing some research and not sure what to next. My OBD scan tool shows activity on all 3 o2 sensors. I did change the downstream o2 sensor(after the cat) because of a heating element error code and replaced it with a OEM part about a year ago. I have heard that maybe the Cat could be bad or maybe that my gas gauge fluctuates ( goes from full to empty regardless of how much gas is in the tank, sometime whips back and forth while driving) that may cause the ECM to not let the monitors to set. According to the book it expects 1/4 to 3/4 in tank. Before I start changing anything else I though you might have a though on what to do next. 

Thank You and I appreciate any advice you might have.

Ron Russo

West Babylon NY     

1 Answer

Well for my experience, when they do that it's usually the catalytic converter itself. But that's if the wiring hasn't been damaged. If the wiring's been damaged anywhere from the oxygen sensor to the computer wiring, then all bets are off

Scotty if the sensor shows activity would that indicate the wiring is not damaged ? if not is there any particular place the wiring would be damaged and whats the best way to check