O2 sensor failures do not set CEL's, why would it? it has no control over what the car does, the computer doesn't know its not working, it thinks the motor is messed up not the O2 sensor. when an O2 sensor fails the ecu read it as the engine is running lean, so it adds more fuel, over time this will change the fuel trim for the vehicle and eventually set a CEL for a lean engine, but the length of time needed to do that is not the same for all cars so i couldn't tell youModemagic said:Already tried the 'unplug and see' trick. I suspect my o2 sensor is trashed, but the ecu throws no codes, even if I unplug it. I think my car does run rich, I smell an abundance of fuel while it runs in the motor area. It never tripped the CE light, so I dunno if its supposed to and didn't, making me wonder if my ECU is jackked or what.
your ecu is fine, the only way to test an O2 sensor on an OBD1 car is with a digital multimeter and a t-pin, stick the t-pin into the signal wire of the O2 sensor (idk which one it is one your car, if its a 3 wire connector, slide the t-pin into the connector next to the wire, then attach the multimeter and with the car running check the voltage (set the meter to read DC voltage on a scale of 0-1v, if its working properly it should go below 200mV, and aboce 800mV
the temperature if the cylinder has ablsoultly nothing to do with the reading, that just choose to put the sensor there, and there isn't a rich or lean cylinder, they all change from rich ot leanvelardejose said:Maybe it's the hottest or leanest?
In our beloved vw bugs n°4 was the hottest because it was offset from the cooling air flow...