Stupid question really, but I can't find the answer by searching. I replaced an o2 sensor that was supposed to be bad. I have to get my car emission tested (Ohio eCheck) tomorrow morning early because my plates expired. They won't even test your car if the CEL is on. I wanted to make sure the new sensor is working properly before I take it off the jack stands. How long should it take for the CEL to come back on if the ECU is reset? I let it run for like 10 minutes and it got up to 145* and no CEL. If the sensor wasn't reading right would it come on within 10 minutes?

 

it'll take a while.. take it to Autozone or somethin like that, have em read the code, an tell em to clear it while they're out there

 

I think it's something like 40 car restarts before it'll eventually reset. Best bet, stop at auto zone or something before here.

 

how did you reset your ECU? if you take your negative battery terminal off for 15 minutes it resets the ECU, if the code doesn't come back you should be good. if it does you didn't fix the problem.

 

Well yeah that's the general idea lol. I left the cable off overnight so it reset. My concern was that I didn't know which o2 was actually bad. I replaced the one on the manifold, let it idle for 10 minutes and no code... YET. I'm going to keep my fingers, toes and nipples crossed until tomorrow morning that this stupid CEL doesn't come on before I get through eCheck. Otherwise I'll have a nice fine to pay! I would think it may take 15-20 miles before it would come back on.