Thread: Replacing O2 sensors

Thanks everyone. I think I'll pick up a scanner and go from there. At least if it is the O2 sensor I'll know to replace only the one on the rear manifold. I'm assuming that AC Delco is the most suitable brand of sensor for the Grand Prix. I've heard bad things about the Bosch ones ...

You would know if its the upper manifiold O2 if your MPG has been continuing to drop since the light came on.

The rear O2, although IMO usless, acts as a warning system and will still set a check engine light (Code P240)... and cause you to fail inspection in most citys/states

Find out which one it is an replace it... if you have a 00-03 then you can buy a o2 simulator for the rear one... its a little cheaper and if you ever get a downpipe then you have already gotten rid of the code that it will throw

Also... your are correct about the AC delco thing... go with the OEM... the bosch's are crap for most GM applications