DrivenWS6

iTrader: (1)

I was just wondering if the PCM monitors the rear O2 sensors continously or it just does like a check every so often or so long. The reason I am asking this is because my car is throwing the catalyst efficiency code but if i clear the codes the light will stay off for prolly a couple weeks or 500 miles or so and come back on and I have noticed it only comes when im idling. If im cruising down the road or driving it wont come on but I can pull up to a stoplight and just like that it will come on. So I guess im trying to figure out if its the cats getting lazy or the O2. So that is where my question comes in about how or when the PCM monitors the rear O2's.

And also if I were to take it do a dealer to have the car replaced under 80k mile warranty will they just replace it if I ask them to or will they do there own diagnosis on it. I dont have the money for a big bill from GM right now so i dont want to take it there and end up having a bill for all these tests and crap they run and tell me it wasnt the cats. Anyways sorry for dragging this on so long and any help would be great, Thanx Ben

joshp14

iTrader: (5)

What code(s) are you getting? If you are getting like a P0420 or P0430, then its more than likely a cat. A good way to find out is swap the rear O2's....if the problem follows the O2, then its the O2. If the problem stays with the cat, then its the cat.

DrivenWS6

iTrader: (1)

Yeah I think its a PO420. Im not positive because I dont have a scan tool with me. It was something like catalyst efficiency below threshold on the left side.

And by the way I see that your a GM tech, do they make a big deal about it if you bring it in and want the cat changed or are they usually pretty good about it?

joshp14

iTrader: (5)

Yea its a cat. Take it to the dealer and they should replace it free if under 80k. I have done sevral of the drivers side cats on the f-bods, it seems GM had a bad batch of them or something. More of the 01-02 cars go bad than the older ones.