dtc error code po420

[vinniedee]

dtc error code po420, catalyst effiency below threshold, bank 1.

anyone have any ideas?
Vinnie

[BNaylor]

Normally it means your CAT convertor is bad. Sometimes a flaky rear 02 sensor can cause it but I doubt it.

Since you have a 2001 model GP contact Pontiac Customer Service or the local Pontiac dealer and give them the VIN number because you may qualify for a free CAT convertor. The warranty on the CAT for certain 2001 - 2002 models was extended to 10 years or 120K miles, whichever comes first. It covered ones both the 3.1L and 3.8L engines.

[maxwedge]

This can be a complicated diagnosis, p0420 is a comparison of the pre cat sensor and the post cat sensor and how the pcm interpets these inputs, there are several comprehensive tech articles on this, you could google that code or check batauto.com and do a search for that code much has been discussed. Or do what Bnaylor says, didn't see his post, but the info is out there for the diagnostic issue in question.