2002 Monte Carlo - p0420 code

My daily is a 2002 Monte Carlo SS with the N.A. 3800 V6. Car currently has 96,000 miles and is not modified. At 93,000 miles the catalytic converter front nosecone broke off and car had drivability issues. Local mechanic replaced the catalytic converter and all was well until now (~2000 miles later). (Car feels brand new!)

Car has P0420 (low catalyst function) code. I reset once and it returned 500 miles later. It shouldn't be the converter, so I thinking downstream O2 sensor?


Also, anyone know where the trunk release relay is located?

My daily is a 2002 Monte Carlo SS with the N.A. 3800 V6. Car currently has 96,000 miles and is not modified. At 93,000 miles the catalytic converter front nosecone broke off and car had drivability issues. Local mechanic replaced the catalytic converter and all was well until now (~2000 miles later). (Car feels brand new!)

Car has P0420 (low catalyst function) code. I reset once and it returned 500 miles later. It shouldn't be the converter, so I thinking downstream O2 sensor?
Also, anyone know where the trunk release relay is located?


IT is possible that the cat converter is defective. also the O2 sensor may have been damaged when the converter was replaced.

I would replace the upstream and down stream O2 sensors since they are at 100,ooo mi. make sure the wires and connectors are OEM no hacked and sliced as this is why they do cause false signals.