PO420 Fault Code on 2002 Chevrolet Avalanche - Catalyst System Efficiency Below Threshold (Bank 1)

Model: 02 Avalanche Fault Code: P0420 Posted: 2006-11-08 17:18

I have a 2002 Chevrolet Avalanche that is triggering a PO420 diagnostic code, indicating catalyst system efficiency below threshold for Bank 1. The issue is related to the oxygen sensor in the exhaust system detecting poor catalytic converter performance. Should I replace the catalytic converter or simply clean the EGR valve? What is the recommended troubleshooting approach to resolve this issue effectively? Ron