P0420 Fault on 2001 Chevrolet Cavalier 2.2L - Diagnosis and Next Steps
Hi, I own a 2001 Chevrolet Cavalier with a 2.2L engine, automatic transmission, and currently at 109,000 miles. A few months ago, I experienced a random misfire (likely P0300) accompanied by rough idle and stalling at stops. After replacing the fuel filter, fuel pump, air filter, spark plugs, ignition wires, and performing a Seafoam treatment at the throttle body, the issue was resolved with the replacement of the ignition coils. Shortly after that, the check engine light activated with a P0420 code. The vehicle runs smoothly, has excellent fuel efficiency, and shows no exhaust rattling or foul odors. I recently drove it from Florida to Massachusetts without any issues. So far, I've only verified the throttle body seal is intact. What should I check next to diagnose and resolve the P0420 code? Is there a specific component or system that needs further inspection?
Repeated misfires can degrade the catalytic converter over time. The P0420 code typically indicates insufficient exhaust gas conversion, which may point to a failing catalyst. A replacement of the catalytic converter is likely needed in this case.