P0420 Fault in 2003 Chevrolet Suburban 5.3L: Diagnosis and Solutions
My check engine light activated, so I took the vehicle to AutoZome to retrieve diagnostic codes. The system displayed a repair recommendation for ECM wiring and identified code P0420. I replaced both oxygen sensors on Bank One. After the replacement, the check engine light turned off for one day before returning. Despite this, the issue persists. What could be causing this? Are there any underlying problems that might be contributing to the P0420 fault?
The message 'repair ECM wiring' is confusing — if the vehicle is communicating normally and no other error codes are present, why would there be a concern about ECM wiring?\n\nWhy were both O2 sensors on Bank One replaced?\n\nCatalytic converter failures (like P0420) often stem from unaddressed issues such as running rich, head gasket leaks, or misfires (e.g., P030x codes). Did the vehicle have any prior trouble codes or performance issues?\n\nA scanner with live data is essential to properly diagnose the root cause.\n\nTip: Is this a stock 2003 Chevrolet Suburban 5.3L, or has it been modified in any way?