CUSTOMER CONCERN The check engine light is on with catalyst-efficiency DTC P0420 after induction-system service. CAUSE Fuel-control, oxygen-sensor, and converter testing confirmed that the catalytic converter was no longer operating efficiently. CORRECTION Remove and replace the failed catalytic converter.

CUSTOMER CONCERN The check engine light is on with catalyst-efficiency DTC P0420 stored. CAUSE Fuel-trim, exhaust-leak, and oxygen-sensor checks confirmed that the catalytic converter was no longer operating efficiently. CORRECTION Remove and replace the catalytic converter.

CUSTOMER CONCERN Customer states the check-engine light is on. DTC P0420 is stored. CAUSE Exhaust-manifold, misfire, coolant-consumption and fuel-trim checks confirmed the catalytic converter was below efficiency. CORRECTION Remove and replace catalytic converter. Clear DTC P0420 and verify catalyst-monitor operation.