DTC P0420: Left Bank Catalyst System Low Efficiency, Or DTC P0430: Right Bank Catalyst System Low Efficiency: Condition

DTC is set when value from HO2S No. 2 becomes closer to value from HO2S No. 1 at either bank. MIL is illuminated when Power Control Module (PCM) detects malfunction during 2 consecutive drive cycles. Possible causes are:

• Catalytic converter malfunction.
• Exhaust system leak.
• HO2S No. 2 malfunction.
• PCM malfunction.