Catalyst System Efficiency
Diagnostic Codes: P 0420, P 0430HO2S Characteristic:
Monitoring Procedure
The condition of the catalyst is determined using the difference between the signals from the upstream and down-stream oxygen sensors, and the time taken to switch from rich to lean vehicle conditions are checked for optimum conditions both before and during monitoring so that a steady state exists for successful catalyst monitoring to be achieved.
The strategy will report to the Diagnostic Status Manager (DSM) when a catalyst monitoring fault is present and the DSM will then decide whether to store a fault code and illuminate the MIL Lamp.
Catalyst Efficiency
Catalyst Efficiency Low - Bank 1, P 0420
Catalyst Efficiency Low - Bank 2, P 0430
Possible Causes:
- Catalyst fault - poor oxygen storage A,B
- Severe exhaust air leak A,B
- Slow response upstream oxygen sensor A,B
- Additional capacitance (upstream oxygen sensor) - harness fault A,B
- ECM filter wrong - oxygen sensor A,B
- Wrong load/Speed sites - inlet air leak or air meter fault