Technical Definition:

Main Catalyst Efficiency Below Threshold (Bank 1)

Technical Description:

Possible Causes:

Possible Symptoms:

Main Catalyst Efficiency Below Threshold Bank 1

Possible Solutions:

OBD-II Trouble Code Type:

Diagnostic Step:

Tech Notes:

– Warm Up Three Way Catalytic converter deterioration or malfunction
– Exhaust system leaks
– Loose front or rear HO2Ss
– Faulty front heater O2 sensor
– O2 sensors harness is open or shorted
– O2 sensors poor electrical connection

Specific Makes: