DTC    P0420    Catalyst System Efficiency Below Threshold (Bank 1)

MONITOR DESCRIPTION

CATALYST LOCATION

MONITOR STRATEGY

TYPICAL ENABLING CONDITIONS

CONFIRMATION DRIVING PATTERN

CONDITIONING FOR SENSOR TESTING

INSPECTION PROCEDURE

CHECK ANY OTHER DTCS OUTPUT (IN ADDITION TO DTC P0420)

PERFORM ACTIVE TEST USING INTELLIGENT TESTER (CONTROL THE INJECTION VOLUME)

CHECK FOR EXHAUST GAS LEAK

PERFORM ACTIVE TEST USING INTELLIGENT TESTER (CONTROL THE EGR STEP POSITION)

INSPECT EGR VALVE ASSEMBLY

REPLACE FRONT EXHAUST PIPE ASSEMBLY (TWC: FRONT AND REAR CATALYST)

REPLACE AIR FUEL RATIO SENSOR (SENSOR 1)

CHECK FOR EXHAUST GAS LEAK

REPLACE HEATED OXYGEN SENSOR (SENSOR 2)

INSPECT FOR EXHAUST GAS LEAK

PERFORM ACTIVE TEST USING INTELLIGENT TESTER (CONTROL THE EGR STEP POSITION)

INSPECT EGR VALVE ASSEMBLY

CHECK ENGINE TO DETERMINE CAUSE OF EXTREMELY RICH OR LEAN ACTUAL AIR FUEL RATIO

CHECK WHETHER DTC OUTPUT RECURS

REPLACE FRONT EXHAUST PIPE ASSEMBLY (TWC: FRONT AND REAR CATALYST)