Diagnostic procedure

DTC P0421 - DIAGNOSTIC PROCEDURE

STEP	INSPECTION		ACTION
1	VERIFY FREEZE FRAME DATA AND DIAGNOSTIC MONITORING TEST RESULTS HAVE BEEN RECORDED Have FREEZE FRAME DATA and DIAGNOSTIC MONITORING TEST RESULTS (Catalyst related) been recorded?	Yes	Go to the next step.
1		No	Record FREEZE FRAME DATA and DIAGNOSTIC MONITORING TEST RESULTS on repair order, then go to the next step.
2	VERIFY RELATED REPAIR INFORMATION AVAILABILITY Check for related Service Bulletins and/or on-line repair information availability. Is any related repair information available?	Yes	Perform repair or diagnosis according to the available repair information. If the vehicle is not repaired, go to the next step.
2		No	Go to the next step.
3	VERIFY RELATED PENDING CODE OR STORED DTCS Turn key to OFF then ON (Engine off). Verify related pending code or stored DTCs. Is other DTCs present?	Yes	Go to appropriate DTC troubleshooting.
3		No	Go to the next step.
4	INSPECT GAS LEAKAGE OF EXHAUST SYSTEM Visually inspect exhaust gas leakage in exhaust system. Is there gas leakage?	Yes	Repair or replace faulty exhaust parts, then go to Step 8.
4		No	Go to the next step.
5	INSPECT INSTALLATION OF FRONT AND REAR OXYGEN SENSORS Inspect for looseness of front and rear oxygen sensors. Is it normal?	Yes	Go to the next step.
5		No	Retighten sensor, then go to Step 8.
6	INSPECT FRONT HO2S VOLTAGE Access O2S11 for P0421 or O2S21 for P0431 PID using the WDS or equivalent. Verify PID while racing engine (in PARK or NEUTRAL). Is PID reading okay? More than 0.45 V when suddenly depress accelerator pedal (rich condition). Less than 0.45 V just after release accelerator pedal (lean condition)	Yes	Replace WU-TWC, then go to the next step.
6		No	Replace suspected sensor, then go to the next step.
7	VERIFY TROUBLESHOOTING OF DTC P0421 OR P0431 COMPLETED Make sure to reconnect all disconnected connectors. Turn key to ON (Engine off). Clear the DTC from the memory using the WDS or equivalent. Start engine and perform DRIVE MODE except for DRIVE MODE 4. (See OBD-II DRIVE MODE .) Is PENDING CODE for this DTC present?	Yes	Replace PCM, then go to the next step.
7		No	Go to the next step.
8	VERIFY AFTER REPAIR PROCEDURE Perform the "After Repair Procedure". (See AFTER REPAIR PROCEDURE .) Are any DTCs present?	Yes	Go to the applicable DTC inspection. (See DTC TABLE .)
8		No	Troubleshooting completed.