DTC P0421:00 [L5]


id0102c9704400

DTC P0421:00

Warm up catalyst system efficiency below threshold

DETECTION CONDITION
•  The PCM monitors the input voltage from the middle A/F sensor and the HO2S output current when the following conditions are met. If the input voltage change is extremely large compared to the output current change, the PCM determines that the catalyst system has deteriorated.
MONITORING CONDITION
―  ECT: more than 70 °C {158 °F}
―  Catalyst converter temperature: more than 350 °C {662 °F}
―  Engine speed: 1,000— 4,000 rpm
―  LOAD: 19— 56% (at engine speed 2,000 rpm)
―  Time with purge control system does not operate: more than 5 s
Diagnostic support note
•  This is an intermittent monitor (Catalyst).
•  MIL illuminates if PCM detects above malfunction condition in two consecutive drive cycles or in one drive cycle while DTC for the same malfunction has been stored in PCM.
•  PENDING CODE is available if PCM detects the above malfunction condition during first drive cycle.
•  FREEZE FRAME DATA is available.
•  The DTC is stored in the PCM memory.
POSSIBLE CAUSE
•  Exhaust gas leakage
•  Loose A/F sensor
•  Loose HO2S
•  TWC deterioration or malfunction
•  PCM malfunction

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.
No
Record the FREEZE FRAME DATA and DIAGNOSTIC MONITORING TEST RESULTS on the repair order, then go to the next step.
2
VERIFY RELATED SERVICE INFORMATION AVAILABILITY
•  Verify related Service Information availability.
•  Is any related Service Information available?
Yes
Perform repair or diagnosis according to the available repair information.
•  If the vehicle is not repaired, go to the next step.
No
Go to the next step.
3
VERIFY RELATED PENDING CODE OR STORED DTC
•  Switch the ignition to off, then to the ON (Engine off).
•  Verify the related PENDING CODE or stored DTCs.
•  Are other DTCs present?
Yes
Go to the applicable DTC inspection.
No
Go to the next step.
4
INSPECT EXHAUST SYSTEM FOR EXHAUST GAS LEAKAGE
•  Visually inspect exhaust gas leakage in the exhaust system.
•  Is there exhaust gas leakage?
Yes
Repair or replace the malfunctioning part, then go to Step 7.
No
Go to the next step.
5
INSPECT INSTALLATION OF HO2S
•  Inspect the HO2S for looseness.
•  Is it normal?
Yes
Go to the next step.
No
Retighten the HO2S, then go to Step 7.
6
INSPECT TWC
•  Clear the DTC using the M‐MDS generic OBD function.
•  Switch the ignition to off then back to the ON.
•  Inspect the TWC.
•  Is it normal?
Yes
Go to the next step.
No
Replace the TWC, then go to the next step.
7
VERIFY TROUBLESHOOTING OF DTC P0421:00 COMPLETED
•  Make sure to reconnect all disconnected connectors.
•  Switch the ignition to ON (Engine off).
•  Clear the DTC from the memory using the M‐MDS.
•  Perform the A/F sensor heater, HO2S heater, A/F sensor, HO2S, and TWC Repair Verification Drive Mode.
•  Is the PENDING CODE for this DTC present?
Yes
Replace the PCM, then go to the next step.
No
Go to the next step.
8
VERIFY AFTER REPAIR PROCEDURE
•  Perform the “AFTER REPAIR PROCEDURE”.
•  Are any DTC present?
Yes
Go to the applicable DTC troubleshooting.
No
Troubleshooting completed.