DTC P0421:00 [MZR 1.6]

id0102h3704400

DTC P0421:00

Warm up catalyst system efficiency below threshold
DETECTION CONDITION
•  The PCM compares the number of A/F sensor and HO2S inversions for a predetermined time. The PCM monitors the HO2S inversion counts when the following conditions are met. The PCM detects inversion ratio. If the inversion ratio is below specification, the PCM determine that catalyst system has deteriorated.
MONITORING CONDITION
―  Catalyst converter temperature: more than 400 °C {752 °F}
―  Engine speed: 1,500—3,500 rpm
―  LOAD: 20—50% (at engine speed 2,000 rpm)
Diagnostic support note
•  This is an intermittent monitor (catalyst).
•  The check engine light 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 (Mode 2)/Snapshot data is available.
•  DTC is stored in the PCM memory.
POSSIBLE CAUSE
•  Leakage exhaust system
•  A/F sensor looseness
•  HO2S looseness
•  TWC malfunction
•  PCM malfunction

Diagnostic Procedure

STEP

INSPECTION

ACTION
1
VERIFY FREEZE FRAME DATA (MODE 2)/SNAPSHOT DATA AND DIAGNOSTIC MONITORING TEST RESULTS HAVE BEEN RECORDED
•  Have the FREEZE FRAME DATA (Mode 2)/snapshot data and DIAGNOSTIC MONITORING TEST RESULTS (catalyst related) been recorded?
Yes
Go to the next step.
No
Record the FREEZE FRAME DATA (Mode 2)/snapshot data and DIAGNOSTIC MONITORING TEST RESULTS on 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 Service Information.
•  If the vehicle is not repaired, go to the next step.
No
Go to the next step.
3
VERIFY RELATED PENDING CODE AND STORED DTC
•  Switch the ignition off, then ON (engine off).
•  Verify the related PENDING CODE and stored DTCs using the M-MDS.
•  Are any other DTCs present?
Yes
Go to the applicable DTC inspection.
(See DTC TABLE [MZR 1.6].)
No
Go to the next step.
4
INSPECT GAS LEAKAGE FROM EXHAUST SYSTEM
•  Visually inspect exhaust gas leakage in the exhaust system.
•  Is there any leakage?
Yes
Repair or replace the malfunctioning part according to the inspection results, then go to Step 8.
No
Go to the next step.
5
INSPECT INSTALLATION OF A/F SENSOR
•  Inspect if the A/F sensor is loosely installed.
•  Is the A/F sensor installed securely?
Yes
Go to the next step.
No
Retighten the A/F sensor, then go to Step 8.
(See AIR FUEL RATIO (A/F) SENSOR REMOVAL/INSTALLATION [MZR 1.6].)
6
INSPECT INSTALLATION OF HO2S
•  Inspect if the HO2S is loosely installed.
•  Is the HO2S installed securely?
Yes
Go to the next step.
No
Retighten the HO2S, then go to Step 8.
(See HEATED OXYGEN SENSOR (HO2S) REMOVAL/INSTALLATION [MZR 1.6].)
7
INSPECT TWC
•  Clear the DTC from the PCM memory using the M-MDS.
•  Switch the ignition off, then ON.
•  Inspect the TWC.
•  Is there any malfunction?
Yes
Replace the TWC, then go to the next step.
(See EXHAUST SYSTEM REMOVAL/INSTALLATION [MZR 1.6].)
No
Go to the next step.
8
VERIFY DTC TROUBLESHOOTING COMPLETED
•  Always reconnect all disconnected connectors.
•  Switch the ignition ON (engine off).
•  Clear the DTC from the PCM memory using the M-MDS.
•  Perform the Drive Mode 01 (PCM Adaptive Memory Produce Drive Mode).
•  Is the PENDING CODE for this DTC present?
Yes
Repeat the inspection from Step 1.
•  If the malfunction recurs, replace the PCM.
Go to the next step.
No
Go to the next step.
9
VERIFY AFTER REPAIR PROCEDURE
•  Perform the “AFTER REPAIR PROCEDURE”.
•  Are any DTCs present?
Yes
Go to the applicable DTC inspection.
(See DTC TABLE [MZR 1.6].)
No
DTC troubleshooting completed.