DTC P0421:00 [SKYACTIV-G 2.0, SKYACTIV-G 2.5]

id0102h4704400

SKYACTIV-G 2.0 (MTX)

DTC P0421:00	Warm up catalyst system efficiency below threshold
DETECTION CONDITION	•  The PCM compares the number of the A/F sensor and HO2S inversions for a predetermined time to detect the inversion ratio. It does this by monitoring the HO2S inversion counts when the following conditions are met. If the inversion ratio is below specification, the PCM determine that the catalyst system has deteriorated. ―  The A/F sensor inversion counts is as prescribed when the following monitoring conditions are met: ―  The accumulated occurrence time of the following monitoring conditions has exceeded the prescribed time limit: MONITORING CONDITIONS •  Calculated WU-TWC temperature: above 400 °C {752 °F} •  Engine speed: 1,100—3,000 rpm •  LOAD: 15—50 % (at engine speed of 2,000 rpm) Diagnostic support note •  This is an intermittent monitor (catalyst). •  The check engine light illuminates if the PCM detects the above malfunction condition in two consecutive drive cycles or in one drive cycle while the DTC for the same malfunction has been stored in the PCM. •  PENDING CODE is available if the 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.
FAIL-SAFE FUNCTION	Not applicable
POSSIBLE CAUSE	•  Exhaust system leakage •  A/F sensor loose •  HO2S loose •  WU-TWC deterioration or malfunction •  PCM malfunction
SYSTEM WIRING DIAGRAM	Not applicable

Diagnostic Procedure

SKYACTIV-G 2.0 (ATX), SKYACTIV-G 2.5

Note

•  To determine the malfunctioning part, proceed with the diagnostics from "Function Inspection Using M-MDS".

Details On DTCs

DESCRIPTION	Catalytic converter system
DETECTION CONDITION	Determination conditions	•  The PCM detects that the HO2S output fluctuates from lean to rich in a short amount of time at specified times continuously after recovery from fuel cut control.
	Preconditions	•  Catalytic converter (WU-TWC) is activated sufficiently. •  HO2S is activated sufficiently. •  The following DTCs are not detected: ―  Misfire: P0300:00, P0301:00, P0302:00, P0303:00, P0304:00 ―  Fuel injection correction: P0171:00, P0172:00, P2096:00, P2097:00 ―  A/F sensor: P0130:00, P0131:00, P0132:00, P0133:00, P0134:00, P064D:00, P2237:00, P2243:00, P2251:00 ―  HO2S: P0137:00, P0138:00, P013A:00, P0140:00 ―  A/F sensor heater: P0031:00, P0032:00 ―  HO2S heater: P0037:00, P0038:00
	Drive cycle	•  2
	Self test type	•  CMDTC self test
	Sensor used	•  A/F sensor, HO2S
FAIL-SAFE FUNCTION	•  Not applicable
VEHICLE STATUS WHEN DTCs ARE OUTPUT	•  Illuminates check engine light.
POSSIBLE CAUSE	•  HO2S malfunction ―  HO2S loose •  A/F sensor malfunction ―  A/F sensor loose ―  Exhaust system leakage ―  A/F sensor deterioration •  WU-TWC deterioration or malfunction •  PCM malfunction

System Wiring Diagram

•  Not applicable

Function Explanation (DTC Detection Outline)

•  The PCM monitors the oxygen storage amount proportional to the catalytic converter purification characteristic.

•  The PCM starts to monitor after recovery (fuel injection starts) from fuel cut control.

•  The PCM temporarily changes the target air/fuel ratio to rich at fuel cut recovery, and detects the response time until the rear HO2S output signal outputs the voltage on the rich side.

•  If the catalytic converter purification characteristic deteriorates, the amount of the time until the rear HO2S detects the voltage on the rich side is shorter compared to the normal purification characteristic. (refer to the following figure)

The PCM detects a catalytic converter malfunction using this characteristic.

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Repeatability Verification Procedure

1.  Start the engine and leave it idling for 1 min.

2.  Drive the vehicle normally for 15 min. After that, shift to 3rd gear and maintain the vehicle speed at approx. 40 km/h {25 mph}.

3.  Accelerate the vehicle to 60 km/h {37 mph} while in 3rd gear.

4.  Release the accelerator pedal and decelerate the vehicle to 40 km/h {25 mph}.

5.  Accelerate the vehicle to 60 km/h {37 mph} again while in 3rd gear.

6.  Drive the vehicle for 20 s at a speed of 50 km/h {31 mph} while in 3rd gear.

7.  Repeat Step 4 to 6 operations above 20 times.

Note

•  Match the engine coolant temperature in the recorded FREEZE FRAME DATA (Mode 2)/snapshot data, the vehicle speed, and engine speed values to the best extent possible while driving the vehicle.

8.  Try to reproduce the malfunction by driving the vehicle for 5 min based on the values in the FREEZE FRAME DATA (Mode 2)/snapshot data.

PID Item/Simulation Item Used In Diagnosis

PID/DATA monitor item table

Function Inspection Using M-MDS

STEP	INSPECTION	RESULTS	ACTION
1	PURPOSE: 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.
2	PURPOSE: IDENTIFY TRIGGER DTC FOR FREEZE FRAME DATA (MODE 2) •  Is the DTC P0421:00 on FREEZE FRAME DATA (Mode 2)?	Yes	Go to the next step.
		No	Go to the troubleshooting procedure for DTC on FREEZE FRAME DATA (Mode 2). (See DTC TABLE [SKYACTIV-G 2.0, SKYACTIV-G 2.5].)
3	PURPOSE: RECORD VEHICLE STATUS AT TIME OF DTC DETECTION TO UTILIZE WITH REPEATABILITY VERIFICATION •  Has the FREEZE FRAME DATA (Mode 2)/snapshot data been recorded?	Yes	Go to the next step.
		No	Record the FREEZE FRAME DATA (Mode 2)/snapshot data on the repair order, then go to the next step. Note •  Recording can be facilitated using the screen capture function of the PC.
4	PURPOSE: VERIFY RELATED PENDING CODE AND/OR DTC •  Switch the ignition off, then ON (engine off). •  Perform the Pending Trouble Code Access Procedure and DTC Reading Procedure. (See ON-BOARD DIAGNOSTIC TEST [SKYACTIV-G 2.0, SKYACTIV-G 2.5].) •  Are any other PENDING CODEs and/or DTCs present?	Yes	Go to the applicable PENDING CODE or DTC inspection. (See DTC TABLE [SKYACTIV-G 2.0, SKYACTIV-G 2.5].) Go to the next step.
		No	Go to the next step.
5	PURPOSE: VERIFY A/F SENSOR AND HO2S INPUT SIGNAL •  Start the engine and warm it up completely. •  Access the following PIDs using the M-MDS: (See ON-BOARD DIAGNOSTIC TEST [SKYACTIV-G 2.0, SKYACTIV-G 2.5].) ―  O2S11 ―  O2S12 •  Drive the vehicle under the following conditions. Warning •  When the M-MDS is used to observe monitor system status while driving, be sure to have another technician with you, or record the data in the M-MDS using the PID/DATA MONITOR AND RECORD capturing function and inspect later. •  While performing this step, always operate the vehicle in a safe and lawful manner. ―  After increasing the engine speed to 3,000 rpm, decelerate using engine braking. •  Is the displayed PID value as follows? ―  O2S11: 0.25 mA or more ―  O2S12: 0.3 V or less	Yes	Go to the troubleshooting procedure to perform the procedure from Step 3.
		No	Go to the next step.
6	INSPECT RELATED SENSOR WIRING HARNESS AND CONNECTOR •  Access the following PIDs using the M-MDS: (See ON-BOARD DIAGNOSTIC TEST [SKYACTIV-G 2.0, SKYACTIV-G 2.5].) ―  O2S11 ―  O2S12 •  When the PCM, A/F sensor and HO2S are shaken, does the PID value include a PID item which has changed?	Yes	Inspect the related wiring harness and connector. •  Repair or replace the malfunctioning part. Go to the troubleshooting procedure to perform the procedure from Step 8.
		No	Go to the troubleshooting procedure to perform the procedure from Step 1.

Troubleshooting Diagnostic Procedure

Intention of troubleshooting procedure

•  Step 1—2

―  Perform an inspection of the HO2S and A/F sensor signal related parts.

•  Step 3—7

―  Perform an inspection of each separate part.

•  Step 8—9

―  Verify that the primary malfunction is resolved and there are no other malfunctions.

STEP	INSPECTION	RESULTS	ACTION
1	PURPOSE: INSPECT INSTALLATION OF HO2S •  Inspect installation of HO2S. •  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 [SKYACTIV-G 2.0, SKYACTIV-G 2.5].)
2	PURPOSE: INSPECT INSTALLATION OF A/F SENSOR •  Inspect installation of A/F sensor. •  Is the A/F sensor installed securely?	Yes	Replace the A/F sensor and/or HO2S, then go to Step 8. (See AIR FUEL RATIO (A/F) SENSOR REMOVAL/INSTALLATION [SKYACTIV-G 2.0, SKYACTIV-G 2.5].) (See HEATED OXYGEN SENSOR (HO2S) REMOVAL/INSTALLATION [SKYACTIV-G 2.0, SKYACTIV-G 2.5].)
		No	Retighten the A/F sensor, then go to Step 8. (See AIR FUEL RATIO (A/F) SENSOR REMOVAL/INSTALLATION [SKYACTIV-G 2.0, SKYACTIV-G 2.5].)
3	PURPOSE: INSPECT INSTALLATION OF HO2S •  Inspect installation of HO2S. •  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 [SKYACTIV-G 2.0, SKYACTIV-G 2.5].)
4	PURPOSE: INSPECT INSTALLATION OF A/F SENSOR •  Inspect installation of A/F sensor. •  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 [SKYACTIV-G 2.0, SKYACTIV-G 2.5].)
5	PURPOSE: INSPECT EXHAUST SYSTEM FOR LEAKAGE •  Visually inspect for exhaust gas leakage from the exhaust system. •  Is there any malfunction?	Yes	Repair or replace the malfunctioning part according to the inspection results, then go to Step 8.
		No	Go to the next step.
6	PURPOSE: VERIFY IF OTHER DTCs ARE DISPLAYED •  Reconnect all disconnected connectors. •  Clear the DTC from the PCM memory using the M-MDS. (See AFTER REPAIR PROCEDURE [SKYACTIV-G 2.0, SKYACTIV-G 2.5].) •  Implement the repeatability verification procedure. (See Repeatability Verification Procedure.) •  Perform the Pending Trouble Code Access Procedure and DTC Reading Procedure. (See ON-BOARD DIAGNOSTIC TEST [SKYACTIV-G 2.0, SKYACTIV-G 2.5].) •  Are any other PENDING CODEs and/or DTCs present?	Yes	Go to the applicable PENDING CODE or DTC inspection. (See DTC TABLE [SKYACTIV-G 2.0, SKYACTIV-G 2.5].) Go to the next step.
		No	Go to the next step.
7	PURPOSE: VERIFY CATALYTIC CONVERTER (WU-TWC) MALFUNCTION •  Clear the DTC from the PCM memory using the M-MDS. (See AFTER REPAIR PROCEDURE [SKYACTIV-G 2.0, SKYACTIV-G 2.5].) •  Implement the repeatability verification procedure. (See Repeatability Verification Procedure.) •  Perform the Pending Trouble Code Access Procedure. (See ON-BOARD DIAGNOSTIC TEST [SKYACTIV-G 2.0, SKYACTIV-G 2.5].) •  Is the PENDING CODE for this DTC present?	Yes	Replace the exhaust manifold, then go to the next step. (See EXHAUST SYSTEM REMOVAL/INSTALLATION [SKYACTIV-G 2.0, SKYACTIV-G 2.5].)
		No	DTC troubleshooting completed.
8	PURPOSE: VERIFICATION OF VEHICLE REPAIR COMPLETION •  Always reconnect all disconnected connectors. •  Clear the DTC from the PCM memory using the M-MDS. (See AFTER REPAIR PROCEDURE [SKYACTIV-G 2.0, SKYACTIV-G 2.5].) •  Implement the repeatability verification procedure. (See Repeatability Verification Procedure.) •  Perform the Pending Trouble Code Access Procedure. (See ON-BOARD DIAGNOSTIC TEST [SKYACTIV-G 2.0, SKYACTIV-G 2.5].) •  Is the PENDING CODE for this DTC present?	Yes	Repeat the inspection from Step 1. •  If the malfunction recurs, replace the PCM. (See PCM REMOVAL/INSTALLATION [SKYACTIV-G 2.0, SKYACTIV-G 2.5].) Go to the next step.
		No	Go to the next step.
9	PURPOSE: VERIFY IF THERE IS ANY OTHER MALFUNCTION •  Is any other DTC or pending code stored?	Yes	Go to the applicable DTC inspection. (See DTC TABLE [SKYACTIV-G 2.0, SKYACTIV-G 2.5].)
		No	DTC troubleshooting completed.