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DTC P0421:00 [PCM (SKYACTIV-X)]

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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 (GPF) is activated sufficiently.

•  A/F sensor is activated sufficiently.

•  HO2S is activated sufficiently.

•  The following DTCs are not detected:

―  Misfire: P0300:00, P0301:00, P0302:00, P0303:00 and P0304:00

―  Fuel injection correction: P0171:00, P0172:00, P2096:00 and P2097:00

―  A/F sensor: P0130:00, P0131:00, P0132:00, P0133:00, P0134:00, P064D:00, P2237:00, P2243:00 and P2251:00

―  HO2S: P0137:00, P0138:00, P013A:00 and P0140:00

―  A/F sensor heater: P0031:00 and P0032:00

―  HO2S heater: P0037:00 and P0038:00

Drive cycle

•  2

Self test type

•  CMDTC self test

Sensor used

•  A/F sensor, HO2S

Fail-safe function

•  Inhibits the EGR control.

Vehicle status when DTCs are output

•  Not applicable

Possible cause

•  HO2S malfunction

―  HO2S incorrect installation

•  A/F sensor malfunction

―  A/F sensor incorrect installation

―  Exhaust system leakage

―  A/F sensor deterioration

•  Catalytic converter (GPF) deterioration or malfunction

•  PCM malfunction

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 (GPF) is activated sufficiently. • A/F sensor is activated sufficiently. • HO2S is activated sufficiently. • The following DTCs are not detected: ― Misfire: P0300:00, P0301:00, P0302:00, P0303:00 and P0304:00 ― Fuel injection correction: P0171:00, P0172:00, P2096:00 and P2097:00 ― A/F sensor: P0130:00, P0131:00, P0132:00, P0133:00, P0134:00, P064D:00, P2237:00, P2243:00 and P2251:00 ― HO2S: P0137:00, P0138:00, P013A:00 and P0140:00 ― A/F sensor heater: P0031:00 and P0032:00 ― HO2S heater: P0037:00 and P0038:00
Drive cycle	• 2
Self test type	• CMDTC self test
Sensor used	• A/F sensor, HO2S
Fail-safe function	• Inhibits the EGR control.
Vehicle status when DTCs are output	• Not applicable
Possible cause	• HO2S malfunction ― HO2S incorrect installation • A/F sensor malfunction ― A/F sensor incorrect installation ― Exhaust system leakage ― A/F sensor deterioration • Catalytic converter (GPF) 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 during deceleration.

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

• If the catalytic converter purification characteristic deteriorates, the amount of time until the HO2S detects the voltage on the rich side is shorter compared to the normal purification characteristic as shown in the 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/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/snapshot data.

PID Item/Simulation Item Used In Diagnosis

PID/DATA monitor item table

PIDs	Reference
A/F_SEN_CUR	(See PID/DATA MONITOR TABLE [PCM (SKYACTIV-X)].)
HO2S_OUT_VOLT	(See PID/DATA MONITOR TABLE [PCM (SKYACTIV-X)].)

Function Inspection Using M-MDS

Step

Inspection

Results

Action

1

PURPOSE: VERIFY RELATED REPAIR INFORMATION OR SERVICE INFORMATION AVAILABILITY

•  Verify related Service Bulletins, on-line repair information, or Service Information availability.

•  Is any related Information available?

Yes

Perform repair or diagnosis according to the available 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

•  Is the DTC P0421:00 on freeze frame data?

Yes

Go to the next step.

No

Go to the troubleshooting procedure for DTC on freeze frame data.

(See DTC TABLE [PCM (SKYACTIV-X)].)

3

PURPOSE: RECORD VEHICLE STATUS WHEN DTC WAS DETECTED TO UTILIZE WITH REPEATABILITY VERIFICATION

•  Record the freeze frame data/snapshot data.

Note

•  Recording can be facilitated using the screen capture function of the PC.

—

Go to the next step.

4

PURPOSE: INSPECT FOR OTHER RELATED DTCs

•  Perform the DTC inspection for the PCM.
(See DTC INSPECTION.)

•  Are any other DTCs displayed?

Yes

Repair the malfunctioning location according to the applicable DTC troubleshooting.

(See DTC TABLE [PCM (SKYACTIV-X)].)

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 PID/DATA MONITOR INSPECTION.)

―  A/F_SEN_CUR

―  HO2S_OUT_VOLT

•  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?

―  A/F_SEN_CUR: 0.25 mA or more

―  HO2S_OUT_VOLT: 0.3 V or less

Yes

Go to Troubleshooting Diagnostic Procedure to perform the procedure from Step 3.

No

Go to the next step.

6

PURPOSE: VERIFY CONNECTOR CONNECTIONS

•  Access the following PIDs using the M-MDS:
(See PID/DATA MONITOR INSPECTION.)

―  A/F_SEN_CUR

―  HO2S_OUT_VOLT

•  Does the PID value fluctuate when the following connectors are shaken?

―  A/F sensor

―  HO2S

―  PCM

Yes

Repair or replace the applicable wiring harness or connector parts.

Go to Troubleshooting Diagnostic Procedure to perform the repair completion verification.

No

Go to Troubleshooting Diagnostic Procedure to perform the procedure from Step 1.

Step	Inspection	Results	Action
1	PURPOSE: VERIFY RELATED REPAIR INFORMATION OR SERVICE INFORMATION AVAILABILITY • Verify related Service Bulletins, on-line repair information, or Service Information availability. • Is any related Information available?	Yes	Perform repair or diagnosis according to the available 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 • Is the DTC P0421:00 on freeze frame data?	Yes	Go to the next step.
No	Go to the troubleshooting procedure for DTC on freeze frame data. (See DTC TABLE [PCM (SKYACTIV-X)].)
3	PURPOSE: RECORD VEHICLE STATUS WHEN DTC WAS DETECTED TO UTILIZE WITH REPEATABILITY VERIFICATION • Record the freeze frame data/snapshot data. Note • Recording can be facilitated using the screen capture function of the PC.	—	Go to the next step.
4	PURPOSE: INSPECT FOR OTHER RELATED DTCs • Perform the DTC inspection for the PCM. (See DTC INSPECTION.) • Are any other DTCs displayed?	Yes	Repair the malfunctioning location according to the applicable DTC troubleshooting. (See DTC TABLE [PCM (SKYACTIV-X)].) 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 PID/DATA MONITOR INSPECTION.) ― A/F_SEN_CUR ― HO2S_OUT_VOLT • 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? ― A/F_SEN_CUR: 0.25 mA or more ― HO2S_OUT_VOLT: 0.3 V or less	Yes	Go to Troubleshooting Diagnostic Procedure to perform the procedure from Step 3.
No	Go to the next step.
6	PURPOSE: VERIFY CONNECTOR CONNECTIONS • Access the following PIDs using the M-MDS: (See PID/DATA MONITOR INSPECTION.) ― A/F_SEN_CUR ― HO2S_OUT_VOLT • Does the PID value fluctuate when the following connectors are shaken? ― A/F sensor ― HO2S ― PCM	Yes	Repair or replace the applicable wiring harness or connector parts. Go to Troubleshooting Diagnostic Procedure to perform the repair completion verification.
No	Go to Troubleshooting Diagnostic Procedure to perform the procedure from Step 1.

Troubleshooting Diagnostic Procedure

Intention of troubleshooting procedure

• Step 1—2

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

• Step 3—7

― Perform inspection of each separate part.

• Repair completion verification

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

Step

Inspection

Results

Action

1

PURPOSE: VERIFY IF HO2S IS INSTALLED CORRECTLY

•  Verify the HO2S installation condition.
(See HEATED OXYGEN SENSOR (HO2S) REMOVAL/INSTALLATION [SKYACTIV-X 2.0].)

•  Is the installation condition normal?

Yes

Go to the next step.

No

Correctly install the HO2S and perform the repair completion verification.

(See HEATED OXYGEN SENSOR (HO2S) REMOVAL/INSTALLATION [SKYACTIV-X 2.0].)

2

PURPOSE: VERIFY IF A/F SENSOR IS INSTALLED CORRECTLY

•  Verify the A/F sensor installation condition.
(See AIR FUEL RATIO (A/F) SENSOR REMOVAL/INSTALLATION [SKYACTIV-X 2.0].)

•  Is the installation condition normal?

Yes

Replace the A/F sensor and/or HO2S and perform the repair completion verification.

(See AIR FUEL RATIO (A/F) SENSOR REMOVAL/INSTALLATION [SKYACTIV-X 2.0].)

(See HEATED OXYGEN SENSOR (HO2S) REMOVAL/INSTALLATION [SKYACTIV-X 2.0].)

No

Correctly install the A/F sensor and perform the repair completion verification.

(See AIR FUEL RATIO (A/F) SENSOR REMOVAL/INSTALLATION [SKYACTIV-X 2.0].)

3

PURPOSE: VERIFY IF HO2S IS INSTALLED CORRECTLY

•  Verify the HO2S installation condition.
(See HEATED OXYGEN SENSOR (HO2S) REMOVAL/INSTALLATION [SKYACTIV-X 2.0].)

•  Is the installation condition normal?

Yes

Go to the next step.

No

Correctly install the HO2S and perform the repair completion verification.

(See HEATED OXYGEN SENSOR (HO2S) REMOVAL/INSTALLATION [SKYACTIV-X 2.0].)

4

PURPOSE: VERIFY IF A/F SENSOR IS INSTALLED CORRECTLY

•  Verify the A/F sensor installation condition.
(See AIR FUEL RATIO (A/F) SENSOR REMOVAL/INSTALLATION [SKYACTIV-X 2.0].)

•  Is the installation condition normal?

Yes

Go to the next step.

No

Correctly install the A/F sensor and perform the repair completion verification.

(See AIR FUEL RATIO (A/F) SENSOR REMOVAL/INSTALLATION [SKYACTIV-X 2.0].)

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 location and perform the repair completion verification.

No

Go to the next step.

6

PURPOSE: VERIFY IF OTHER DTCs ARE DISPLAYED

•  Install/connect the part removed/disconnected during the troubleshooting procedure.

•  Clear the DTC recorded in the memory.
(See CLEARING DTC.)

•  Implement the repeatability verification procedure.
(See Repeatability Verification Procedure.)

•  Perform the DTC inspection for the PCM.
(See DTC INSPECTION.)

•  Are any other DTCs displayed?

Yes

Repair the malfunctioning location according to the applicable DTC troubleshooting.

(See DTC TABLE [PCM (SKYACTIV-X)].)

Go to the next step.

No

Go to the next step.

7

PURPOSE: VERIFY CATALYTIC CONVERTER (GPF) MALFUNCTION

•  Clear the DTC recorded in the memory.
(See CLEARING DTC.)

•  Implement the repeatability verification procedure.
(See Repeatability Verification Procedure.)

•  Perform the DTC inspection for the PCM.
(See DTC INSPECTION.)

•  Is the same Pending DTC present?

Yes

Replace the catalytic converter (GPF) and perform the repair completion verification.

(See CATALYTIC CONVERTER (GPF) REMOVAL/INSTALLATION [SKYACTIV-X 2.0].)

No

DTC troubleshooting completed.

Repair completion verification 1

PURPOSE: VERIFY THAT VEHICLE IS REPAIRED

•  Install/connect the part removed/disconnected during the troubleshooting procedure.

•  Clear the DTC recorded in the memory.
(See CLEARING DTC.)

•  Replicate the vehicle conditions at the time the DTC was detected using the following procedure.

―  Implement the repeatability verification procedure.
(See Repeatability Verification Procedure.)

•  Perform the DTC inspection for the PCM.
(See DTC INSPECTION.)

•  Is the same Pending DTC present?

Yes

Refer to the controller area network (CAN) malfunction diagnosis flow to inspect for a CAN communication error.

(See CONTROLLER AREA NETWORK (CAN) MALFUNCTION DIAGNOSIS FLOW [(E)].)

If the CAN communication is normal, perform the diagnosis from Step 1.

•  If the malfunction recurs, replace the PCM, then go to the next step.
(See PCM REMOVAL/INSTALLATION [SKYACTIV-X 2.0].)

No

Go to the next step.

Repair completion verification 2

PURPOSE: VERIFY IF OTHER DTCs DISPLAYED

•  Perform the DTC inspection.
(See DTC INSPECTION.)

•  Are any other DTCs displayed?

Yes

Repair the malfunctioning location according to the applicable DTC troubleshooting.

No

DTC troubleshooting completed.

Step	Inspection	Results	Action
1	PURPOSE: VERIFY IF HO2S IS INSTALLED CORRECTLY • Verify the HO2S installation condition. (See HEATED OXYGEN SENSOR (HO2S) REMOVAL/INSTALLATION [SKYACTIV-X 2.0].) • Is the installation condition normal?	Yes	Go to the next step.
1		No	Correctly install the HO2S and perform the repair completion verification. (See HEATED OXYGEN SENSOR (HO2S) REMOVAL/INSTALLATION [SKYACTIV-X 2.0].)
2	PURPOSE: VERIFY IF A/F SENSOR IS INSTALLED CORRECTLY • Verify the A/F sensor installation condition. (See AIR FUEL RATIO (A/F) SENSOR REMOVAL/INSTALLATION [SKYACTIV-X 2.0].) • Is the installation condition normal?	Yes	Replace the A/F sensor and/or HO2S and perform the repair completion verification. (See AIR FUEL RATIO (A/F) SENSOR REMOVAL/INSTALLATION [SKYACTIV-X 2.0].) (See HEATED OXYGEN SENSOR (HO2S) REMOVAL/INSTALLATION [SKYACTIV-X 2.0].)
2		No	Correctly install the A/F sensor and perform the repair completion verification. (See AIR FUEL RATIO (A/F) SENSOR REMOVAL/INSTALLATION [SKYACTIV-X 2.0].)
3	PURPOSE: VERIFY IF HO2S IS INSTALLED CORRECTLY • Verify the HO2S installation condition. (See HEATED OXYGEN SENSOR (HO2S) REMOVAL/INSTALLATION [SKYACTIV-X 2.0].) • Is the installation condition normal?	Yes	Go to the next step.
3		No	Correctly install the HO2S and perform the repair completion verification. (See HEATED OXYGEN SENSOR (HO2S) REMOVAL/INSTALLATION [SKYACTIV-X 2.0].)
4	PURPOSE: VERIFY IF A/F SENSOR IS INSTALLED CORRECTLY • Verify the A/F sensor installation condition. (See AIR FUEL RATIO (A/F) SENSOR REMOVAL/INSTALLATION [SKYACTIV-X 2.0].) • Is the installation condition normal?	Yes	Go to the next step.
4		No	Correctly install the A/F sensor and perform the repair completion verification. (See AIR FUEL RATIO (A/F) SENSOR REMOVAL/INSTALLATION [SKYACTIV-X 2.0].)
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 location and perform the repair completion verification.
5		No	Go to the next step.
6	PURPOSE: VERIFY IF OTHER DTCs ARE DISPLAYED • Install/connect the part removed/disconnected during the troubleshooting procedure. • Clear the DTC recorded in the memory. (See CLEARING DTC.) • Implement the repeatability verification procedure. (See Repeatability Verification Procedure.) • Perform the DTC inspection for the PCM. (See DTC INSPECTION.) • Are any other DTCs displayed?	Yes	Repair the malfunctioning location according to the applicable DTC troubleshooting. (See DTC TABLE [PCM (SKYACTIV-X)].) Go to the next step.
6		No	Go to the next step.
7	PURPOSE: VERIFY CATALYTIC CONVERTER (GPF) MALFUNCTION • Clear the DTC recorded in the memory. (See CLEARING DTC.) • Implement the repeatability verification procedure. (See Repeatability Verification Procedure.) • Perform the DTC inspection for the PCM. (See DTC INSPECTION.) • Is the same Pending DTC present?	Yes	Replace the catalytic converter (GPF) and perform the repair completion verification. (See CATALYTIC CONVERTER (GPF) REMOVAL/INSTALLATION [SKYACTIV-X 2.0].)
7		No	DTC troubleshooting completed.
Repair completion verification 1	PURPOSE: VERIFY THAT VEHICLE IS REPAIRED • Install/connect the part removed/disconnected during the troubleshooting procedure. • Clear the DTC recorded in the memory. (See CLEARING DTC.) • Replicate the vehicle conditions at the time the DTC was detected using the following procedure. ― Implement the repeatability verification procedure. (See Repeatability Verification Procedure.) • Perform the DTC inspection for the PCM. (See DTC INSPECTION.) • Is the same Pending DTC present?	Yes	Refer to the controller area network (CAN) malfunction diagnosis flow to inspect for a CAN communication error. (See CONTROLLER AREA NETWORK (CAN) MALFUNCTION DIAGNOSIS FLOW [(E)].) If the CAN communication is normal, perform the diagnosis from Step 1. • If the malfunction recurs, replace the PCM, then go to the next step. (See PCM REMOVAL/INSTALLATION [SKYACTIV-X 2.0].)
Repair completion verification 1		No	Go to the next step.
Repair completion verification 2	PURPOSE: VERIFY IF OTHER DTCs DISPLAYED • Perform the DTC inspection. (See DTC INSPECTION.) • Are any other DTCs displayed?	Yes	Repair the malfunctioning location according to the applicable DTC troubleshooting.
Repair completion verification 2		No	DTC troubleshooting completed.