P0141

DTC P0141 - REAR OXYGEN SENSOR HEATER CIRCUIT MALFUNCTION

DTC DETECTING CONDITION:
- Two consecutive driving cycles with fault.

CAUTION: After repair or replacement of faulty parts, conduct CLEAR MEMORY MODE and INSPECTION MODE. Refer to How To Clear Diagnostic Trouble Codes. Clear Memory Mode




WIRING DIAGRAM

10R1: CHECK GROUND CIRCUIT OF ECM.
1. Turn ignition switch to OFF.
2. Disconnect connector from ECM.

Connector & Terminal (B134) No.35 - Chassis ground:

3. Measure resistance of harness between ECM connector and chassis ground.

CHECK: Is the resistance less than 5 ohms?

YES: Go to step 10R3.

NO: Go to step 10R2.

10R2: CHECK GROUND CIRCUIT OF ECM.
1. Repair harness and connector.

NOTE:
In this case, repair the following:
- Open circuit in harness between ECM and engine ground terminal.
- Poor contact in ECM connector.
- Poor contact in coupling connector (B22).

Connector & Terminal (B134) No.34 - Chassis ground:

2. Measure resistance of harness between ECM connector and chassis ground.

CHECK: Is the resistance less than 5 ohms?

YES: Go to step 10R3.

NO: Repair harness and connector.

NOTE:
In this case, repair the following:
- Open circuit in harness between ECM and engine ground terminal.
- Poor contact in ECM connector.
- Poor contact in coupling connector (B22).

10R3: CHECK CURRENT DATA.
1. Start engine.
2. Read data of rear oxygen sensor heater current using Subaru Select Monitor or OBD-II general scan tool.

NOTE:
- Subaru Select Monitor
For detailed operation procedure, Refer to the "READ CURRENT DATA SHOWN ON DISPLAY FOR ENGINE". Refer to Normal Scan Data Values.
- OBD-II scan tool
For detailed operation procedures, Refer to the OBD-II General Scan Tool Instruction Manual.

CHECK: Is the value more than 0.2A?

YES: Repair connector.

NOTE:
In this case, repair the following:
- Poor contact in rear oxygen sensor connector.
- Poor contact in rear oxygen sensor connecting harness connector.
- Poor contact in ECM connector .

NO: Go to step 10R4.

10R4: CHECK OUTPUT SIGNAL FROM ECM.
1. Start and idle the engine.

Connector & Terminal (B134) No.21 (+) - Chassis ground (-):

2. Measure voltage between ECM connector and chassis ground.

CHECK: Is the voltage less than 1.0 V?

YES: Go to step 10R7.

NO: Go to step 10R5.

10R5: CHECK OUTPUT SIGNAL FROM ECM.

Connector & Terminal (B134) No.21 (+) - Chassis ground (-):

Measure voltage between ECM connector and chassis ground.

CHECK: Does the voltage change less than 1.0 Volt by shaking harness and connector of ECM while monitoring the value with voltage meter?

YES: Repair poor contact in ECM connector.

NO: Go to step 10R6.

10R6: CHECK OUTPUT SIGNAL FROM ECM.
1. Disconnect connector from rear oxygen sensor.

Connector & Terminal (B134) No.21 (+) - Chassis ground (-):

2. Measure voltage between ECM connector and chassis ground.

CHECK: Is the voltage less than 1.0 V?

YES: Replace ECM.

NO: Repair battery short circuit in harness between ECM and rear oxygen sensor connector. After repair, replace ECM.

10R7: CHECK POWER SUPPLY TO REAR OXYGEN SENSOR.
1. Turn ignition switch to OFF
2. Disconnect connector from rear oxygen sensor.
3. Turn ignition switch to ON.

Connector & Terminal (E25) No.2 (+) - Chassis ground (-):

4. Measure voltage between rear oxygen sensor connector and engine ground or chassis ground.

CHECK: Is the voltage more than 10 V?

YES: Go to step 10R8.

NO: Repair power supply line.

NOTE:
In this case, repair the following:
- Open circuit in harness between main relay and rear oxygen sensor connector.
- Poor contact in rear oxygen sensor connector.
- Poor contact in coupling connector (E1).

10R8: CHECK REAR OXYGEN SENSOR.
1. Turn ignition switch to OFF

Terminals No.1 - No.2:

2. Measure resistance between rear oxygen sensor connector terminals.

CHECK: Is the resistance less than 30 ohms?

YES: Repair harness and connector.

NOTE:
In this case, repair the following:
- Open circuit in harness between rear oxygen sensor and ECM connector.
- Poor contact in rear oxygen sensor connector.
- Poor contact in ECM connector.
- Poor contact in coupling connector (E1).

NO: Replace rear oxygen sensor.