P0135

P: DTC PO135 - FRONT 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 and INSPECTION MODES. Clearing Diagnostic Trouble Codes





WIRING DIAGRAM

CHECK: Does the Subaru Select Monitor or OBD-II general scan tool indicate DTC P0135 and P0141 at the same time?

YES: Go to step 10P2.

NO: Go to step 10P4.

10P2: 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 10P4.

NO: Go to step 10P3.

10P3: 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 (B21)

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 10P4.

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 (B21)

10P4: CONNECT SUBARU SELECT MONITOR OR THE OBD-II GENERAL SCAN TOOL, AND READ DATA.
1) Turn ignition switch to OFF.





2) Connect Subaru Select Monitor or the OBD-II general scan tool to data link connector.

3) Turn ignition switch to ON and Subaru Select Monitor or OBD-II general scan tool switch to ON.

4) Start engine.

5) Read data of front 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".
- OBD-II scan tool
For detailed operation procedures, refer to the OBD-II General Scan Tool Instruction Manual.

CHECK: Is the value more than 0.2 A?

YES: Repair connector.

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

NO: Go to step 10P5.

10P5: CHECK OUTPUT SIGNAL FROM ECM.
1) Start and idle the engine.

Connector & Terminal (B134) No.22 (+) - Chassis Ground (-):

2) Measure voltage between ECM connector and chassis ground.

CHECK: Is the voltage less than 1.0 V?

YES: Go to step 10P11.

NO: Go to step 10P6.

10P6: CHECK OUTPUT SIGNAL FROM ECM.

Connector & Terminal (B134) No.22 (+) - Chassis Ground (-):

Measure voltage between ECM connector and chassis ground.

CHECK: Does the voltage change less than 1.0 V 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 10P7.

10P7: CHECK OUTPUT SIGNAL FROM ECM.

Connector & Terminal (B134) No.23 (+) - Chassis Ground (-):

Measure voltage between ECM connector and chassis ground.

CHECK: Is the voltage less than 1.0 V?

YES: Go to step 10P11.

NO: Go to step 10P8.

10P8: CHECK OUTPUT SIGNAL FROM ECM.

Connector & Terminal (B134) No.23 (+) - Chassis Ground (-):

Measure voltage between ECM connector and chassis ground.

CHECK: Does the voltage change less than 1.0 V 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 10P9.

10P9: CHECK OUTPUT SIGNAL FROM ECM.
1) Disconnect connector from front oxygen sensor.

Connector & Terminal (B134) No.22 (+) - Chassis Ground (-):

2) Measure voltage between ECM connector and chassis ground.

CHECK: Is the voltage less than 1.0 V?

YES: Go to step 10P10.

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

10P10: CHECK OUTPUT SIGNAL FROM ECM.

Connector & Terminal (B134) No.23 (+) - Chassis Ground (-):

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 front oxygen sensor connector. After repair, replace ECM.

10P11: CHECK POWER SUPPLY TO FRONT OXYGEN SENSOR.
1) Turn ignition switch to OFF.

2) Disconnect connector from front oxygen sensor.

3) Turn ignition switch to ON.

Connector & Terminal (E24) No.2 (+) - Engine Ground (-):

4) Measure voltage between front oxygen sensor connector and engine ground.

CHECK: Is the voltage more than 10 V?

YES: Go to step 10P12.

NO: Repair power supply line.

NOTE:
In this case, repair the following:
- Open circuit in harness between main relay and front oxygen sensor connector
- Poor contact in front oxygen sensor connector
- Poor contact in main relay connector

10P12: CHECK FRONT OXYGEN SENSOR.
1) Turn ignition switch to OFF.

Connector & Terminal (E24) No.2 (+) - Engine Ground (-):

2) Measure resistance between front 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 front oxygen sensor and ECM connector
- Poor contact in front oxygen sensor connector
- Poor contact in ECM connector

NO: Replace front oxygen sensor.