LEMON Manuals: Even more car manuals for everyone
Home >> Subaru >> 2021 >> Crosstrek Hybrid >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 22 (Engine Control System (2.0L (Except For HEV)) (Diagnostics) (1 Of 4)) >> Diagnostic Procedure With Diagnostic Trouble Code (DTC) >> DTC P0031: A/F/O2 Heater Control Circuit Low Bank 1 Sensor 1 >> Notes

DTC P0031: A/F/O2 Heater Control Circuit Low Bank 1 Sensor 1: Notes

WARNING: This page is about a different variant/trim than selected.
  1. - 

    DTC detecting condition: 

    Immediately at fault recognition

    Wiring diagram: 

    Engine Electrical System Ref. to WIRING SYSTEM (IMPREZA MODEL)>ENGINE ELECTRICAL SYSTEM>WIRING DIAGRAM . Ref. to WIRING SYSTEM (CROSSTREK MODEL (EXCEPT FOR HEV))>ENGINE ELECTRICAL SYSTEM>WIRING DIAGRAM .

    • IMPREZA MODEL
    G13608025Courtesy of SUBARU OF AMERICA, INC.
    • CROSSTREK MODEL
    G13608026Courtesy of SUBARU OF AMERICA, INC.
    CAUTION: Use the check board when measuring the ECM terminal voltage and resistance. Ref. to ENGINE (DIAGNOSTICS) (H4DO 2.0 (EXCEPT FOR HEV))>GENERAL DESCRIPTION>PREPARATION TOOL>HOW TO USE CHECK BOARD .
    NOTE: After the faulty parts are repaired or replaced, perform the final check in Basic Diagnostic Procedure. Ref. to ENGINE (DIAGNOSTICS) (H4DO 2.0 (EXCEPT FOR HEV))>BASIC DIAGNOSTIC PROCEDURE>PROCEDURE .
  1. CHECK POWER SUPPLY TO FRONT OXYGEN (A/F) SENSOR  .
    1. Turn the ignition switch to OFF.
    2. Disconnect the connector from the front oxygen (A/F) sensor.
    3. Turn the ignition switch to ON.
    4. Measure the voltage between front oxygen (A/F) sensor connector and engine ground.

      Connector and terminal 

      (B379) No. 2 (+) - Engine ground (-):

      Is the voltage 10 V or more?

      Yes:  Go to  2.

      No:  Repair the power supply line.

      NOTE: In this case, repair the following item:
      • Open circuit of harness between main relay connector and front oxygen (A/F) sensor connector
      • Poor contact of main relay connector
      • Defective main relay
  2. CHECK HARNESS BETWEEN ECM AND FRONT OXYGEN (A/F) SENSOR (OPEN)  .
    1. Turn the ignition switch to OFF.
    2. Disconnect the connector from ECM.
    3. Measure the resistance between ECM connector and front oxygen (A/F) sensor connector.

      Connector and terminal 

      (E158) No. 88 - (B379) No. 1:

      Is the resistance less than 1 Ω?

      Yes:  Go to  3.

      No:  Check the harnesses and connectors, and repair or replace them if necessary.

      NOTE: In this case, repair the following item:
      • Open circuit in harness between ECM connector and front oxygen (A/F) sensor connector
      • Poor contact of coupling connector
  3. CHECK GROUND CIRCUIT FOR ECM (OPEN CIRCUIT)  .

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

    Connector and terminal 

    (B134) No. 69 - Chassis ground:

    (B134) No. 70 - Chassis ground:

    (B134) No. 71 - Chassis ground:

    (B134) No. 72 - Chassis ground:

    Is the resistance less than 5 Ω?

    Yes:  Go to  4.

    No:  Check the harnesses and connectors, and repair or replace them if necessary.

    NOTE: In this case, repair the following item:
    • Open circuit of harness between ECM connector and engine ground
    • Poor contact of coupling connector
  4. CHECK FRONT OXYGEN (A/F) SENSOR  .

    Check the front oxygen (A/F) sensor. Ref. to FUEL INJECTION (FUEL SYSTEMS) (H4DO (EXCEPT FOR HEV))>FRONT OXYGEN (A/F) SENSOR>INSPECTION .

    Is the check result OK?

    Yes:  Repair the poor contact of ECM connector.

    No:  Replace the front oxygen (A/F) sensor. Ref. to FUEL INJECTION (FUEL SYSTEMS) (H4DO (EXCEPT FOR HEV))>FRONT OXYGEN (A/F) SENSOR .

scientia non olet · About LEMON Manuals