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Home >> Subaru >> 2019 >> Forester Base >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System (Diagnostics) (4 Of 4) >> Diagnostic Procedure with Diagnostic Trouble Code (DTC) >> DTC P26A6: Engine Coolant Bypass Valve "A" Position Sensor Circuit Low >> Notes

DTC P26A6: Engine Coolant Bypass Valve "A" Position Sensor Circuit Low: Notes

  1. - 

    DTC detecting condition: 

    Immediately at fault recognition

    Trouble symptom: 

    • Coolant temperature rises slowly
    • Poor acceleration

    Wiring diagram: 

    Engine Electrical System Ref. to WIRING SYSTEM>ENGINE ELECTRICAL SYSTEM .

G13228157Courtesy of SUBARU OF AMERICA, INC.
CAUTION: Use the check board when measuring the ECM terminal voltage and resistance. Ref. to ENGINE (DIAGNOSTICS) (H4DO)>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)>BASIC DIAGNOSTIC PROCEDURE>PROCEDURE .
  1. CHECK DATA MONITOR  .
    1. Start the engine.
    2. Using the Subaru Select Monitor, read the value in [Coolant Circulation Valve Actual Angle].
      NOTE: For detailed operation procedures, refer to "Common (Diagnostics)". Ref. to COMMON(DIAG)>DATA MONITOR .

    Is the value of [Coolant Circulation Valve Actual Angle] approx. -95 deg or less?

    Yes

    Go to  2 .

    No

    Even if DTC is detected, the circuit has returned to a normal condition at this time.

    Reproduce the failure, and then perform the diagnosis again.

    NOTE: In this case, temporary poor contact of connector, temporary open or short circuit of harness may be the cause.
  2. CHECK HARNESS BETWEEN ECM AND THERMO-CONTROL VALVE ASSEMBLY CONNECTOR (OPEN)  .
    1. Turn the ignition switch to OFF.
    2. Disconnect the connector from ECM.
    3. Disconnect the connector from the thermo-control valve assembly.
    4. Measure the resistance between ECM connector and thermo-control valve assembly connector.

      Connector & terminal 

      (E158) No. 17 - (E164) No. 3:

      (E158) No. 41 - (E164) No. 1:

    Is the resistance less than 1 Ω?

    Yes

    Go to  3 .

    No

    Repair the open circuit of the harness between the ECM connector and thermo-control valve assembly connector.

  3. CHECK HARNESS BETWEEN ECM AND THERMO-CONTROL VALVE ASSEMBLY CONNECTOR (SHORT CIRCUIT TO GROUND)  .

    Measure the resistance between the ECM connector and engine ground.

    Connector & terminal 

    (E158) No. 17 - Engine ground:

    (E158) No. 41 - Engine ground:

    Is the resistance 1 MΩ or more?

    Yes

    Go to  4 .

    No

    Repair the short circuit to ground in the harness between the ECM connector and thermo-control valve assembly connector.

  4. CHECK HARNESS BETWEEN ECM AND THERMO-CONTROL VALVE ASSEMBLY CONNECTOR (SHORT TO POWER SUPPLY)  .
    1. Connect the connector to ECM.
    2. Turn the ignition switch to ON.
    3. Measure the voltage between thermo-control valve assembly connector and engine ground.

      Connector & terminal 

      (E164) No. 1 (+) - Engine ground (-):

    Is the voltage 4.5 - 5.5 V?

    Yes

    Go to  5 .

    No

    Repair the short circuit to power supply in the harness between the ECM connector and thermo-control valve assembly connector.

  5. CHECK FOR POOR CONTACT  .

    Check the connection status of ECM connector and thermo-control valve assembly connector.

    Is there poor contact of ECM connector or thermo-control valve assembly connector?

    Yes

    Repair poor contact of ECM connector or thermo-control valve assembly connector.

    No

    Replace the thermo-control valve assembly. Ref. to COOLING (H4DO)>THERMO CONTROL VALVE ASSEMBLY .

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