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

DTC detecting condition:

Immediately at fault recognition

Trouble symptom:

Coolant temperature rises slowly
Poor acceleration

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 .

Wiring diagram:

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

Courtesy of SUBARU OF AMERICA, INC.

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 2.

No: Repair the open circuit of the harness between the ECM connector and thermo-control valve assembly connector.
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 3.

No: Repair the short circuit to ground in the harness between the ECM connector and thermo-control valve assembly connector.
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 4.

No: Repair the short circuit to power supply in the harness between the ECM connector and thermo-control valve assembly connector.
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 .