DTC P0038: A/F/O2 Heater Control Circuit High Bank 1 Sensor 2: Notes

DTC detecting condition: 

Detected when two consecutive driving cycles with fault occur.

Wiring diagram: 

Engine Electrical System Refer to WIRING SYSTEM>ENGINE ELECTRICAL SYSTEM>WIRING DIAGRAM .

Courtesy of SUBARU OF AMERICA, INC.

1. CHECK HARNESS BETWEEN ECM AND REAR OXYGEN SENSOR CONNECTOR. 
   1. Turn the ignition switch to OFF.
   2. Measure the voltage between ECM connector and chassis ground.

      Connector & terminal 

      (B135) No. 6 (+) - Chassis ground (-):

   Is the voltage 10 V or more?

   Yes:  Repair the short circuit to power in the harness between ECM connector and rear oxygen sensor connector.

   No:  Go to  2.

2. CHECK GROUND CIRCUIT FOR ECM. 
   1. Disconnect the connector from ECM.
   2. Measure the resistance between ECM connector and chassis ground.

      Connector & terminal 

      (B134) No. 3 - Chassis ground:

      (B134) No. 4 - Chassis ground:

      (B134) No. 6 - Chassis ground:

      (B137) No. 1 - Chassis ground:

      (B137) No. 3 - Chassis ground:

   Is the resistance less than 5 Ω?

   Yes:  Repair the poor contact of ECM connector.

   No:  Repair the harness and connector.

   NOTE: In this case, repair the following item:

   • Open circuit of harness between ECM connector and engine ground
   • Poor contact of coupling connector