DTC B1508: Rear Differential Oil Temperature Sensor Open Detected

DTC detecting condition: 

Detected when the following status for the oil temperature continues for 1.5 seconds:

• -5°C (-58°F) or less (77960 Ω or more)
• 200°C (392°F) or more (24 Ω or less)

Trouble symptom: 

Rear differential oil temperature warning light blinks.

Wiring diagram: 

Rear differential oil temperature warning light system Ref. to WIRING SYSTEM>REAR DIFFERENTIAL OIL TEMPERATURE WARNING LIGHT SYSTEM>WIRING DIAGRAM .

Courtesy of SUBARU OF AMERICA, INC.

1. CHECK DTC  .
   1. Turn the ignition switch to ON.
   2. Read the DTC of [Combination Meter] using the Subaru Select Monitor. Ref. to COMBINATION METER (DIAGNOSTICS)>DIAGNOSTIC TROUBLE CODE (DTC) .

   Is DTC B1508 displayed? (Current code)

   Yes:  Go to  2.

   No:  Go to  6.

2. CHECK DATA MONITOR  .

   Using the Subaru Select Monitor, check the following items in the [Data monitor] of [Combination Meter]. Ref. to COMBINATION METER (DIAGNOSTICS)>DATA MONITOR .

   • Ambient rear diff oil temperature

   Is [Ambient rear diff oil temperature] displayed?

   Yes:  Even if DTC is displayed, 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.

   No:  Go to  3.

3. CHECK HARNESS (OPEN CIRCUIT)  .
   1. Turn the ignition switch to OFF.
   2. Disconnect the combination meter connector and oil temperature sensor connector.
   3. Using the tester, measure the resistance between terminals.

      Connector & terminal 

      (i10) No. 16 - (R11) No. 1:

      (i10) No. 20 - (R11) No. 2:

   Is the resistance 10 Ω or less?

   Yes:  Go to  4.

   No:  Repair the open circuit of harness or replace harness.

4. CHECK HARNESS (GROUND SHORT CIRCUIT)  .

   Using the tester, measure the resistance between terminals.

   Connector & terminal 

   (i10) No. 16 - Chassis ground:

   (i10) No. 20 - Chassis ground:

   Is the resistance 10 Ω or less?

   Yes:  Repair the short circuit of harness or replace harness.

   No:  Go to  5.

5. CHECK OIL TEMPERATURE SENSOR  .

   Perform the inspection of oil temperature sensor unit. Ref. to DIFFERENTIALS>OIL TEMPERATURE SENSOR>INSPECTION .

   Is the check result OK?

   Yes:  Go to  6.

   No:  Replace the sensor. Ref. to DIFFERENTIALS>OIL TEMPERATURE SENSOR .

6. CHECK CONNECTOR  .
   1. Turn the ignition switch to OFF.
   2. Disconnect connectors.

   Is there poor contact of connector?

   Yes:  Repair or replace the poor contact of connector.

   No:  Even if DTC is displayed, 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.