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)
• 20°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. 

   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 malfunction)

   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 and 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 and 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.