DTC B2902: Rear Height Sensor Circuit

DTC detecting condition: 

Detected when error occurs in the rear height sensor.

Trouble symptom: 

The auto headlight beam leveler does not operate.

Wiring diagram: 

Headlight beam leveler system. Refer to WIRING SYSTEM>HEADLIGHT BEAM LEVELER SYSTEM>WIRING DIAGRAM .

Courtesy of SUBARU OF AMERICA, INC.

1. CHECK DTC. 
   1. Turn the ignition switch OFF → ON.
   2. Turn on the headlight low beam.
   3. Using the Subaru Select Monitor, clear the auto headlight beam leveler system memory. Refer to AUTO HEADLIGHT BEAM LEVELER SYSTEM (DIAGNOSTICS)>CLEAR MEMORY MODE .
   4. Turn the ignition switch to OFF → ON.
   5. Read the DTC using Subaru Select Monitor. Refer to AUTO HEADLIGHT BEAM LEVELER SYSTEM (DIAGNOSTICS)>READ DIAGNOSTIC TROUBLE CODE (DTC) .

      Is DTC B2902 displayed? (Current malfunction)

      Yes:  Go to  2.

      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.
2. CHECK CURRENT DATA. 

   Display «R Sensor Signal» using Subaru Select Monitor. Refer to AUTO HEADLIGHT BEAM LEVELER SYSTEM (DIAGNOSTICS)>READ CURRENT DATA .

   Does the data indicate the standard value (approx. 2.5 V when on a level road with one person in the vehicle)?

   Yes:  Replace the auto headlight beam leveler Control Module. Refer to LIGHTING SYSTEM>AUTO HEADLIGHT BEAM LEVELER CONTROL MODULE .

   No:  Go to  3.

3. CHECK CURRENT DATA. 
   1. Display «R Sensor Signal» using Subaru Select Monitor. Refer to AUTO HEADLIGHT BEAM LEVELER SYSTEM (DIAGNOSTICS)>READ CURRENT DATA .
   2. Change the vehicle posture.

      Does the data change?

      Yes:  Go to  6.

      No:  Go to  4.

4. CHECK OUTPUT VOLTAGE BETWEEN AUTO HEADLIGHT BEAM LEVELER Control Module AND VEHICLE HEIGHT SENSOR. 
   1. Disconnect the vehicle height sensor connector.
   2. Turn the ignition switch to ON.
   3. Measure the voltage between the vehicle height sensor connector and chassis ground.

      Connector & terminal

      (R29) No. 3 (+) - Chassis ground (-):

      Is the voltage 5±0.25 V?

      Yes:  Go to  5.

      No:  Replace the auto headlight beam leveler Control Module. Refer to LIGHTING SYSTEM>AUTO HEADLIGHT BEAM LEVELER CONTROL MODULE .

5. CHECK REAR HEIGHT SENSOR. 
   1. Remove the rear vehicle height sensor.
   2. Perform the inspection of rear height sensor unit. Refer to LIGHTING SYSTEM>REAR HEIGHT SENSOR>INSPECTION .

      Is the check result OK?

      Yes:  Go to  6.

      No:  Replace the rear height sensor. Refer to LIGHTING SYSTEM>REAR HEIGHT SENSOR .

6. CHECK HARNESS (OPEN CIRCUIT). 
   1. Disconnect the auto headlight beam leveler Control Module connector.
   2. Using a tester, measure the resistance between the auto headlight beam leveler Control Module connector and rear height sensor connector.

      Connector & terminal

      (B150) No. 3 - (R29) No. 1:

      (B150) No. 19 - (R29) No. 2:

      (B150) No. 12 - (R29) No. 3:

      Is there continuity?

      Yes:  Go to  7.

      No:  Repair or replace the open circuit of harness.

7. CHECK HARNESS (GROUND SHORT CIRCUIT). 

   Using a tester, measure the resistance between the auto headlight beam leveler Control Module connector and chassis ground.

   Connector & terminal

   (B150) No. 3 - Chassis ground:

   (B150) No. 19 - Chassis ground:

   (B150) No. 12 - Chassis ground:

   Is the resistance 10 kΩ or more?

   Yes:  Replace the auto headlight beam leveler Control Module. Refer to LIGHTING SYSTEM>AUTO HEADLIGHT BEAM LEVELER CONTROL MODULE .

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