DTC B2902: Rear Height Sensor Circuit

DTC detecting condition: 

Rear vehicle height sensor error is detected for 10 seconds or more.

Trouble symptom: 

The auto headlight beam leveler does not operate.

Wiring diagram: 

Headlight beam leveler system Ref. to WIRING SYSTEM (IMPREZA MODEL)>HEADLIGHT BEAM LEVELER SYSTEM>WIRING DIAGRAM . Ref. to WIRING SYSTEM (CROSSTREK MODEL (EXCEPT FOR HEV))>HEADLIGHT BEAM LEVELER SYSTEM>WIRING DIAGRAM .

Courtesy of SUBARU OF AMERICA, INC.

1. CHECK DTC  .
   1. Turn the ignition switch to OFF → ON.
   2. Turn on the headlight low beam.
   3. Using the Subaru Select Monitor, perform the clear memory of [Headlight/Foglight]. Ref. to COMMON (DIAG)>CLEAR MEMORY .
   4. Read the DTC of [Headlight/Foglight] using the Subaru Select Monitor. Ref. to HEADLIGHT / FOGLIGHT (DIAGNOSTICS)>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 DATA MONITOR  .

   Using the Subaru Select Monitor, check the following items in the [Data Monitor] of [Headlight/Foglight]. Ref. to HEADLIGHT / FOGLIGHT (DIAGNOSTICS)>DATA MONITOR .

   • R Sensor Signal

   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. Ref. to LIGHTING SYSTEM>AUTO HEADLIGHT BEAM LEVELER CONTROL MODULE .

   No:  Go to  3.

3. CHECK DATA MONITOR  .
   1. Using the Subaru Select Monitor, check the following items in the [Data Monitor] of [Headlight/Foglight]. Ref. to HEADLIGHT / FOGLIGHT (DIAGNOSTICS)>DATA MONITOR .
      • R Sensor Signal
   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 REAR VEHICLE HEIGHT SENSOR  .
   1. Turn the ignition switch to OFF.
   2. Disconnect the connector from the rear vehicle height sensor.
   3. Turn the ignition switch to ON.
   4. Measure the voltage between the rear vehicle height sensor connector and chassis ground.

      Connector and terminal 

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

   Is the voltage 5 V ±0.25 V?

   Yes:  Go to  5.

   No:  Replace the auto headlight beam leveler control module. Ref. to LIGHTING SYSTEM>AUTO HEADLIGHT BEAM LEVELER CONTROL MODULE .

5. PERFORM UNIT INSPECTION OF REAR VEHICLE HEIGHT SENSOR  .
   1. Turn the ignition switch to OFF.
   2. Remove the rear vehicle height sensor.
   3. Perform the inspection of rear height sensor unit. Ref. to LIGHTING SYSTEM>REAR HEIGHT SENSOR>INSPECTION .

   Is the check result OK?

   Yes:  Go to  6.

   No:  Replace the rear height sensor. Ref. 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 and terminal 

      (B616) No. 3 - (R29) No. 1:

      (B616) No. 19 - (R29) No. 2:

      (B616) 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 and terminal 

   (B616) No. 3 - Chassis ground:

   (B616) No. 19 - Chassis ground:

   (B616) No. 12 - Chassis ground:

   Is the resistance 10 kΩ or more?

   Yes:  Replace the auto headlight beam leveler control module. Ref. to LIGHTING SYSTEM>AUTO HEADLIGHT BEAM LEVELER CONTROL MODULE .

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