DTC B2255: USB2 (Data Communication Module) FAULTS

DTC detecting condition: 

• Detected when a Data Communication Module that operates properly is not connected via USB.
• Detected when the Data Communication Module is not connected via USB.

Trouble symptom: 

Communication between audio or navigation unit and Data Communication Module is impossible.

1. CHECK DTC. 
   1. Turn the ignition switch to ON.
   2. Using the Subaru Select Monitor, perform the clear memory of [Infotainment]. Ref. to COMMON (DIAG)>CLEAR MEMORY .
   3. Turn the ignition switch OFF → ON.
   4. Read the DTC of [Infotainment] using the Subaru Select Monitor. Ref. to INFOTAINMENT (DIAGNOSTICS)>DIAGNOSTIC TROUBLE CODE (DTC) .

   Is DTC B2255 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 CONNECTION OF CONNECTOR AND HARNESS 
   1. Turn the ignition switch to OFF.
   2. Check if the connectors of the audio or navigation unit and DCM are firmly connected.

   Is the check result OK?

   Yes:  Go to  3

   No:  Connect the connector.

3. CHECK CONNECTOR AND HARNESS 

   Visually check the connector, terminal or harness body.

   Is the check result OK?

   Yes:  Go to  4

   No:  Repair or replace the harness

4. CHECK HARNESS (OPEN CIRCUIT). 
   1. Turn the ignition switch to OFF.
   2. Disconnect the audio connector or navigation unit connector.
   3. Disconnect the DCM connector.
   4. Using a tester, measure the resistance between audio connector or navigation unit connector and DCM connector.

      Connector & terminal

      (AD77) No. 1 - (AD78) No. 2:

      (AD77) No. 2 - (AD78) No. 3:

      (AD77) No. 3 - (AD78) No. 1:

      (AD77) No. 4 - (AD78) No. 4:

      (AD77) Shield connector - (AD78) Shield connector:

   Is the resistance 1 Ω or less?

   Yes  Go to  5.

   No  Repair or replace the open circuit of harness.

5. CHECK DCM. 

   Perform the inspection according to the diagnosis for telematics system. Refer to PROCEDURE .

   Is the check result OK?

   Yes  Replace the audio or navigation unit. Refer to AUDIO , NAVIGATION BODY .

   No  Replace the DCM. Refer to DATA COMMUNICATION MODULE .