ATTENTION:
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IMPORTANT - All
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© 2022 Subaru of America, Inc. All rights reserved.

SERVICE BULLETIN
APPLICABILITY:

SUBJECT:

2019 – 23MY Crosstrek & Impreza
2019 – 24MY Forester
2019 – 22MY Ascent

NUMBER: 18-225-22R

Diagnostics Procedure Addition: DTC B2255

DATE:

06/27/22

REVISED:

10/12/23

INTRODUCTION:
This Service Bulletin is to inform you of the diagnosis procedure of the Harman Infotainment System
when DTC B2255 is detected. This update prevents unnecessary replacement of the head unit or USB
cable.
SERVICE PROCEDURE / INFORMATION:
DTC B2255 indicates a communication problem between the DCM and the Head Unit. The trouble
tree below should be followed to prevent misdiagnosis of the head unit or the USB2 cable
NOTE: No diagnosis of B2255 should occur before a FULL SYSTEM SCAN has been completed
and the Telematics system is confirmed to be DTC free. The presence of any Telematics DTCs would
predicate diagnosing and repairing the Telematics fault before continuing the B2255 diagnosis.
Failure to ensure the Telematics system is trouble-free will result in misdiagnosis and unnecessary
part(s) replacement.
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 (DIAGNOSTICS)>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 code)
YES: Go to Step 2: Check Harness (Open Circuit)
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.
In this case, temporary poor contact of connector, temporary open or
short circuit of harness may be the cause.
CAUTION: VEHICLE SERVICING PERFORMED BY UNTRAINED PERSONS COULD
RESULT IN SERIOUS INJURY TO THOSE PERSONS OR TO OTHERS.
Subaru Service Bulletins are intended for use by professional technicians ONLY. They
are written to inform those technicians of conditions that may occur in some vehicles,
or to provide information that could assist in the proper servicing of the vehicle. Properly
trained technicians have the equipment, tools, safety instructions, and know-how to
do the job correctly and safely. If a condition is described, DO NOT assume that this
Service Bulletin applies to your vehicle, or that your vehicle will have that condition.

Subaru of America, Inc. is
ISO 14001 Compliant
ISO 14001 is the international standard for
excellence in Environmental Management
Systems. Please recycle or dispose of
automotive products in a manner that is friendly
to our environment and in accordance with all
local, state and federal laws and regulations.

Continued...
Bulletin Number: 18-225-22R; Revised: 10/12/23

Page 1 of 10

2. CHECK HARNESS (OPEN CIRCUIT).
1. Turn the ignition switch to OFF.
2. Disconnect the battery.
3. Disconnect the audio connector or navigation unit connector.
4. Disconnect the DCM connector.
NOTE: A thorough inspection of the connectors and connector pins should be
performed at this time. This is critical to aid in proper diagnosis and prevent incorrect part replacement. Previous repair history should be reviewed.

5. Using a DVOM, measure the resistance between audio connector or navigation unit
connector and DCM connector.
Connector & terminal
(AD63) No. 1 — (AD59) No. 2:
(AD63) No. 2 — (AD59) No. 3:
(AD63) No. 3 — (AD59) No. 1:
(AD63) No. 4 — (AD59) No. 4:
(AD63) Shield connector — (AD59) Shield connector:
Is the resistance 1 Ω or less?
YES: Go to Step 3: Check Cable
NO: Repair or replace the open circuit of harness.

3. CHECK CABLE.
1. Visually inspect the USB jumper harness between the DCM and the Head Unit.
You are looking for chaffing or piercing of the harness that may provide an unexpected
short to ground or power when it is installed, and the dashboard is assembled.
Was harness damage found during the visual inspection?
YES: Repair or replace the open circuit of harness.
NO: Go to Step 4: Check USB Jumper Harness (Internal Short)

Continued...
Bulletin Number: 18-225-22R; Revised: 10/12/23

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4. CHECK USB JUMPER HARNESS (INTERNAL SHORT).
1. With the USB harness disconnected on both end and removed from the dash if
necessary.

2. Using a DVOM, measure the resistance between Head Unit connector as detailed
below.

Connector & terminal
(AD63) No. 1 (+) — 2, 3, and 4:
(AD63) No. 2 (+) — 3 and 4:
(AD63) No. 3 (+) — 4:

Is the resistance 1 MΩ or more?
YES: Go to Step 5: Check DCM
NO: Repair or replace the open circuit of harness.

5. CHECK DCM
1. Connect the DCM.
2. Connect the audio connector or navigation unit connector.
3. Connect the battery.
NOTE: Failure to perform the proceeding order of operations for reconnecting
the appropriate connectors & battery, could result in certain functions not operating as designed.

4.Perform the inspection according to the diagnosis for the telematics system. Ref. to
TELEMATICS SYSTEM (DIAGNOSTIC) > Basic Diagnostic Procedure.
Is the Telematics System Check, OK?
YES: Replace the audio of navigation unit. Ref. to ENTERTAINMENT & MONITORING > AUDIO
NO: Repair the DCM. Ref. to ENTERTAINMENT AND MONITORING > DATA COMMUNICATION MODULE.

Continued...
Bulletin Number: 18-225-22R; Revised: 10/12/23

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APPENDIX INFORMATION
USB CONNECTION OVERVIEW

COMMON DIAGNOSTIC > Clear memory
Operation
1. On [Start] screen, select [Diagnosis].
2. On [Vehicle selection] screen, input the target vehicle information and select [OK].
3. On [Main Menu] screen, select [Each System].
4. On [Select System] screen, select the corresponding system and select [Enter].
5. On [Select Function] screen, select [DTC].
6. On [DTC] screen, select [Clear memory].
•

For detailed operation procedures, refer to “Help” of application.

•

When using the Subaru Select Monitor, turn the ignition switch to ON.

•

Sub screen may appear in the system selection display. In that case, select appropriate
items in accordance with the contents of the display.

•

When the clear memory is performed, diagnostic code (DTC) and freeze frame data
(FFD) necessary in diagnosis will also be deleted.

•

Before performing the clear memory, be sure to save the diagnostic code (DTC) and
freeze frame data (FFD) stored in the module.

•

Initial diagnosis of electronic throttle control is performed after memory clearance.
Wait for 10 seconds or more after turning the ignition switch to ON, and then start the
engine.
Continued...

Bulletin Number: 18-225-22R; Revised: 10/12/23

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COMMON DIAGNOSTIC > Diagnostic Trouble Code (DTC)
Operation
1. On [Start] screen, select [Diagnosis].
2. On [Vehicle selection] screen, input the target vehicle information and select [OK].
3. On [Main Menu] screen, select [Each System].
4. On [Select System] screen, select the corresponding system and select [Enter].
5. On [Select Function] screen, select [DTC].
•

For detailed operation procedures, refer to “Help” of application.

•

When using the Subaru Select Monitor, turn the ignition switch to ON.

•

Sub screen may appear in the system selection display. In that case, select appropriate
items in accordance with the contents of the display.

•

Current code is a diagnostic code displayed when the system is judging the current
code. However, if a DTC is recorded due to poor contact etc., the code remains
displayed as current code during the drive cycle even after the poor contact has
resolved.

•

History code is a diagnostic code recorded when the current code is not detected but
the system has detected a malfunction in the past. When the current code is recorded,
it is also recorded to the history code at the same time.

TELEMATICS SYSTEM (DIAGNOSTICS) > General Description
1. BASIC INSPECTION
Before performing the diagnosis, check the following items which may affect the problems relating to the
telematics system.
1. Check the 12V under the hood battery.
2. Check the relay and fuse condition.
3. Check the DCM harness and connectors are installed and firmly seated.
4. Verify DCM ground from terminal A14 to chassis ground.

Continued...
Bulletin Number: 18-225-22R; Revised: 10/12/23

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TELEMATICS SYSTEM (DIAGNOSTICS) > Diagnostic Procedure for Subaru Select Monitor
Communication.
When communication with DCM is impossible
Detecting condition:
Defective harness connector
Power supply circuit malfunction
Defective DCM
Defective CAN communication circuit
Defective Subaru Select Monitor
Trouble symptom:
Communication is impossible between DCM and Subaru Select Monitor.
Please refer to the appropriate STIS manual of the same name for more detailed diagnostic
information.
ENTERTAINMENT & MONITORING > AUDIO
1. Disconnect the ground terminal from the battery sensor.
2. Remove the grille ventilation assembly center.
3. Remove the switch assembly hazard or upper center panel
4. Remove the audio assembly.
(1) Remove the screws.
(2) Release the clips and disconnect the connector, and then remove the audio assembly.
For models with telematics, the data communication module is attached on the upper side of the
audio assembly.
5. Remove the backup unit.
6. Remove the data communication module.
7. Remove the audio bracket.
(1) Remove the screws, and then remove the audio bracket.
Remove the screws on LH side in the same procedure as on the RH side.

Continued...
Bulletin Number: 18-225-22R; Revised: 10/12/23

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ENTERTAINMENT & MONTORING > DATA COMMUNICATION MODULE
DATA COMMUNICATION MODULE
1. Disconnect the ground terminal from battery sensor.
For the hybrid model, disconnect the battery negative terminal.
2. Remove the grille assembly - CTR ventilation.
3. Remove the audio assembly or navigation assembly.
4. Remove the data communication module.
(1) Disconnect the cable connected to the audio assembly.
(2) Remove the screws and remove the data communication module.
Do not drop or apply any impact to the data communication module.
Remove the screws on LH side in the same procedure as on the RH side.

LED illumination status list

Continued...
Bulletin Number: 18-225-22R; Revised: 10/12/23

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Telematics Questionnaire

Continued...
Bulletin Number: 18-225-22R; Revised: 10/12/23

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Telematics System (Diagnostics) > Basic Diagnostic Procedure.

1. Perform Customer Interview
1. Ask the customer when and how the trouble occurred using the interview check list.
Ref. to TELEMATICS SYSTEM (DIAGNOSTICS) > Check List for Interview
Did you interview the customer?
YES: Go to Step 2: Perform Basic Inspection
NO: Perform the Interview and proceed to step 2.

2. Perform Basic Inspection
1. Perform Telematics Basic Inspection. Ref. to TELEMATICS SYSTEM
(DIAGNOSTICS) > GENERAL DESCRIPTION > INSPECTION
Are the basic inspection results as expected?
YES: Go to Step 3 Check SSM4 Communication.
NO: Repair or Replace any faulty items found in the Telematics System Basic
Inspection, then proceed to step 3.

3. CHECK Subaru Select Monitor Communication.
1. Connect the Subaru Select Monitor.
2. Turn the ignition switch to ON.
3. Configure the SSM4 for the vehicle.
4. Select Telematics.
Is Communication with the DCM possible?
YES: Go to Step 4: Check DTC
NO: Check the communication circuit. Ref. to TELEMATICS SYSTEM
(DIAGNOSTICS) > Diagnostic Procedure for Subaru Select Monitor
Communication.

Continued...
Bulletin Number: 18-225-22R; Revised: 10/12/23

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4. CHECK DTC.
1. Read the Telematics DTC using the Subaru Select Monitor. Ref. to TELEMATICS
SYSTEM (DIAGNOSTICS)>Diagnostic Trouble Code (DTC)

If DTC is detected, only RED LED will illuminate. For details, refer to LED
illumination status list.
Are any DTCs? (CURRENT MALFUNCTION)
YES: Record the DTC, time stamp and freeze frame data, then proceed to step 5:
Perform Diagnosis.
NO: Finish Telematics Diagnosis. Test iButton and remote services operation
before releasing to the customer.

5. Perform Diagnosis.
1. Perform the diagnosis for the displayed DTCs.
2. Repair or replace the cause of trouble.
3. Using the Subaru Select Monitor, perform the clear memory of [Telematics].
4. Read the DTC of [Telematics] using the Subaru Select Monitor.
Are any Telematics DTCs displayed? (Current malfunction)
YES: Go to Step 5: Perform Diagnosis. Repeat step 5 until no telematics DTCs are
present.
NO: Finish Telematics Diagnosis. Test iButton and remote services operation
before releasing to the customer.

IMPORTANT REMINDERS:
•

SOA strongly discourages the printing and/or local storage of service information as previously
released information and electronic publications may be updated at any time.

•

Always check for any open recalls or campaigns anytime a vehicle is in for servicing.

•

Always refer to STIS for the latest service information before performing any repairs.

Bulletin Number: 18-225-22R; Revised: 10/12/23

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