Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
DTC B2256: Data Communication Module Communication Open
DTC detecting condition:
- Detected when a DCM that operates properly is not connected via USB.
- Detected when the DCM is not connected via USB.
Trouble symptom:
DCM linkage function cannot be used.
- CHECK DTC
.
- Using the Subaru Select Monitor, perform the clear memory of [Cockpit Control]. Refer to COMMON (DIAG)>CLEAR MEMORY .
- Turn the ignition switch OFF → ON.
- Read the DTC of [Cockpit Control] using the Subaru Select Monitor. Refer to COCKPIT CONTROL (DIAGNOSTICS)>DIAGNOSTIC TROUBLE CODE (DTC) .
Is DTC B2256 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. - CHECK CONNECTOR
.
Check the harness between the cockpit control module connector and DCM.
Is the check result OK?
Yes : Go to 3.
No : Repair the harness or replace the components.
- CHECK DCM
.
Perform the inspection according to the diagnosis for telematics system. Refer to TELEMATICS SYSTEM (DIAGNOSTICS)>BASIC DIAGNOSTIC PROCEDURE .
Is the check result OK?
Yes : Replace the cockpit control module. Refer to ENTERTAINMENT & MONITORING>COCKPIT DISPLAY .
No : Replace the DCM. Refer to ENTERTAINMENT & MONITORING>DATA COMMUNICATION MODULE .
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.
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