U0256

Information and Entertainment System

Pinpoint Test AX: DTC U0256:00

- DTC U0256:00 (Lost Communication With Front Controls Interface Module: No Sub Type Information)- set by the Audio Control Module (ACM) or the Accessory Protocol Interface Module (APIM) when network messages are missing from the Front Controls Interface Module (FCIM) over the Medium Speed Controller Area Network (MS-CAN) for greater than 5 seconds with the ignition in RUN.

This pinpoint test is intended to diagnose the following:

- Communication network concern

- ACM (Audio Control Module)

- APIM (Accessory Protocol Interface Module)

- FCIM (Front Controls Interface Module)

PINPOINT TEST AX : DTC U0256:00

AX1 CHECK FOR LOST COMMUNICATION DTCs

- Ignition ON.

- Clear continuous DTCs from all modules.

- Ignition OFF.

- Ignition ON.

- Wait at least 10 seconds.

- Retrieve all continuous DTCs from all modules.

Is DTC U0256:00 set in an audio system module?

Yes
GO to AX2.

No
The system is operating correctly at this time. The DTC may have been set due to an intermittent fault in the network wiring.

AX2 CHECK FOR BATTERY VOLTAGE OUT-OF-RANGE DTCs

- Carry out the self-test for the following modules:
- ACM (Audio Control Module)

- APIM (Accessory Protocol Interface Module)

- FCIM (Front Controls Interface Module)

Are any low or high voltage DTCs recorded in any module?

Yes
REFER to DTC Charts. Accessories and Optional Equipment

No
GO to AX3.

AX3 CHECK FOR DTC U0256:00 SET IN MULTIPLE MODULES

- Review the recorded results from the self-test.

Is DTC U0256:00 present in both the ACM (Audio Control Module) and the APIM (Accessory Protocol Interface Module)?

Yes
GO to AX4.

No
If there is an observable symptom, REFER to the appropriate Symptom Chart. Symptom Related Diagnostic Procedures

If there is no observable symptom, CHECK the MS-CAN (Medium Speed Controller Area Network) wiring between the ACM (Audio Control Module) and the module in question for an intermittent fault.

AX4 CHECK FOR CORRECT APIM (Accessory Protocol Interface Module) OPERATION

- Ignition OFF.

- Disconnect the APIM (Accessory Protocol Interface Module) connector.

- Check for:
- corrosion

- damaged pins

- pushed-out pins


- Connect the APIM (Accessory Protocol Interface Module) connector and make sure it seats correctly.

- Wait 2 minutes for the APIM (Accessory Protocol Interface Module) to re-initialize.

- Operate the system and verify the concern is still present.

Is the concern still present?

Yes
INSTALL a new APIM (Accessory Protocol Interface Module). REFER to Accessory Protocol Interface Module (APIM) . TEST the system for normal operation.

No
The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector.