Pinpoint Test AQ: DTC U0256 Or DTC U0255:00

Information and Entertainment System

Pinpoint Tests

Pinpoint Test AQ: DTC U0256 Or DTC U0255:00

Normal Operation
- DTC U0256 (Lost Communication With Front Display Interface Module) - set by the non-navigation Audio Control Module (ACM) when network messages are missing from the Front Display Interface Module (FDIM) over the Medium Speed Controller Area Network (MS-CAN) for greater than 5 seconds with the ignition in the RUN position.
- DTC U0255:00 (Lost Communication With Front Display Interface Module: No Sub Type Information) - set by the Accessory Protocol Interface Module (APIM) when network messages are missing from the FDIM over the MS-CAN for greater than 5 seconds with the ignition in the RUN position.

This pinpoint test is intended to diagnose the following:

- Communication network concern
- ACM
- FDIM
- APIM


PINPOINT TEST AQ: DTC U0256 OR DTC U0255:00

NOTE: Disregard the pinpoint test steps for the APIM if the concern is on a vehicle without the SYNC system.

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AQ1 CHECK THE ACM AND FDIM DTCs

NOTE: If new modules were installed prior to the DTC being set, the module configuration may be incorrectly set during Programmable Module Installation (PMI) or the PMI may not have been carried out.

- Clear the ACM and APIM DTCs.
- Ignition OFF.
- Ignition ON.
- Wait at least 10 seconds.
- Repeat the ACM and APIM self-tests.
- Is DTC U0256 or DTC U0255:00 still present?

Yes
GO to AQ2.

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

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AQ2 VERIFY THE CUSTOMER CONCERN

- Ignition ON.
- Verify that there is an observable symptom present.
- Is an observable symptom present?

Yes
GO to AQ3.

No
The system is operating correctly at this time. The DTC may have been set due to an intermittent fault in the network wiring. CHECK the MS-CAN wiring between the FDIM and the module in question for an intermittent fault.

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AQ3 CHECK THE COMMUNICATION NETWORK

- Ignition ON.
- Carry out the network test using the scan tool.
- Does the FDIM pass the network test?

Yes
GO to AQ4.

No
REFER to Module Communications Network Testing and Inspection.

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AQ4 CHECK FOR BATTERY VOLTAGE OUT-OF-RANGE DTCs

- Carry out the self-test for the following modules:
- ACM
- APIM
- FDIM
- Are any low or high voltage DTCs recorded in any module?

Yes
REFER to DTC Charts. Diagnostic Trouble Code Tests and Associated Procedures

No
INSTALL a new FDIM. REFER to Front Display Interface Module (FDIM) Front Display Interface Module (FDIM). CLEAR the ACM and APIM DTCs. REPEAT the ACM and APIM self-tests.

If DTC U0256 is still present in the ACM, INSTALL a new ACM. REFER to Audio Control Module (ACM) Audio Control Module (ACM). TEST the system for normal operation.

If DTC U0256:00 is still present in the APIM, INSTALL a new APIM. REFER to Accessory Protocol Interface Module (APIM) Accessory Protocol Interface Module (APIM). TEST the system for normal operation.

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