Pinpoint Test AG: DTC U0256 Or DTC U0255:00
Information and Entertainment System
Pinpoint Tests
Pinpoint Test AG: DTC U0256 Or DTC U0255:00
- DTC U0256 (Lost Communication With Front Display Interface Module) - set by the Audio Control Module (ACM) when network messages are missing from the Front Display Interface Module (FDIM) for greater than 5 seconds with the ignition in RUN.
- 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 for greater than 5 seconds with the ignition in RUN.
This pinpoint test is intended to diagnose the following:
- Communication network concern
- ACM
- APIM
- FDIM
PINPOINT TEST AG: 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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AG1 CHECK FOR LOST COMMUNICATION 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.
- 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 or U0255:00 set in any audio system module?
Yes
GO to AG2.
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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AG2 VERIFY THE CUSTOMER CONCERN
- Operate the audio system in radio tuner (AM/FM) mode.
- Is an observable symptom present?
Yes
GO to AG3.
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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AG3 CHECK THE COMMUNICATION NETWORK
- Carry out the network test using the scan tool.
- Does the FDIM pass the network test?
Yes
GO to AG4.
No
REFER to The FDIM Does Not Respond To The Scan Tool in Module Communications Network Testing and Inspection.
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AG4 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. [1][2]Diagnostic Trouble Code Descriptions
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 U0255:00 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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