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Pinpoint Test Am: FD-Can (Flexible Data Rate Controller Area Network) Bus Off

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  1. Refer to MODULE COMMUNICATIONS NETWORK for schematic and connector information.

    Normal Operation and Fault Conditions 

    The TCM communicates with other vehicles modules over FD-CAN. The TCM will set a DTC when it has not received any messages from other modules on the network for 10 seconds. If the network is down, other modules on the network may set a DTC as well.

    DTC Fault Trigger Conditions 

    DTC Description Fault Trigger Condition
    TCM U0028:00 Vehicle Communication Bus A: No Sub Type Information This DTC illuminates the wrench light in conjunction with U0073.
    TCM U0073:00 Control Module Communication Bus "A" Off: No Sub Type Information This DTC indicates the TCM did not receive any messages from other modules on FD-CAN for 10 seconds or longer. The TCM communicates with the scan tool through FD-CAN, so communication with the scan tool indicates an intermittent fault.

    Possible Sources 

    • Connectors damaged or pushed-out terminals, corrosion, loose wires and missing or damaged seals
    • Circuit open or shorted
    • Communication concern
    • TCM fault

  2. AM1 CHECK FOR FD-CAN (FLEXIBLE DATA RATE CONTROLLER AREA NETWORK) BUS DIAGNOSTIC TROUBLE CODES (DTCS) IN OTHER MODULES

    • Using a diagnostic scan tool, retrieve all continuous memory diagnostic trouble codes (CMDTCs) from all modules.

    Are FD-CAN bus diagnostic trouble codes (DTCs) present in other modules on the network? 

    Yes  There is an intermittent No FD-CAN communication, all modules are not responding concern. REFER to: Controller Area Network (CAN) Module Communications Network .
    No  This indicates a fault that only affects the TCM. GO to  AM2

  3. AM2 INSPECT THE TCM (TRANSMISSION CONTROL MODULE) FD-CAN (FLEXIBLE DATA RATE CONTROLLER AREA NETWORK) CONNECTORS

    • Ignition OFF.

    • Disconnect TCM C1822.

    • Disconnect In-line connector C1282.

    • Using a good light source, inspect both connectors for the following:

      • corrosion (install new connector or terminals - clean module pins)
      • damaged or bent pins - install new terminals/pins
      • pushed-out pins - install new pins as necessary
      • spread terminals - install new terminals as necessary

    Are any connector or pin issues present? 

    Yes  REPAIR any connector or pin issues.
    No  GO to  AM3

  4. AM3 ATTEMPT TO DUPLICATE THE CONCERN

    • Connect TCM C1822.

    • Connect In-line connector C1282.

    • Ignition ON.

    • Using a diagnostic scan tool, clear all diagnostic trouble codes from the TCM.

    • Access the TCM and monitor the VPWR (V) PID

    • Wiggle test the wiring harness between the TCM and splice S162 while monitoring PID VPWR.

    Did the scan tool lose communication with the TCM during the wiggle test? 

    Yes  REPAIR the intermittent circuit fault in the wiring harness.
    No  GO to  AM4

  5. AM4 RECHECK THE TCM (TRANSMISSION CONTROL MODULE) FOR DTC (DIAGNOSTIC TROUBLE CODE) U0028, U0073

    • Road test the vehicle.

    • Using a diagnostic scan tool, carry out the TCM self-test.

    Is DTC U0028 and/or U0073 present? 

    Yes  GO to  AM5
    No  The fault is not present at this time. It might have been caused by a loose or corroded connector, or an intermittent fault condition. ADDRESS the root cause of any connector or pin issues.

  6. AM5 CHECK FOR CORRECT TCM (TRANSMISSION CONTROL MODULE) OPERATION

    • Ignition OFF.

    • Disconnect and inspect the TCM connector.

    • Repair:

      • corrosion (install new connector or terminals - clean module pins)
      • damaged or bent pins - install new terminals/pins
      • pushed-out pins - install new pins as necessary

    • Connect the TCM connector. Make sure it seats and latches correctly.

    • Operate the system and determine if the concern is still present.

    Is the concern still present? 

    Yes  CHECK for an applicable TSB, GSB, SSM, or FSA. If a service bulletin exists for this concern, discontinue this test and follow bulletin instructions. If none address this concern, INSTALL a new TCM. REFER to: Transmission Control Module (TCM) . CARRY OUT the transmission strategy download. REFER to: Transmission Strategy Download .
    No  The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector. ADDRESS the root cause of any connector or pin issues.
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