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Home >> Cadillac >> 2021 >> CT4 Sport, RWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 189 (Data Communications - Diagnostic Information And Procedures (1 Of 3)) >> Diagnostic Information and Procedures >> DTC U0100 - U02FF (Using Network Communication Status) >> Circuit/System Verification

Circuit/System Verification

WARNING: This page is about a different car, the 2022 Cadillac CT4. However, it is still accessible from the selected car via links, so may be relevant.
NOTE:

For vehicles not equipped with K29F Front Seat Heater Control Module, K29FV Front Seat Heater Vent Control Module, K29R Rear Seat Heater Control Module, or K32 Heated Steering Wheel Module:

  • Ignore DTC U0208 if equipped with RPO 00V
  • Ignore DTC U0229 if equipped with RPO 00G
  • Ignore DTC U0247 if equipped with RPO 00R
  1. Ignition ON/Vehicle In Service Mode.
  2. Refer to Control Module U Code List , and Data Link References to determine the device that is not communicating and its communication protocol.
  3. Verify the non communicating device is not a LIN device.
    • If the device is a LIN device 

      Refer to Circuit/System Testing - Testing a LIN Device  .

    • Go to next step: If the device is not a LIN device 
  4. Ignition/Vehicle OFF, access the Network Communication Status application in scan tool under Vehicle Diagnostics > Vehicle Communication Diagnostics > Network Communication Status.
  5. Verify one or more CAN devices are not communicating. Refer to Network Communication Status to determine the CAN devices that are not communicating.
    • If only one CAN device is not communicating 

      Refer to Circuit/System Testing - Testing a CAN Device  . The possible fault can be device's ground, power, or an open in the CAN serial data circuit between that non communicating device and the K56 Serial Data Gateway Module.

    • If two or more CAN devices are not communicating, but not all 

      Refer to Circuit/System Testing - Testing a CAN Device  . The possible fault can be an open in the CAN serial data circuit at the non communicating device closet to the K56 Serial Data Gateway Module. Use the schematic for CAN bus being tested to determine the non communicating device closest to the K56 Serial Data Gateway Module.

    • If all devices are not communicating 

      Refer to Circuit/System Testing - Testing a CAN Device  . One of the following faults can occur:

    • A short to voltage in a CAN serial data circuit.
    • A short to ground in a CAN serial data circuit.
    • A short together between CAN serial data circuits.
    • An open/high resistance in a CAN serial data circuit between the K56 Serial Data Gateway Module and the closet non communicating device if the K56 Serial Data Gateway Module is at one end of the bus. Use the schematic for CAN bus being tested to determine the non communicating device closest to the K56 Serial Data Gateway Module.
    • Go to next step: If all CAN devices are communicating 
  6. A fault is currently not present and may be an intermittent condition.
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