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Home >> Cadillac >> 2017 >> CT6 Plug-In >> Repair and Diagnosis (Single Page) >> Engine Performance >> System >> Data Communication System - DTC B1000 To DTC U1818 >> Diagnostic Information and Procedures >> DTC P23A9: Communication Fault - Forced Engine Shutdown >> Circuit/System Verification
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Circuit/System Verification

  1. Ignition ON/Vehicle In Service Mode.
  2. Verify that no other DTCs are set.
    • If none of the DTCs are set 
  3. Verify that all high speed GMLAN devices are communicating.
    • If only one high speed GMLAN device is not communicating 

      Refer to DTC U0100-U02FF  to diagnose that device.

    • If all high speed GMLAN devices are communicating 
  4. Ignition/Vehicle OFF, all access doors closed, all vehicle systems OFF and all keys at least 3 m (9.8 ft) away from vehicle. It may take up to 10 min for all vehicle systems to power down.
  5. Ignition ON/Vehicle In Service Mode.
  6. Clear the DTC.
  7. Verify that the DTC does not reset.
    • If the DTC resets 

      Replace the K20 Engine Control Module.

    • If the DTC does not reset 
  8. All OK.
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