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Home >> Chevrolet >> 2019 >> Express 2500 Base, Van Cargo Extended, 2.8L Eng VIN 1 >> Repair and Diagnosis >> Engine Performance >> System >> Data Communications System >> Diagnostic Information and Procedures >> DTC U0077 >> Circuit/System Verification
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Circuit/System Verification

  1. Ignition ON/Vehicle In Service Mode.
  2. Attempt to communicate with all devices on the chassis high speed GMLAN serial data circuit. Refer to Data Link References  to determine how many devices should be communicating on this bus.
  3. Verify that all chassis high speed GMLAN devices are communicating.
    • If only one device is not communicating 

      Refer to Circuit/System Testing - Testing the Device Circuits.

    • If two or more devices are not communicating 

      Refer to Circuit/System Testing - Serial Data Starting Point.

    • Go to next step: If all devices are communicating 
  4. All OK.
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