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Home >> Chevrolet >> 2014 >> SS >> Repair and Diagnosis >> Engine Performance >> System >> Data Communication System >> Diagnostic Information and Procedures >> Scan Tool Does Not Communicate with Low Speed GMLAN Device >> Circuit/System Verification
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Circuit/System Verification

NOTE:

Use the schematic to identify the following:

  • Devices the vehicle is equipped with
  • Device and splice pack locations on the low speed GMLAN serial data circuit
  • The low speed GMLAN serial data circuit terminals for each device or splice pack
  1. Attempt to communicate with all devices on the low speed GMLAN serial data circuit. Refer to Data Link References .
  2. Verify which devices are communicating on the low speed GMLAN serial data circuit.
    • If only one device is not communicating 

      Diagnose that device only. Refer to DTC U0100-U02FF .

    • If none of the devices are communicating 
  3. Ignition OFF, all access doors closed, all vehicle systems OFF, all keys at least 3 m (9.8 ft) away from vehicle. Disconnect the scan tool from the X84 Data Link Connector. The following tests will be done at the X84 Data Link Connector. It may take up to 2 minutes for all vehicle systems to power down.
  4. Test for less than 10 Ω between the ground circuit terminal 5 and ground.
    • If 10 Ω or greater 
    1. Ignition OFF.
    2. Test for less than 2 Ω in the ground circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, repair the open/high resistance in the ground connection.
    • If less than 10 Ω 
  5. Ignition ON.
  6. Test for less than 4.5 V between the serial data circuit terminal 1 and ground.
    • If less than 4.5 V 
  7. Ignition OFF, all access doors closed, all vehicle systems OFF, all keys at least 3 m (9.8 ft) away from vehicle. It may take up to 2 minutes for all vehicle systems to power down.
  8. Test for greater than 100 Ω between the serial data circuit terminal 1 and ground.
    • If greater than 100 Ω 
  9. Disconnect the appropriate harness connector at the first splice pack closest in the circuit to the X84 Data Link Connector.
  10. Test for less than 2 Ω between the X84 Data Link Connector's serial data circuit terminal 1 and the splice pack harness connector's serial data input terminal.
    • If 2 Ω or greater 

      Repair the open/high resistance in the serial data circuit.

    • If less than 2 Ω 
  11. Replace the splice pack.
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