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Home >> Chevrolet >> 2017 >> Sonic Premier, 4D Hatchback, Automatic Trans >> Repair and Diagnosis >> Engine Performance >> System >> Data Communication System >> Diagnostic Information and Procedures >> DTC U007B: Control Module Communication High Speed Extension CAN Bus Off >> Circuit/System Testing >> Testing the Device Circuits
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Testing the Device Circuits

Testing the Device Circuits

  1. 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 2 min for all vehicle systems to power down.
  2. Test for less than 10 Ω between each ground circuit terminal at the device that was just disconnected and ground.
    • If 10 Ω or greater 
    1. Ignition/Vehicle 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 
  3. If equipped, verify a test lamp illuminates between each B+ circuit terminal and ground.
    • If the test lamp does not illuminate and the circuit fuse is good 
    1. Ignition/Vehicle OFF, remove the test lamp.
    2. Test for less than 2 Ω in the B+ circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, verify the fuse is not open and there is voltage at the fuse.
    • If the test lamp does not illuminate and the circuit fuse is open 
    1. Ignition/Vehicle OFF, remove the test lamp.
    2. Test for infinite resistance between the B+ circuit and ground.
      • If less than infinite resistance, repair the short to ground on the circuit.
      • If infinite resistance, replace the disconnected device.
    • If the test lamp illuminates 
  4. Ignition ON/Vehicle In Service Mode.
  5. If equipped, verify a test lamp illuminates between each ignition circuit terminal, which has a fuse in the circuit, and ground.
    • If the test lamp does not illuminate and the circuit fuse is good 
    1. Ignition/Vehicle OFF, remove the test lamp.
    2. Test for less than 2 Ω in the ignition circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, verify the fuse is OK and there is voltage at the fuse.
    • If the test lamp does not illuminate and the circuit fuse is open 
    1. Ignition/Vehicle OFF, remove the test lamp.
    2. Test for infinite resistance between the ignition circuit and ground.
      • If less than infinite resistance, repair the short to ground on the circuit.
      • If infinite resistance, replace the disconnected device.
    • If the test lamp illuminates 
  6. If equipped, verify a test lamp illuminates between each ignition circuit terminal, which is controlled by a control module, and ground.
    • If the test lamp does not illuminate 
    1. Ignition/Vehicle OFF, remove the test lamp, disconnect the harness connectors at the control module that controls the ignition circuit.
    2. Test for infinite resistance between the ignition circuit and ground.
      • If less than infinite resistance, repair the short to ground on the circuit.
      • If infinite resistance
    3. Test for less than 2 Ω in the ignition circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, replace the control module that controls the ignition circuit.
    • If the test lamp illuminates 
  7. Ignition/Vehicle OFF, all access doors closed, all vehicle systems OFF, and all keys at least 3 m (9.8 ft) away from vehicle. Disconnect the harness connectors at the K56 Serial Data Gateway Module. It may take up to 2 min for all vehicle systems to power down.
  8. Test for less than 2 Ω in each of the gateway expansion high speed GMLAN serial data circuits end to end between the non communicating device and the K56 Serial Data Gateway Module.
    • If 2 Ω or greater 

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

    • If less than 2 Ω 
  9. Test for less than 2 Ω in each of the primary high speed GMLAN serial data circuits (circuit numbers 2500 & 2501) end to end between the K56 Serial Data Gateway Module and the appropriate X84 Data Link Connector (DLC) terminals listed below.
    • X84 Data Link Connector high speed GMLAN serial data circuit terminal 6
    • X84 Data Link Connector high speed GMLAN serial data circuit terminal 14
    • If 2 Ω or greater 

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

    • If less than 2 Ω 
  10. Replace the non communicating device that was disconnected.
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