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Home >> Chevrolet >> 2019 >> Traverse Premier, FWD >> Repair and Diagnosis >> Engine Performance >> System >> Data Communications - Diagnostic Information And Procedures >> Diagnostic Information and Procedures >> Scan Tool Does Not Communicate with Object High Speed GMLAN Device >> Circuit/System Testing
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Circuit/System Testing

NOTE:

Some devices with an internal terminating resistor have a loop in the harness that connects the internal terminating resistor to the serial data circuit. When wired this way, test these loop circuits for the appropriate failure mode short to voltage, short to ground, or open/high resistance prior to replacing the device for each of the following tests. Each device may need to be disconnected to isolate a circuit fault. Use the wiring schematics and connector end views to identify the following:

  • Object high speed GMLAN devices and terminating resistors the vehicle is equipped with
  • Device locations on the object high speed GMLAN serial data circuits
  • Each device's ground, B+, ignition, and object high speed GMLAN serial data circuit terminals

Serial Data Starting Point

  1. Ignition/Vehicle OFF, disconnect the harness connectors with the object high speed GMLAN serial data circuits (circuit numbers 3811 & 3813) at an easily accessible device that is not communicating.
  2. Ignition ON/Vehicle In Service Mode.
  3. Test for less than 4.5 V between each of the object high speed GMLAN serial data circuit terminals at the device connectors that was just disconnected and ground.
    • If 4.5 V or greater 

      Refer to Testing the Serial Data Circuits for a Short to Voltage.

    • Go to next step: If less than 4.5 V 
  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. Test for greater than 100 Ω between each of the object high speed GMLAN serial data circuit terminals at the device connectors that was just disconnected and ground.
    • If 100 Ω or less 

      Refer to Testing the Serial Data Circuits for a Short to Ground.

    • Go to next step: If greater than 100 Ω 
  6. Test for 110 - 130 Ω between each pair of the object high speed GMLAN serial data circuit terminals at the device connectors that was just disconnected.
    • If less than 110 Ω 

      Refer to Testing the Serial Data Circuits for a Short between the Circuits.

    • If greater than 130 Ω 

      Refer to Testing the Serial Data Circuits for an Open/High Resistance.

    • Go to next step: If between 110 - 130 Ω 
  7. Replace the device that was just disconnected.

Testing the Serial Data Circuits for a Short to Voltage

  1. Ignition/Vehicle OFF, disconnect the harness connectors with the object high speed GMLAN serial data circuits at another device, in the direction of the circuit shorted to voltage.
  2. Ignition ON/Vehicle In Service Mode.
  3. Test for greater than 4.5 V between each of the object high speed GMLAN serial data circuit terminals at the device connectors that was just disconnected and ground.
    • If each serial data circuit is 4.5 V or less 

      Replace the device that was disconnected.

    • Go to next step: If any serial data circuit is greater than 4.5 V 
  4. Repeat step 1 until one of the following conditions are isolated:
    • A short to voltage on the serial data circuit between two devices or splice packs, if equipped.
    • A short to voltage on the serial data circuit between a device and a terminating resistor.

Testing the Serial Data Circuits for a Short to Ground

  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 10 min for all vehicle systems to power down.
  2. Disconnect the harness connectors with the object high speed GMLAN serial data circuits at another device, in the direction of the circuit shorted to ground.
  3. Test for greater than 100 Ω between each of the object high speed GMLAN serial data circuit terminals at the device connectors that was just disconnected and ground.
    • If each serial data circuit is 100 Ω or greater 

      Replace the device that was disconnected.

    • Go to next step: If any serial data circuit is less than 100 Ω 
  4. Repeat step 1 until one of the following conditions are isolated:
    • A short to ground on the serial data circuit between two devices or splice packs, if equipped.
    • A short to ground on the serial data circuit between a device and a terminating resistor.

Testing the Serial Data Circuits for a Short between the 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 10 min for all vehicle systems to power down.
  2. Connect the harness connectors at the device that was disconnected.
  3. Disconnect the harness connectors with the object high speed GMLAN serial data circuits at another device, in the direction of the circuit shorted together.
  4. Test for greater than 110 Ω between each pair of the object high speed GMLAN serial data circuit terminals at the device connectors that was just disconnected.
    • If each pair of serial data circuits is 110 Ω or greater 

      Replace the device that was disconnected.

    • Go to next step: If any pair of serial data circuits is less than 110 Ω 
  5. Repeat step 1 until one of the following conditions are isolated:
    • Serial data circuits shorted together between two devices or splice packs, if equipped.
    • Serial data circuits shorted together between a device and a terminating resistor.
    • A shorted terminating resistor.

Testing the Serial Data Circuits for an Open/High Resistance

  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 10 min for all vehicle systems to power down.
  2. Connect the harness connectors at the device that was disconnected.
  3. Disconnect the harness connectors with the object high speed GMLAN serial data circuits at another device, in the direction of the circuit with the open/high resistance.
  4. Test for less than 130 Ω between each pair of the object high speed GMLAN serial data circuit terminals at the device connectors that was just disconnected.
    • If each pair of serial data circuits is 130 Ω or less 

      Replace the device that was disconnected.

    • Go to next step: If any pair of serial data circuits is greater than 130 Ω 
  5. Repeat step 1 until one of the following conditions are isolated:
    • An open/high resistance on the serial data circuit between two devices or splice packs, if equipped.
    • An open/high resistance on the serial data circuit between a device and a terminating resistor.
    • An open/high resistance terminating resistor.

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. Disconnect the harness connectors at an object high speed GMLAN device that is not communicating. It may take up to 10 min for all vehicle systems to power down.
  2. Test for less than 10 Ω between each of the ground circuit terminals 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.
    • Go to next step: If less than 10 Ω 
  3. Ignition ON/Vehicle In Service Mode.
  4. If equipped, verify a test lamp illuminates between each of the B+ circuit terminals 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. Refer to Power Mode Mismatch .
    • 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.
    • Go to next step: If the test lamp illuminates 
  5. If equipped, verify a test lamp illuminates between each of the ignition circuit terminals, 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. Refer to Power Mode Mismatch .
    • 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.
    • Go to next step: If the test lamp illuminates 
  6. If equipped, verify a test lamp illuminates between each of the ignition circuit terminals, 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 and all devices that share the same 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.
      • Go to next step: 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.
      • Go to next step: If less than 2 Ω
    4. Reconnect the control module that controls the ignition circuit, ignition ON/Vehicle In Service Mode.
    5. Verify a test lamp illuminates between the ignition circuit terminal and ground.
      • If the test lamp does not illuminate, replace the control module that controls the ignition circuit.
      • Go to next step: If the test lamp illuminates
    6. Ignition/Vehicle OFF, reconnect the first device that shares the same ignition circuit, ignition ON/Vehicle In Service Mode.
    7. Verify a test lamp illuminates between the ignition circuit terminal and ground.
      • If the test lamp does not illuminate, replace the device that was just connected.
      • If the test lamp illuminates and there are more devices to connect, connect the next device and repeat step 6.7 until there are no more devices to connect.
    • Go to next step: If the test lamp illuminates 
  7. If equipped, verify a test lamp illuminates between the accessory wake-up serial data circuit terminal and ground.
    • If the test lamp does not illuminate 
    1. Ignition/Vehicle OFF, remove the test lamp, disconnect the harness connectors at the K9 Body Control Module.
    2. Test for less than 2 Ω in the accessory wake-up serial data circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, replace the K9 Body Control Module.
    • Go to next step: If the test lamp illuminates 
  8. If equipped, verify a test lamp illuminates between the serial data communication enable circuit terminal and ground.
    • If the test lamp does not illuminate 
    1. Ignition/Vehicle OFF, remove the test lamp, disconnect the harness connectors at the K9 Body Control Module.
    2. Test for less than 2 Ω in the serial data communication enable circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, replace the K9 Body Control Module.
    • Go to next step: If the test lamp illuminates 
  9. 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.
  10. Disconnect the harness connector at an object high speed GMLAN device that is still communicating and closest to the non communicating device.
  11. Test for less than 2 Ω in each of the object high speed GMLAN serial data circuits end to end between the non communicating device and the device that was just disconnected.
    • If 2 Ω or greater 

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

    • Go to next step: If less than 2 Ω 
  12. Replace the non communicating device.
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