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Home >> Chevrolet >> 2021 >> Traverse L >> Repair and Diagnosis >> Engine Performance >> System >> Data Communications - Diagnostic Information And Procedures >> Diagnostic Information and Procedures >> DTC U1500-U15FF >> Circuit/System Testing
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Circuit/System Testing

NOTE:
  • A DTC in U1501-U150F range is normally used to indicate a LIN bus off. If a DTC in U1501-U150F range is set by itself, use the LIN schematics for the device setting this DTC to identify the LIN slave device to diagnose it.
  • For some vehicles, both headlamps may be connected to the same LIN circuit through a splice. Or both LIN circuits to the headlamps may be internally connected at the connector of the K26 Headlamp Control Module (or K28 Headlamp Leveling Control Module). A short in one headlamp or its LIN circuit may cause no communication to both headlamps. Ensure to diagnose both LIN circuits and headlamps prior to replacing any headlamp.
  • Use the schematic to identify the following:
    • The master control module and the LIN devices on the same LIN serial data circuit
    • The master control module's LIN serial data circuit terminal and the LIN device's B+, ignition, ground, and LIN serial data circuit terminals
  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 a LIN 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 ground circuit terminal 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 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 in the circuit.
      • If infinite resistance, replace the disconnected LIN device.
    • Go to next step: If the test lamp illuminates 
  5. If equipped, verify a test lamp illuminates between each ignition 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 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 in the circuit.
      • If infinite resistance, replace the disconnected LIN device.
    • Go to next step: 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 and all devices that share the same ignition circuit.
    2. Test for infinite resistance between the ignition circuit terminal and ground.
      • If less than infinite resistance, repair the short to ground in 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.
    5. Ignition ON/Vehicle In Service Mode.
    6. 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
    7. Ignition/Vehicle OFF, reconnect the first device that shares the same ignition circuit.
    8. Ignition ON/Vehicle In Service Mode.
    9. 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 6.9 until there are no more devices to connect.
    • Go to next step: If the test lamp illuminates 
  7. Ignition/Vehicle OFF, disconnect all LIN devices that share the same LIN serial data circuit.
  8. Ignition ON/Vehicle In Service Mode.
    9. NOTE:

    For accurate voltage reading, disconnect the battery charger prior to performing the following test step.

  9. Test for 3.5-12 V between the LIN serial data circuit terminal and ground.
    • If less than 3.5 V 
    1. Ignition/Vehicle OFF, disconnect the harness connectors at the control module setting the DTC.
    2. Test for infinite resistance between the LIN serial data circuit terminal and ground.
      • If less than infinite resistance, repair the short to ground in the circuit.
      • Go to next step: If infinite resistance
    3. Test for less than 2 Ω in the LIN serial data 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. Replace the control module that sets the DTC.
    • If greater than 12 V 
    1. Ignition/Vehicle OFF, disconnect the harness connectors at the control module setting the DTC.
    2. Ignition ON/Vehicle In Service Mode.
    3. Test for less than 1 V between the LIN serial data circuit terminal and ground.
      • If 1 V or greater, repair the short to voltage in the circuit.
      • Go to next step: If less than 1 V
    4. Replace the control module that sets the DTC.
    • Go to next step: If between 3.5-12 V 
  10. Verify how many LIN devices are connected to this LIN circuit.
    • If there is only one LIN device 
    1. Ignition/Vehicle OFF, inspect both harness and component connectors for contamination, corrosion, and terminal tension.
    2. Reconnect the harness connectors at the LIN device. Verify all connectors/terminals are fully seated.
    3. Ignition ON/Vehicle In Service Mode.
    4. Verify the DTC is not set again.
      • If the DTC is set, replace the LIN device that is not communicating.
      • Go to next step: If the DTC is not set
    5. A fault is currently not present and may be an intermittent condition.
    • Go to next step: If there are two or more LIN devices 
  11. Ignition/Vehicle OFF, disconnect the harness connectors at the control module setting the DTC.
  12. Reconnect the harness connectors at the first LIN device.
  13. Ignition ON/Vehicle In Service Mode.
  14. Test for 3.5-12 V between the LIN serial data circuit terminal at the control module setting the DTC and ground.
    • If less than 3.5 V or greater than 12 V 

      Replace the LIN device that was just connected.

    • Go to next step: If between 3.5-12 V 
  15. Ignition/Vehicle OFF, reconnect the harness connectors at another LIN device.
  16. Ignition ON/Vehicle In Service Mode.
  17. Test for 3.5-12 V between the LIN serial data circuit terminal at the control module setting the DTC and ground.
    • If less than 3.5 V or greater than 12 V 

      Replace the LIN device that was just connected.

    • Go to next step: If between 3.5-12 V 
  18. Repeat steps 15-17 for the remaining LIN devices until a faulty LIN device is identified. If there is no faulty LIN device, replace the LIN device that is not communicating.
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