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Home >> Cadillac >> 2021 >> CT4 Sport, 4WD >> Repair and Diagnosis >> External Pages >> Different car >> Section 191 (Data Communications - Diagnostic Information And Procedures (3 Of 3)) >> Diagnostic Information and Procedures >> Scan Tool Does Not Communicate with Vehicle >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different car, the 2022 Cadillac CT4. However, it is still accessible from the selected car via links, so may be relevant.
NOTE:

Use the schematics and connector end views to identify the K56 Serial Data Gateway Module's ground and B+ circuit terminals.

  1. Ignition ON/Vehicle In Service Mode.
  2. Test for less than 4.5 V between each of the CAN 6 serial data circuit terminals listed below and ground:
    • X84 Data Link Connector terminal 6
    • X84 Data Link Connector terminal 14
    • If 4.5 V or greater 
    1. Ignition/Vehicle OFF, disconnect the harness connectors at the K56 Serial Data Gateway Module.
    2. Ignition ON/Vehicle In Service Mode.
    3. Test for less than 1 V between the CAN 6 serial data circuit terminal and ground.
      • If 1 V or greater, repair the short to voltage in the serial data circuit.
      • If less than 1 V, replace the K56 Serial Data Gateway Module.
    • Go to next step: If less than 4.5 V 
  3. 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.
  4. Test for greater than 100 Ω between each of the CAN 6 serial data circuit terminals listed below and ground:
    • X84 Data Link Connector terminal 6
    • X84 Data Link Connector terminal 14
    • If 100 Ω or less 
    1. Disconnect the harness connectors at the K56 Serial Data Gateway Module.
    2. Test for infinite resistance between the CAN 6 serial data circuit terminal and ground.
      • If less than infinite resistance, repair the short to ground in the serial data circuit.
      • If infinite resistance, replace the K56 Serial Data Gateway Module.
    • Go to next step: If greater than 100 Ω 
  5. Test for 110 - 130 Ω between the CAN 6 serial data circuit terminals 6 and 14 at the X84 Data Link Connector.
    • If less than 110 Ω 
    1. Disconnect the harness connectors at the K56 Serial Data Gateway Module.
    2. Test for infinite resistance between the pair of CAN 6 serial data circuit terminals.
      • If less than infinite resistance, repair the short together in the serial data circuits.
      • If infinite resistance, replace the K56 Serial Data Gateway Module.
    • If greater than 130 Ω 
    1. Disconnect the harness connectors at the K56 Serial Data Gateway Module.
    2. Test for less than 2 Ω in each of the CAN 6 serial data circuits end to end between the X84 Data Link Connector 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, replace the K56 Serial Data Gateway Module.
    • Go to next step: If between 110 - 130 Ω 
  6. Ignition ON/Vehicle In Service Mode.
  7. Test for less than 4.5 V between each of the CAN 7 serial data circuit terminals listed below and ground:
    • X84 Data Link Connector terminal 1
    • X84 Data Link Connector terminal 9
    • If 4.5 V or greater 
    1. Ignition/Vehicle OFF, disconnect the harness connectors at the K56 Serial Data Gateway Module.
    2. Ignition ON/Vehicle In Service Mode.
    3. Test for less than 1 V between the CAN 7 serial data circuit terminal and ground.
      • If 1 V or greater, repair the short to voltage in the serial data circuit.
      • If less than 1 V, replace the K56 Serial Data Gateway Module.
    • Go to next step: If less than 4.5 V 
  8. 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.
  9. Test for greater than 100 Ω between each of the CAN 7 serial data circuit terminals listed below and ground:
    • X84 Data Link Connector terminal 1
    • X84 Data Link Connector terminal 9
    • If 100 Ω or less 
    1. Disconnect the harness connectors at the K56 Serial Data Gateway Module.
    2. Test for infinite resistance between the CAN 7 serial data circuit terminal and ground.
      • If less than infinite resistance, repair the short to ground in the serial data circuit.
      • If infinite resistance, replace the K56 Serial Data Gateway Module.
    • Go to next step: If greater than 100 Ω 
    10. NOTE:

    The CAN 7 bus is used for programming by assembly plant only.

  10. Test for 110 - 130 Ω between the CAN 7 serial data circuit terminals 1 and 9 at the X84 Data Link Connector.
    • If less than 110 Ω 
    1. Disconnect the harness connectors at the K56 Serial Data Gateway Module.
    2. Test for infinite resistance between the pair of CAN 7 serial data circuit terminals.
      • If less than infinite resistance, repair the short together in the serial data circuits.
      • If infinite resistance, replace the K56 Serial Data Gateway Module.
    • If greater than 130 Ω 
    1. Disconnect the harness connectors at the K56 Serial Data Gateway Module.
    2. Test for less than 2 Ω in each of the CAN 7 serial data circuits end to end between the X84 Data Link Connector 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, replace the K56 Serial Data Gateway Module.
    • Go to next step: If between 110 - 130 Ω 
  11. Disconnect the harness connectors at the K56 Serial Data Gateway Module.
  12. Ignition ON/Vehicle In Service Mode.
  13. Test for less than 1 V between the Ethernet bus 1 enable signal circuit terminal 8 at the X84 Data Link Connector and ground:
    • If 1 V or greater 

      Repair the short to voltage in the Ethernet bus 1 enable signal circuit.

    • Go to next step: If less than 1 V 
  14. 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.
  15. Test for infinite resistance between the Ethernet bus 1 enable signal circuit terminal 8 at the X84 Data Link Connector and ground:
    • If less than infinite resistance 

      Repair the short to ground in the Ethernet bus 1 enable signal circuit.

    • Go to next step: If infinite resistance 
  16. Test for less than 2 Ω in the Ethernet bus 1 enable signal circuit end to end between the X84 Data Link Connector and the K56 Serial Data Gateway Module.
    • If 2 Ω or greater 

      Repair the open/high resistance in the Ethernet bus 1 enable signal circuit.

    • Go to next step: If less than 2 Ω 
  17. Ignition ON/Vehicle In Service Mode.
  18. Test for less than 1 V between each of the Ethernet 1R serial data circuit terminals listed below and ground:
    • X84 Data Link Connector terminal 3
    • X84 Data Link Connector terminal 11
    • If 1 V or greater 

      Repair the short to voltage in the serial data circuit.

    • Go to next step: If less than 1 V 
  19. 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.
  20. Test for infinite resistance between each of the Ethernet 1R serial data circuit terminals listed below and ground:
    • X84 Data Link Connector terminal 3
    • X84 Data Link Connector terminal 11
    • If less than infinite resistance 

      Repair the short to ground in the serial data circuit.

    • Go to next step: If infinite resistance 
  21. Test for infinite resistance between the Ethernet 1R serial data circuit terminals 3 and 11 at the X84 Data Link Connector.
    • If less than infinite resistance 

      Repair the short together in the serial data circuits.

    • Go to next step: If infinite resistance 
  22. Test for less than 2 Ω in each of the Ethernet 1R serial data circuits end to end between the X84 Data Link Connector and the K56 Serial Data Gateway Module.
    • If 2 Ω or greater 

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

    • Go to next step: If less than 2 Ω 
  23. Ignition ON/Vehicle In Service Mode.
  24. Test for less than 1 V between each of the Ethernet 1T serial data circuit terminals listed below and ground:
    • X84 Data Link Connector terminal 12
    • X84 Data Link Connector terminal 13
    • If 1 V or greater 

      Repair the short to voltage in the serial data circuit.

    • Go to next step: If less than 1 V 
  25. 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.
  26. Test for infinite resistance between each of the Ethernet 1T serial data circuit terminals listed below and ground:
    • X84 Data Link Connector terminal 12
    • X84 Data Link Connector terminal 13
    • If less than infinite resistance 

      Repair the short to ground in the serial data circuit.

    • Go to next step: If infinite resistance 
  27. Test for infinite resistance between the Ethernet 1T serial data circuit terminals 12 and 13 at the X84 Data Link Connector.
    • If less than infinite resistance 

      Repair the short together in the serial data circuits.

    • Go to next step: If infinite resistance 
  28. Test for less than 2 Ω in each of the Ethernet 1T serial data circuits end to end between the X84 Data Link Connector and the K56 Serial Data Gateway Module.
    • If 2 Ω or greater 

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

    • Go to next step: If less than 2 Ω 
  29. Verify a test lamp illuminates between the ground circuit terminal 4 X1 at the K56 Serial Data Gateway Module and B+.
    • If the test lamp does not illuminate 

      Repair the open/high resistance in the ground circuit or ground connection.

    • Go to next step: If the test lamp illuminates 
  30. Ignition ON/Vehicle In Service Mode.
  31. Verify a test lamp illuminates between the B+ circuit terminal 1 X1 at the K56 Serial Data Gateway Module and ground.
    • If the test lamp does not illuminate and the circuit fuse is good 
    1. Test for an open/high resistance in the B+ circuit.
      • If an open/high resistance is found, repair the fault on the circuit.
      • Go to next step: If an open/high resistance is not found
    2. 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. Test for a short to ground in the B+ circuit.
      • If a short to ground is found, repair the fault in the circuit.
      • Go to next step: If a short to ground is not found
    2. Replace the K56 Serial Data Gateway Module.
    • Go to next step: If the test lamp illuminates 
    32. NOTE:

    Connect the scan tool to another vehicle to verify that the scan tool is working properly prior to replacing the K56 Serial Data Gateway Module.

  32. Replace the K56 Serial Data Gateway Module.
  33. Ignition ON/Vehicle In Service Mode.
  34. Verify the scan tool is communicating with vehicle.
    • If the scan tool is not communicating with vehicle 

      Refer to the scan tool user guide.

    • Go to next step: If the scan tool is communicating with vehicle 
  35. All OK.
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