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Home >> Cadillac >> 2021 >> CT4 Sport, 4WD >> Repair and Diagnosis >> External Pages >> Different car >> Section 135 (12 V Starting And Charging - Diagnostic Information And Procedures) >> Diagnostic Information and Procedures >> Stop/Start System Malfunction >> 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.

Stop/Start Switch Malfunction

  1. Ignition OFF, disconnect the X3 electrical connector at the K9 Body Control Module, ignition ON.
  2. Verify the auto stop/start disable indicator on the auto stop/start disable switch is not illuminated.
    • If the auto stop/start disable indicator is illuminated 

      Repair the short to voltage on circuit 1110

    • Go to next step: If the auto stop/start disable indicator is not illuminated 
  3. Test for infinite resistance between signal circuit terminal 23 and ground.
    • If less than infinite resistance 
    1. Test circuit 1111 for a short to ground.
      • If a short to ground is found, repair the fault on the circuit.
      • Go to next step: If a short to ground is not found
    2. Replace the S86 Vehicle Stability Control System Switch.
    • Go to next step: If infinite resistance 
  4. Test for less than infinite resistance between signal circuit terminal 23 and ground while pressing and holding the auto stop/start disable switch.
    • If infinite resistance 
    1. Test circuit 1450 for an open/high resistance.
      • If an open/high resistance is found, repair the fault on the circuit or ground connection.
      • Go to next step: If an open/high resistance is not found
    2. Test circuit 1111 for an open/high resistance.
      • 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
    3. Ignition On Vehicle in Service Mode.
    4. Test Circuit 1111 for a short to voltage.
      • If Short to voltage is found repair the fault on the circuit.
      • Go to next step: If Short to voltage is not found
    5. Replace the S86 Vehicle Stability Control System Switch.
    • Go to next step: If less than infinite resistance 
  5. Connect a 3 A jumper wire between control circuit terminal 15 and B+.
  6. Verify the auto stop/start disable indicator on the auto stop/start disable switch is illuminated.
    • If the auto stop/start disable indicator is not illuminated 
    1. Test circuit 1110 for a short to ground.
      • If a short to ground is found, repair the fault on the circuit.
      • Go to next step: If a short to ground is not found
    2. Test circuit 1110 for an open/high resistance.
      • 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
    3. Replace the S86 Vehicle Stability Control System Switch.
    • Go to next step: If the auto stop/start disable indicator is illuminated 
  7. Replace the K9 Body Control Module.

Stop/Start System Malfunction

    NOTE:
    • Circuit/System Verification must be performed before proceeding with Circuit/System Testing.
    • If the DTC set only as a history DTC, do not replace any components.
  1. Ignition Off, disconnect the connector at the T19 Multifunction Power Supply Converter.
  2. Verify a test lamp illuminates between ground circuit terminal 7 and B+.
    • If the test lamp does not illuminate 

      Repair the open/high resistance on circuit 2550 or the ground connection.

    • Go to next step: If the test lamp illuminates 
  3. Verify a test lamp illuminates between ground circuit terminal 12 and B+.
    • If the test lamp does not illuminate 

      Repair the open/high resistance on circuit 2550 or the ground connection.

    • Go to next step: If the test lamp illuminates 
  4. Verify a test lamp illuminates between B+ circuit terminal 11 and ground.
    • If the test lamp does not illuminate and the circuit fuse is good 
    1. Test circuit 6240 for an open/high resistance.
      • if an open/high resistance is found, repair the fault on the circuit.
      • Go to next step: If an open or 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 circuit 6240 for a short to ground
      • If a short to ground is found, repair the fault on the circuit.
      • Go to next step: If a short to ground is not found
    2. Test circuit 2172 for a short to ground
      • If a short to ground is found, repair the fault on the circuit.
      • Go to next step: If a short to ground is not found
    3. Replace the T19 Multifunction Power Supply Converter.
    • Go to next step: If the test lamp illuminates 
  5. Using the schematics, identify and remove any fuses powered by control circuit 2172.
  6. Test for less than 1 V between control circuit terminal 10 and ground.
    • If 1 or greater 

      Repair the short to voltage on circuit 2172.

    • Go to next step: If less than 1 V 
  7. Ignition OFF.
  8. Test for infinite resistance between control circuit terminal 10 and ground.
    • If less than infinite resistance 

      Repair the short to ground on circuit 2172.

    • Go to next step: If infinite resistance 
  9. Verify a test lamp illuminates between B+ circuit terminal 8 and ground.
    • If the test lamp does not illuminate and the circuit fuse is good 
    1. Test circuit 6340 for an open/high resistance.
      • if an open/high resistance is found, repair the fault on the circuit.
      • Go to next step: If an open or 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 circuit 6340 for a short to ground
      • If a short to ground is found, repair the fault on the circuit.
      • Go to next step: If a short to ground is not found
    2. Test circuit 2173 for a short to ground
      • If a short to ground is found, repair the fault on the circuit.
      • Go to next step: If a short to ground is not found
    3. Replace the T19 Multifunction Power Supply Converter.
    • Go to next step: If the test lamp illuminates 
  10. Using the schematics, identify and remove any fuses powered by control circuit 2173.
  11. Test for less than 1 V between control circuit terminal 9 and ground.
    • If 1 or greater 

      Repair the short to voltage on circuit 2173.

    • Go to next step: If less than 1 V 
  12. Ignition OFF.
  13. Test for infinite resistance between control circuit terminal 9 and ground.
    • If less than infinite resistance 

      Repair the short to ground on circuit 2173.

  14. Ignition ON.
  15. Verify a test lamp illuminates between terminal 4 and ground.
    • If the test lamp does not illuminate 
    1. Test circuit 4320 for an open/high resistance.
      • if an open/high resistance is found, repair the fault on the circuit.
      • Go to next step: If an open or high resistance is not found
    2. Test circuit 4320 for a short to ground
      • If a short to ground is found, repair the fault on the circuit.
      • Go to next step: If a short to ground is not found
    3. Replace the K20 Engine Control Module.
    • Go to next step: If the test lamp turns illuminates 
  16. Ignition Crank.
  17. Verify a test lamp illuminates between terminal 5 and ground while the engine is cranking.
    • If the test lamp does not illuminate 
    1. Test circuit 625 for an open/high resistance.
      • if an open/high resistance is found, repair the fault on the circuit.
      • Go to next step: If an open or high resistance is not found
    2. Test circuit 625 for a short to ground
      • If a short to ground is found, repair the fault on the circuit.
      • Go to next step: If a short to ground is not found
    3. Replace the K20 Engine Control Module.
    • Go to next step: If the test lamp illuminates 
  18. Replace the T19 Multifunction Power Supply Converter.
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