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Circuit/System Testing

WARNING: This page is about a different car, the 2022 Cadillac CT5. However, it is still accessible from the selected car via links, so may be relevant.

DTC B19C4

  1. Ignition OFF, exterior lamps OFF, disconnect the E83 Backup/Rear Fog Lamp.
  2. Connect a test lamp between ground circuit terminal 1 and control circuit terminal 3.
  3. Ignition ON, verify the test lamp turns ON and OFF when commanding the Rear Fog Lamp ON and OFF with the scan tool.
    • If the test lamp is always ON 
    1. Test circuit 122 for a short to voltage
      • If a short to voltage is found, repair the fault.
      • Go to next step: If a short to voltage is not found, replace the K219 Lighting Control Module.
    • If the test lamp turns is always OFF 
    1. Test circuit 2550 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 122 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. Test circuit 122 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
    4. Replace the K219 Lighting Control Module.
    • Go to next step: If the test lamp turns ON and OFF 
  4. Replace the E83 Backup/Rear Fog Lamp.
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