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.

Ignition OFF, disconnect the connector at the appropriate component:
- B198F = E42R Tail Lamp Assembly - Right
- B1990 = E42L Tail Lamp Assembly - Left
Verify a test lamp illuminates between ground circuit terminal 1 and B+.
- If the test lamp does not illuminate
1. Repair the open/high resistance on the ground circuit or ground connection.
- Go to next step: If the test lamp illuminates
Connect a test lamp between control circuit terminal 5 and ground, ignition on.
Verify the test lamp turns on and off when commanding the appropriate Stop Lamp on and off with a scan tool.
- If the test lamp is always OFF
1. Test the appropriate circuit for a short to ground:
  - E42R Tail Lamp Assembly - Right = Circuit 7541
  - E42L Tail Lamp Assembly - Left = Circuit 7542
  - 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 the appropriate circuit for an open/high resistance:
  - E42R Tail Lamp Assembly - Right = Circuit 7541
  - E42L Tail Lamp Assembly - Left = Circuit 7542
  - 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 K219 Lighting Control Module.
- If the test lamp is always ON
1. Test the appropriate circuit for a short to voltage:
  - E42R Tail Lamp Assembly - Right = Circuit 7541
  - E42L Tail Lamp Assembly - Left = Circuit 7542
  - If a short to voltage is found, repair the fault on the circuit.
  - Go to next step: If a short to voltage is not found.
2. Replace the K219 Lighting Control Module.
- Go to next step: If the test lamp turns ON and OFF
Replace the appropriate stop lamp.