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Home >> GMC >> 2018 >> Acadia Denali, FWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 274 (Lighting System - DTC B3891 To DTC C0297 And Diagnostic Information And Procedures) >> Diagnostic Information and Procedures >> Park, License, and/or Tail Lamps Malfunction >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different car, the 2017 Cadillac ATS. However, it is still accessible from the selected car via links, so may be relevant.

Turn Signal/Multifunction Switch Malfunction

  1. Ignition OFF, scan tool disconnected, all doors closed, all accessories OFF, open and close drivers door, disconnect the harness connector at the S78 Turn Signal/Multifunction Switch. It may take up to 2 min for all vehicle systems to power down.
  2. Test for less than 10 Ω between the ground circuit terminal 6 and ground.
    • If 10 Ω or greater 
    1. Ignition 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.
    • If less than 10 Ω 
  3. Ignition ON.
  4. Verify the scan tool Park Lamps Switch parameter is Inactive.
    • If not Inactive 
    1. Ignition OFF, disconnect the X1 harness connector at the K9 Body Control Module.
    2. Test for infinite resistance between the signal circuit terminal 7 and ground.
      • If less than infinite resistance, repair the short to ground on the circuit.
      • If infinite resistance, replace the K9 Body Control Module.
    • If Inactive 
  5. Install a 3 A fused jumper wire between the signal circuit terminal 7 and ground.
  6. Verify the scan tool Park Lamps Switch parameter is Active.
    • If not Active 
    1. Ignition OFF, disconnect the X1 harness connector at the K9 Body Control Module, ignition ON.
    2. Test for less than 1 V between the signal circuit terminal 7 and ground.
      • If 1 V or greater, repair the short to voltage on the circuit.
      • If less than 1 V
    3. Test for less than 2 Ω in the signal circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, replace the K9 Body Control Module.
    • If Active 
  7. Test or replace the S78 Turn Signal/Multifunction Switch.

Park Lamps Malfunction - Front Upper and Lower LED's

  1. Ignition OFF, exterior lamps OFF, disconnect the harness connector at the appropriate E4A Park/Daytime Running Lamp. It may take up to 2 min for all vehicle systems to power down.
  2. Test for less than 15 Ω between the appropriate ground circuit terminal listed below and ground.
    • E4AC Park/Daytime Running Lamp - Left terminal 2
    • E4AD Park/Daytime Running Lamp - Right terminal 2
    • E4AL Park/Daytime Running Lamp - Left Lower terminal A
    • E4AM Park/Daytime Running Lamp - Right Lower terminal A
    • If 15 Ω or greater 
    1. Ignition 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.
    • If less than 15 Ω 
  3. Connect a test lamp between the appropriate control circuit terminal listed below and ground, ignition ON.
    • E4AC Park/Daytime Running Lamp - Left terminal 4
    • E4AD Park/Daytime Running Lamp - Right terminal 4
    • E4AL Park/Daytime Running Lamp - Left Lower terminal B
    • E4AM Park/Daytime Running Lamp - Right Lower terminal B
  4. Verify the test lamp turns ON and OFF when commanding the appropriate Front Park Lamp/Daytime Running Lamp ON and OFF with a scan tool.
    • If the test lamp is always OFF 
    1. Ignition OFF, disconnect the appropriate harness connector listed below at the K9 Body Control Module.
      • X4 - park/daytime running lamp - left and right upper
      • X5 - park/daytime running lamp - right lower
    2. Test for infinite resistance between the control circuit and ground.
      • If less than infinite resistance, repair the short to ground on the circuit.
      • If infinite resistance
    3. Test for less than 2 Ω in the control circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, replace the K9 Body Control Module.
    • If the test lamp is always ON 
    1. Ignition OFF, disconnect the appropriate harness connector listed below at the K9 Body Control Module, ignition ON.
      • X4 - park/daytime running lamp - left and right upper
      • X5 - park/daytime running lamp - right lower
    2. Test for less than 1 V between the control circuit terminal and ground.
      • If 1 V or greater, repair the short to voltage on the circuit.
      • If less than 1 V, replace the K9 Body Control Module.
    • If the test lamp turns ON and OFF 
  5. Test or replace the E4A Park/Daytime Running Lamp.

Park Lamps Malfunction - Rear

  1. Ignition OFF, exterior lamps OFF, disconnect the harness connector at the appropriate component listed below. It may take up to 2 min for all vehicle systems to power down.
    • E4AL Park/Daytime Running Lamp - Left Lower (with TUJ)
    • E4AM Park/Daytime Running Lamp - Right Lower (with TUJ)
    • E4J Park Lamp - Left Front (with TR6)
    • E4N Park/Turn Signal Lamp - Left (with TUJ)
    • E4K Park Lamp - Right Front (with TR6)
    • E4P Park/Turn Signal Lamp - Right (with TUJ)
    • E2LF Side Marker Lamp - Left Front
    • E2RF Side Marker Lamp - Right Front
    • E42L Tail Lamp Assembly - Left
    • E42R Tail Lamp Assembly - Right
  2. Test for less than 10 Ω between the appropriate ground circuit terminal listed below and ground.
    • E4AL Park/Daytime Running Lamp - Left Lower terminal A (with TUJ)
    • E4AM Park/Daytime Running Lamp - Right Lower terminal A (with TUJ)
    • E4J Park Lamp - Left Front terminal G (with TR6)
    • E4N Park/Turn Signal Lamp - Left terminal G (with TUJ)
    • E4K Park Lamp - Right Front terminal G (with TR6)
    • E4P Park/Turn Signal Lamp - Right terminal G (with TUJ)
    • E2LF Side Marker Lamp - Left Front terminal 1 (without ATS-V)
    • E2RF Side Marker Lamp - Right Front terminal 1 (without ATS-V)
    • E2LF Side Marker Lamp - Left Front terminal B (with ATS-V)
    • E2RF Side Marker Lamp - Right Front terminal B (with ATS-V)
    • E42L Tail Lamp Assembly - Left terminal A
    • E42R Tail Lamp Assembly - Right terminal D (without TVN)
    • E42R Tail Lamp Assembly - Right terminal E (with TVN)
    • If 10 Ω or greater 
    1. Ignition 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.
    • If less than 10 Ω 
  3. Connect a test lamp between the appropriate control circuit terminal listed below and ground, ignition ON.
    • E4AL Park/Daytime Running Lamp - Left Lower terminal C (with TUJ)
    • E4AM Park/Daytime Running Lamp - Right Lower terminal C (with TUJ)
    • E4J Park Lamp - Left Front terminal B (with TR6)
    • E4N Park/Turn Signal Lamp - Left terminal B (with TUJ)
    • E4K Park Lamp - Right Front terminal B (with TR6)
    • E4P Park/Turn Signal Lamp - Right terminal B (with TUJ)
    • E2LF Side Marker Lamp - Left Front terminal 2 (without ATS-V)
    • E2RF Side Marker Lamp - Right Front terminal 2 (without ATS-V)
    • E2LF Side Marker Lamp - Left Front terminal A (with ATS-V)
    • E2RF Side Marker Lamp - Right Front terminal A (with ATS-V)
    • E42L Tail Lamp Assembly - Left terminal B
    • E42R Tail Lamp Assembly - Right terminal B (with T4F)
    • E42R Tail Lamp Assembly - Right terminal C (without TVN)
    • E42R Tail Lamp Assembly - Right terminal D (with TVN)
  4. Verify the test lamp turns ON and OFF when commanding the appropriate Park Lamps ON and OFF with a scan tool.
    • If the test lamp is always OFF 
    1. Ignition OFF, disconnect the X4 harness connector at the K9 Body Control Module.
    2. Test for infinite resistance between the control circuit and ground.
      • If less than infinite resistance, repair the short to ground on the circuit.
      • If infinite resistance
    3. Test for less than 2 Ω in the control circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, replace the K9 Body Control Module.
    • If the test lamp is always ON 
    1. Ignition OFF, disconnect the X4 harness connector at the K9 Body Control Module, ignition ON.
    2. Test for less than 1 V between the control circuit terminal and ground.
      • If 1 V or greater, repair the short to voltage on the circuit.
      • If less than 1 V, replace the K9 Body Control Module.
    • If the test lamp turns ON and OFF 
  5. Test or replace the park/marker/tail lamp.

License Plate Lamps Malfunction

  1. Ignition OFF, exterior lamps OFF, remove both E7 License Plate Lamps. It may take up to 2 min for all vehicle systems to power down.
  2. Test for less than 5 Ω between the ground circuit terminal 2 and ground.
    • If 5 Ω or greater 
    1. Ignition 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.
    • If less than 5 Ω 
  3. Connect a test lamp between the E7L License Plate Lamp - Left control circuit terminal 1 and ground, ignition ON.
  4. Verify the test lamp turns ON and OFF when commanding the License Plate Lamps ON and OFF with a scan tool.
    • If the test lamp is always OFF 
    1. Ignition OFF, disconnect the X4 harness connector at the K9 Body Control Module.
    2. Test for infinite resistance between the control circuit and ground.
      • If less than infinite resistance, repair the short to ground on the circuit.
      • If infinite resistance
    3. Test for less than 2 Ω in the control circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, replace the K9 Body Control Module.
    • If the test lamp is always ON 
    1. Ignition OFF, disconnect the X4 harness connector at the K9 Body Control Module, ignition ON.
    2. Test for less than 1 V between the control circuit terminal and ground.
      • If 1 V or greater, repair the short to voltage on the circuit.
      • If less than 1 V, replace the K9 Body Control Module.
    • If the test lamp turns ON and OFF 
  5. Connect a test lamp between the E7R License Plate Lamp - Right control circuit terminal 1 and ground, ignition ON.
  6. Verify the test lamp turns ON and OFF when commanding the License Plate Lamps ON and OFF with a scan tool.
    • If the test lamp is always OFF 
    1. Ignition OFF, disconnect the X4 harness connector at the K9 Body Control Module.
    2. Test for infinite resistance between the control circuit and ground.
      • If less than infinite resistance, repair the short to ground on the circuit.
      • If infinite resistance
    3. Test for less than 2 Ω in the control circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, replace the K9 Body Control Module.
    • If the test lamp turns ON and OFF 
  7. Test or replace the E7 License Plate Lamp.
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