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Home >> GMC >> 2018 >> Acadia Denali, FWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 334 (Lighting System) >> 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 GMC Acadia. 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 3 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 5 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 5 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 5 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

  1. Ignition OFF, disconnect the X5 harness connector at the K9 Body Control Module, ignition ON.
  2. Verify a test lamp illuminates between the B+ circuit terminal 4 and ground.
    • If the test lamp does not illuminate and the circuit fuse is good 
    1. Ignition OFF, remove the F1DA fuse at the X51A Fuse Block - Instrument Panel.
    2. Test for less than 2 Ω in the B+ circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, 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. Ignition OFF, remove the F1DA fuse at the X51A Fuse Block - Instrument Panel.
    2. Test for infinite resistance between the B+ circuit 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 the test lamp illuminates 
  3. Ignition OFF, connect the X5 harness connector at the K9 Body Control Module.
  4. 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.
    • E4N Park/Turn Signal Lamp - Left (with T3W)
    • E4P Park/Turn Signal Lamp - Right (with T3W)
    • E5S Tail/Stop and Turn Signal Lamp - Left
    • E5T Tail/Stop and Turn Signal Lamp - Right
    • E13LA Headlamp Assembly - Left (with T3W/T7E)
    • E13RA Headlamp Assembly - Right (with T3W/T7E)
    • E43L Liftgate Tail Lamp Assembly - Left
    • E43R Liftgate Tail Lamp Assembly - Right
  5. Test for less than 5 Ω between the appropriate ground circuit terminal listed below and ground.
    • E4N Park/Turn Signal Lamp - Left terminal 3 (with T3W)
    • E4P Park/Turn Signal Lamp - Right terminal 3 (with T3W)
    • E5S Tail/Stop and Turn Signal Lamp - Left socket terminal
    • E5T Tail/Stop and Turn Signal Lamp - Right socket terminal
    • E13LA Headlamp Assembly - Left terminal 4 (with T3W)
    • E13LA Headlamp Assembly - Left terminal 6 (with T7E)
    • E13RA Headlamp Assembly - Right terminal 4 (with T3W)
    • E13RA Headlamp Assembly - Right terminal 6 (with T7E)
    • E43L Liftgate Tail Lamp Assembly - Left terminal 1
    • E43R Liftgate Tail Lamp Assembly - Right terminal 1
    • 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 
  6. Connect a test lamp between the appropriate control circuit terminal listed below and ground, ignition ON.
    • E4N Park/Turn Signal Lamp - Left terminal 2 (with T3W)
    • E4P Park/Turn Signal Lamp - Right terminal 2 (with T3W)
    • E5S Tail/Stop and Turn Signal Lamp - Left socket terminal
    • E5T Tail/Stop and Turn Signal Lamp - Right socket terminal
    • E13LA Headlamp Assembly - Left terminal 1 (with T3W)
    • E13LA Headlamp Assembly - Left terminal 1 (with T7E)
    • E13RA Headlamp Assembly - Right terminal 1 (with T3W)
    • E13RA Headlamp Assembly - Right terminal 1 (with T7E)
    • E43L Liftgate Tail Lamp Assembly - Left terminal 3
    • E43R Liftgate Tail Lamp Assembly - Right terminal 3
  7. 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 appropriate harness connector listed below at the K9 Body Control Module.
      • X4 - rear park lamps
      • X5 - left front park lamps
      • X7 - right front park lamps
    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 - rear park lamps
      • X5 - left front park lamps
      • X7 - right front park lamps
    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 
  8. Test or replace the park/side marker/tail lamp.

License Plate Lamps Malfunction

  1. Ignition OFF, exterior lamps OFF, remove both E7 License Plate Lamp bulbs. It may take up to 2 min for all vehicle systems to power down.
  2. Test for less than 5 Ω between each 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. Ignition OFF.
  6. Connect a test lamp between the E7R License Plate Lamp - Right control circuit terminal 1 and ground, ignition ON.
  7. 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 the test lamp turns ON and OFF 
  8. Test or replace the E7 License Plate Lamp bulb.
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