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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 >> Headlamp Leveling Malfunction (Automatic) >> 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.

Headlamp Leveling Actuator Malfunction

  1. Ignition OFF, exterior lamps OFF, disconnect the harness connector at the appropriate E13 Headlamp Assembly.
  2. Test for less than 15 Ω between the ground circuit terminal 7 and ground.
    • 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. Ignition ON.
  4. Verify a test lamp illuminates between the B+ circuit terminal 8 and ground.
    • If the test lamp does not illuminate 
    1. Ignition OFF, disconnect the X1 harness connector at the X50A Fuse Block - Underhood.
    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
    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 X50A Fuse Block - Underhood.
    • If the test lamp illuminates 
  5. Test or replace the K26 Headlamp Control Module.
  6. Ignition ON.
  7. Verify the appropriate headlamp operates to the UP and DOWN positions when commanding the appropriate Headlamp Vertical Motor UP and DOWN with a scan tool.
    • If the headlamp does not operate UP and DOWN 
    • Test or replace the M29 Headlamp Leveling Actuator.
    • If the headlamp operates UP and DOWN 
  8. All OK.

Headlamp Leveling Sensor Malfunction

  1. Ignition OFF, disconnect the harness connector at the appropriate B152L Suspension Position Sensor, ignition ON.
  2. Verify a test lamp illuminates between the low reference circuit terminal 2 and B+.
    • If the test lamp does not illuminate 
    1. Ignition OFF, disconnect the harness connector at the K26 Headlamp Control Module.
    2. Test for less than 2 Ω in the low reference circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, replace the K26 Headlamp Control Module.
    • If the test lamp illuminates 
  3. Ignition ON.
  4. Test for 4.8-5.2 V between the 5 V reference circuit terminal 1 and ground.
    • If less than 4.8 V 
    1. Ignition OFF, disconnect the harness connector at the K26 Headlamp Control Module.
    2. Test for infinite resistance between the 5 V reference 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 5 V reference circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, replace the K26 Headlamp Control Module.
    • If greater than 5.2 V 
    1. Ignition OFF, disconnect the harness connector at the K26 Headlamp Control Module, ignition ON.
    2. Test for less than 1 V between the 5 V reference circuit and ground.
      • If 1 V or greater, repair the short to voltage on the circuit.
      • If less than 1 V, replace the K26 Headlamp Control Module.
    • If between 4.8-5.2 V 
  5. Verify the appropriate scan tool Suspension Position Sensor parameter is less than 1 V.
    • If 1 V or greater 
    1. Ignition OFF, disconnect the harness connector at the K26 Headlamp Control Module, ignition ON.
    2. Test for less than 1 V between the signal circuit terminal 3 and ground.
      • If 1 V or greater, repair the short to voltage on the circuit.
      • If less than 1 V, replace the K26 Headlamp Control Module.
    • If less than 1 V 
  6. Install a 3 A fused jumper wire between the 5 V reference circuit terminal 1 and the signal circuit terminal 3.
  7. Engine RUNNING, verify the appropriate scan tool Suspension Position Sensor parameter is greater than 4.8 V.
    • If less than 4.8 V 
    1. Ignition OFF, disconnect the harness connector at the K26 Headlamp Control Module.
    2. Test for infinite resistance between the signal 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 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 K26 Headlamp Control Module.
    • If 4.8 V or greater 
  8. Test or replace the appropriate B152L Suspension Position Sensor.
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