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Home >> Cadillac >> 2018 >> XT5 Platinum >> Repair and Diagnosis >> Accessories & Equipment >> Headlights >> Lighting System - Diagnostic Information And Procedures (DTC B3950 - C0297) >> Diagnostic Information and Procedures >> Headlamp Leveling Malfunction >> Circuit/System Testing

Circuit/System Testing

Headlamp Leveling Actuator Malfunction

  1. Ignition OFF, disconnect the KR50 Headlamp Relay.
  2. Verify a test lamp illuminates between the B+ circuit terminal 85 and ground.
    • If the test lamp does not illuminate 

      Replace the X50A Fuse Block - Underhood.

    • Go to next step: If the test lamp illuminates 
  3. Verify a test lamp illuminates between the B+ circuit terminal 30 and ground.
    • If the test lamp does not illuminate 

      Replace the X50A Fuse Block - Underhood.

    • Go to next step: If the test lamp illuminates 
  4. Connect a test lamp between the control circuit terminal 86 and B+, ignition ON.
  5. Verify the test lamp turns ON and OFF when commanding the headlamps ON and OFF with the S78 Turn Signal/Multifunction Switch.
    • If the test lamp is always OFF 
    1. Ignition OFF, disconnect the X5 harness connector at the K9 Body Control Module, ignition ON.
    2. Test for less than 1 V between the control circuit terminal 13 and ground.
      • If 1 V or greater, repair the short to voltage on the circuit.
      • Go to next step: If less than 1 V
    3. Ignition OFF.
    4. 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 X5 harness connector at the K9 Body Control Module.
    2. Test for infinite resistance between the control circuit terminal 13 and ground.
      • If less than infinite resistance, repair the short to ground on the circuit.
      • If infinite resistance, replace the K9 Body Control Module.
    • Go to next step: If the test lamp turns ON and OFF 
  6. Ignition OFF, connect the KR50 Headlamp Relay.
  7. Ignition OFF, exterior lamps OFF, disconnect the harness connector at the appropriate E13 Headlamp Assembly. It may take up to 2 min for all vehicle systems to power down.
  8. Test for less than 5 Ω between the ground circuit terminal 9 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.
    • Go to next step: If less than 5 Ω 
  9. Connect a test lamp between the control circuit terminal 5 and ground, ignition ON.
  10. Verify the test lamp turns ON and OFF when commanding the headlamps ON and OFF with the S78 Turn Signal/Multifunction Switch.
    • If the test lamp is always OFF 
    1. Ignition OFF, disconnect the X4 harness connector at the X50A Fuse Block - Underhood.
    2. Test for infinite resistance between the control circuit terminal 5 and ground.
      • If less than infinite resistance, repair the short to ground on the circuit.
      • Go to next step: 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 KR50 Headlamp Relay.
    • If the test lamp is always ON 
    1. Ignition OFF, disconnect the X4 harness connector at the X50A Fuse Block - Underhood, ignition ON.
    2. Test for less than 1 V between the control circuit terminal 5 and ground.
      • If 1 V or greater, repair the short to voltage on the circuit.
      • If less than 1 V, replace the KR50 Headlamp Relay.
    • Go to next step: If the test lamp turns ON and OFF 
  11. Ignition OFF.
  12. Test or replace the K28 Headlamp Leveling Control Module.
  13. Ignition ON.
  14. 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 E13 Headlamp Assembly.

    • Go to next step: If the headlamp operates UP and DOWN 
  15. All OK.

Headlamp Leveling Sensor Malfunction

  1. Ignition OFF, disconnect the harness connector at the appropriate B51 Suspension Height 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 K28 Headlamp Leveling 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 K28 Headlamp Leveling Control Module.
    • Go to next step: 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 K28 Headlamp Leveling 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.
      • Go to next step: 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 K28 Headlamp Leveling Control Module.
    • If greater than 5.2 V 
    1. Ignition OFF, disconnect the harness connector at the K28 Headlamp Leveling 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 K28 Headlamp Leveling Control Module.
    • Go to next step: If between 4.8 - 5.2 V 
  5. Verify the appropriate scan tool Leveling Position Sensor Signal parameter is less than 5%.
    • If 5% or greater 
    1. Ignition OFF, disconnect the harness connector at the K28 Headlamp Leveling 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 K28 Headlamp Leveling Control Module.
    • Go to next step: If less than 5% 
  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 Leveling Position Sensor Signal parameter is greater than 90%.
    • If less than 90% 
    1. Ignition OFF, disconnect the harness connector at the K28 Headlamp Leveling 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.
      • Go to next step: 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 K28 Headlamp Leveling Control Module.
    • Go to next step: If 90% or greater 
  8. Test or replace the B51 Suspension Height Sensor.
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