• Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
• Review Strategy Based Diagnosis for an overview of the diagnostic approach.
• Diagnostic Procedure Instructions provides an overview of each diagnostic category.

Each headlamp assembly contains a headlamp leveling actuator that is controlled by the headlamp control module. The front and rear suspension position sensors provide the headlamp leveling control with suspension position information. Each sensor receives a 5 V reference, signal, and low reference circuits from the headlamp control module. The sensors are connected to the control arms of the front and rear suspension. As the vehicle travels, the suspension compresses and rebounds moving the suspension position sensor arms. This causes the signal output of the sensor to change. The headlamp control module compares the information from both suspension position sensors and adjusts the headlamp leveling as needed. The headlamp control module communicates with the left and right headlamp leveling actuators via the LIN serial data circuit.

• Battery voltage must be between 9-16 V.
• Engine RUNNING.
• Headlamps ON.

• The headlamp control module detects a short to ground or an open/high resistance in the left headlamp leveling actuator LIN bus circuit.
• The headlamp control module detects an open/high resistance in the left headlamp leveling actuator ground circuit.

• The headlamp control module detects a short to ground or an open/high resistance in the right headlamp leveling actuator LIN bus circuit.
• The headlamp control module detects an open/high resistance in the right headlamp leveling actuator ground circuit.

• The headlamp control module disables the headlamp leveling system.
• Service head light leveling indication ON.
• Advanced front lighting system fault indication ON.

• The condition responsible for setting the DTC no longer exists and the ignition is cycled.
• A history DTC will clear once 50 consecutive malfunction-free ignition cycles have occurred.

• Headlights/Daytime Running Lights (DRL) Schematics
• Ground Distribution Schematics

Master Electrical Component List

Exterior Lighting Systems Description and Operation

• Circuit Testing
• Connector Repairs
• Testing for Intermittent Conditions and Poor Connections
• Wiring Repairs

Control Module References for scan tool information

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 8 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 6 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. Replace the M29 Headlamp Leveling Actuator.
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

  Replace the K26 Headlamp Control Module.

• If the headlamp operates UP and DOWN
8. All OK.

Perform the Diagnostic Repair Verificationafter completing the repair.

• Control Module References for headlamp control module replacement, programming, and setup