• 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 motor that is controlled by the headlamp control module. The front and rear suspension height sensors provide the headlamp control module with suspension height 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 height sensor arms. This causes the signal output of the sensor to change. The headlamp control module compares the information from both suspension height sensors and adjusts the headlamp leveling as needed.

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

The headlamp control module detects a short to ground or an open/high resistance in the front suspension height sensor signal circuit.

The headlamp control module detects a short to voltage or an open/high resistance in the front suspension height sensor signal circuit.

The headlamp control module receives a signal from the front suspension height sensor signal circuit that is not within the normal operating range.

The headlamp control module detects a short to ground or an open/high resistance in the rear suspension height sensor signal circuit.

The headlamp control module detects a short to voltage or an open/high resistance in the rear suspension height sensor signal circuit.

The headlamp control module receives a signal from the rear suspension height sensor signal circuit that is not within the normal operating range.

• The headlamp control module disables the headlamp leveling system.
• The driver information center will display “Adaptive Forward Lighting” and “Headlamp Leveling Malfunction”.
• On vehicles equipped with both AFL and headlamp leveling, the AFL system will remain active.

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

Headlights/Daytime Running Lights (DRL) 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

J-38522 Variable Signal Generator

For equivalent regional tools, refer to Special Tools

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 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 Leveling Position Sensor Signal parameter is less than 1 mm.
• If 1 mm 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 mm
6. Ignition OFF.
7. Connect the red lead of the J-38522 Variable Signal Generator to the signal circuit terminal 3 and the black lead of the J-38522 Variable Signal Generator to the low reference circuit terminal 2.
8. Adjust the J-38522 Variable Signal Generator to the settings listed below:
• Signal control to 5 V
• Frequency control to 250 Hz
• Duty cycle control to the 60%
9. Ignition ON, verify the appropriate scan tool Leveling Position Sensor parameter is 11 mm.
• If not 11 mm
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 11 mm
10. Test or replace the B51 Suspension Height Sensor.

Perform the Diagnostic Repair Verification after completing the repair.

• Control Module References for Headlamp Control Module replacement, programming, and setup