Operation CHARM: Car repair manuals for everyone.
Home >> Cadillac >> 2008 >> CTS RWD V6-3.6L >> Repair and Diagnosis >> Lighting and Horns >> Testing and Inspection >> Symptom Related Diagnostic Procedures >> Headlamp Leveling Malfunction

Headlamp Leveling Malfunction



Headlamp Leveling Malfunction

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle (Initial Inspection and Diagnostic Overview) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Initial Inspection and Diagnostic Overview) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Initial Inspection and Diagnostic Overview) provides an overview of each diagnostic category.



Diagnostic Fault Information






Circuit/System Description

Each headlamp assembly contains a headlamp leveling motor that is controlled by the headlamp control module. The front and rear suspension position sensors provide the headlamp control module with suspension position information. Each sensor receives a 5-volt 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 is wired to each headlamp leveling motor with 4 directional motor control circuits.


Reference Information
Schematic Reference

Headlight Leveling Schematics (Headlight Leveling Schematics)
Connector End View Reference

Component Connector End Views (Connector Views)
Description and Operation

Exterior Lighting Systems Description and Operation (Exterior Lighting Systems Description and Operation)
Electrical Information Reference

* Circuit Testing (Component Tests and General Diagnostics)
* Connector Repairs (Component Tests and General Diagnostics)
* Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics)
* Wiring Repairs (Component Tests and General Diagnostics)

Scan Tool Reference

Control Module References (Programming and Relearning) for scan tool information


Circuit/System Verification

1. Ignition ON, with a scan tool, command the DHL motor control UP and DOWN while observing both headlamps. Both headlamps should operate to the UP and DOWN positions when commanded.

• If the headlamps do not operate to the UP and DOWN positions when commanded, refer to Headlamp Leveling Actuator Malfunction.

2. Observe the scan tool front leveling position sensor voltage parameter. The reading should be between 0.5 and 4.9 volts.

• If the reading is not within the specified range, refer to Headlamp Leveling Sensor Malfunction.

3. Observe the scan tool rear leveling position sensor voltage parameter. The reading should be between 0.5 and 4.9 volts.

• If the reading is not within the specified range, refer to Headlamp Leveling Sensor Malfunction.




Circuit/System Testing


Headlamp Leveling Actuator Malfunction
1. Ignition OFF, disconnect the harness connector at the appropriate headlamp leveling motor.
2. Ignition OFF, test for less than 10.0 ohms between the motor control circuit terminal 1 and ground.

• If greater than the specified range, test the control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the headlamp control module.

3. Ignition OFF, test for less than 10.0 ohms between the motor control circuit terminal 2 and ground.

• If greater than the specified range, test the control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the headlamp control module.

4. Ignition OFF, test for less than 10.0 ohms between the motor control circuit terminal 3 and ground.

• If greater than the specified range, test the control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the headlamp control module.

5. Ignition OFF, test for less than 10.0 ohms between the motor control circuit terminal 4 and ground.

• If greater than the specified range, test the control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the headlamp control module.

6. Connect a test lamp between control circuit terminal 1 and control circuit terminal 3.
7. Command the DHL motor control to the UP and DOWN positions with a scan tool. The test lamp should turn ON when commanding the UP and DOWN states.

• If the test lamp remains OFF during either of the commands, test for a short to ground on either control circuit. If the circuits test normal, replace the headlamp control module.

8. Connect a test lamp between control circuit terminal 2 and control circuit terminal 4.
9. Command the DHL motor control to the UP and DOWN positions with a scan tool. The test lamp should turn ON when commanding the UP and DOWN states.

• If the test lamp remains OFF during either of the commands, test for a short to ground on either control circuit. If the circuits test normal, replace the headlamp control module.

10. If all circuits test normal, replace the appropriate headlamp assembly.



Headlamp Leveling Sensor Malfunction
1. Ignition OFF, disconnect the harness connector at the appropriate headlamp leveling sensor.
2. Ignition OFF, test for less than 10.0 ohms between the low reference circuit terminal C and ground.

• If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the headlamp control module.

3. Ignition ON, test for 4.8-5.2 volts between the 5-volt reference circuit terminal A and ground.

• If less than the specified range, test the 5-volt reference circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the headlamp control module.
• If greater than the specified range, test the 5-volt reference circuit for a short to voltage. If the circuit tests normal, replace the headlamp control module.

4. Verify the scan tool leveling position sensor parameter is less than 0.5-volts.

• If greater than the specified range, test the signal circuit terminal B for a short to voltage. If the circuit tests normal, replace the headlamp control module.

5. Install a 3A fused jumper wire between the signal circuit terminal B and the 5-volt reference circuit terminal A. Verify the scan tool leveling position sensor parameter is greater than 4.8-volts.

• If less than the specified range, test the signal circuit for short to ground or an open/high resistance. If the circuit tests normal, replace the headlamp control module.

6. If all circuits test normal, test or replace the appropriate headlamp leveling sensor.



Repair Instructions

Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.

* Headlamp Assembly or Headlamp Bulb and/or Cornering, Sidemarker, Park, Turn Signal Bulb Replacement (Minus TT6/TT7/TT8/T84/T85) (Service and Repair)Headlamp Assembly or Headlamp Bulb and/or Cornering, Sidemarker, Park, Turn Signal Bulb Replacement (T84/T85) (Service and Repair)Headlamp Assembly or Headlamp Bulb and/or Cornering, Sidemarker, Park, Turn Signal Bulb Replacement (TT6) (Service and Repair)Headlamp Assembly or Headlamp Bulb and/or Cornering, Sidemarker, Park, Turn Signal Bulb Replacement (TT8) (Service and Repair)Headlamp Assembly or Headlamp Bulb and/or Cornering, Sidemarker, Park, Turn Signal Bulb Replacement (TT7) (Service and Repair)
* Headlamp Leveling Front Suspension Height Sensor Replacement (Headlamp Leveling Front Suspension Height Sensor Replacement)
* Headlamp Leveling Rear Suspension Height Sensor Replacement (Headlamp Leveling Rear Suspension Height Sensor Replacement)
* Control Module References (Programming and Relearning) for headlamp control module replacement, setup, and programming


pro multis · About Operation CHARM