For 1990-2009 cars

### Diagnostic Instructions

• | 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.

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
Headlamp Leveling Sensor 5 Volt Reference - Front | B3415 02 | 1 | B3415 01 | --
Headlamp Leveling Sensor 5 Volt Reference - Rear | 1 | 1 | 1 | --
Headlamp Leveling Sensor Signal - Front | B3410 02 | B3410 05 | B3410 05 | B3410 08
Headlamp Leveling Sensor Signal - Rear | B3420 02 | B3420 05 | B3420 05 | B3420 08
Headlamp Leveling Motor Control Circuit 1 - Left | B3435 02 | B3435 05 | B3435 05 | B3435 54
Headlamp Leveling Motor Control Circuit 2 - Left | B3435 02 | B3435 05 | B3435 05 | B3435 54
Headlamp Leveling Motor Control Circuit 3 - Left | B3435 02 | B3435 05 | B3435 05 | B3435 54
Headlamp Leveling Motor Control Circuit 4 - Left | B3435 02 | B3435 05 | B3435 05 | B3435 54
Headlamp Leveling Motor Control Circuit 1 - Right | B3440 02 | B3440 05 | B3440 05 | B3435 54
Headlamp Leveling Motor Control Circuit 2 - Right | B3440 02 | B3440 05 | B3440 05 | B3435 54
Headlamp Leveling Motor Control Circuit 3 - Right | B3440 02 | B3440 05 | B3440 05 | B3435 54
Headlamp Leveling Motor Control Circuit 4 - Right | B3440 02 | B3440 05 | B3440 05 | B3440 39, B3440 54
Headlamp Leveling Sensor Low Reference - Front | -- | 1 | 1 | --
Headlamp Leveling Sensor Low Reference - Rear | -- | 1 | 1 | --
1. Headlamp Leveling Malfunction

### Circuit/System Description

Each headlamp assembly contains a headlamp leveling motor that is controlled by the headlamp control module. The front and rear headlamp leveling 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

Headlights Schematics

#### Connector End View Reference

Component Connector End Views

#### Description and Operation

Exterior Lighting Systems Description and Operation

#### Electrical Information Reference

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

#### Scan Tool Reference

Control Module References for scan tool information

### Circuit/System Verification

1. Ignition ON, with a scan tool, command the AHL 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 parameter should be between 58 and 62 degrees.

⇒ | If the parameter is not within the specified range, refer to Headlamp Leveling Sensor Malfunction.

3. Observe the scan tool Rear Leveling Position Sensor voltage parameter. The parameter should be between 57 and 61 degrees.

⇒ | If the parameter 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 inoperative headlamp.
2. Remove the COMM ENABLE 10A fuse.
3. Ignition OFF, scan tool OFF, test for 20K -22K ohms between each control circuit terminal listed below and ground.

• | Headlamp leveling motor control terminal 3

• | Headlamp leveling motor control terminal 4

• | Headlamp leveling motor control terminal 5

• | Headlamp leveling motor control terminal 10

⇒ | 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.

⇒ | If less than the specified range, test the control circuit for a short to ground. If the circuit tests normal, replace the headlamp control module.

4. Install the COMM ENABLE 10A fuse.
5. Ignition ON, scan tool OFF, headlamps ON, verify that a test lamp does not illuminate between each control circuit terminal listed below and ground.

• | Headlamp leveling motor control terminal 3

• | Headlamp leveling motor control terminal 4

• | Headlamp leveling motor control terminal 5

• | Headlamp leveling motor control terminal 10

⇒ | If the test lamp illuminates, test the control circuit for a short to voltage. If the circuit tests normal, replace the headlamp control module.

6. 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 ohms between the low reference circuit terminal 1 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 2 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 appropriate scan tool Leveling Position Sensor parameter is less than 59 degrees.

⇒ | If greater than the specified range, test the signal circuit terminal 3 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 3 and the 5-volt reference circuit terminal 2. Verify the appropriate scan tool Leveling Position Sensor parameter is greater than 59 degrees.

⇒ | 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, replace the appropriate headlamp leveling sensor.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Headlamp Replacement

• | Headlamp Leveling Control Module Replacement

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