Buick Regal: DTC B3415 or B3425

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.

DTC Descriptors

DTC B3415 01

Headlamp Leveling Control Module Front Axle Sensor Supply Circuit Short to Battery

DTC B3425 01

Headlamp Leveling Control Module Rear Axle Sensor Supply Circuit Short to Battery

Diagnostic Fault Information

1. Headlamp Leveling Malfunction

Circuit/System Description

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 control module 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 control modules and the left and right headlamp leveling control modules communicate with the left and right headlamp leveling actuators via the LIN serial data circuit.

Conditions for Running the DTC

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

Conditions for Setting the DTC

DTC B3415 01

The DTC will set when the headlamp control module detects no signal and low voltage on the front sensor signal circuit.

DTC B3425 01

The DTC will set when the headlamp control module detects no signal and low voltage on the rear sensor signal circuit.

Actions Taken When the DTC Sets

• The headlamp control module disables the headlamp leveling system.
• The driver information center will display Service Headlight Leveling.

Conditions for Clearing the DTC

• The condition responsible for setting the DTC no longer exists.
• A history DTC will clear once 100 consecutive malfunction-free ignition cycles have occurred.

Diagnostic Aids

No parts are serviceable within the headlamp assemblies so complete headlamp assembly replacement is necessary. The appropriate K135 Headlamp Low Beam Control Module, K191 Headlamp High Beam Control Module, and K166 Multifunction LED Control Module may be reused when replacing the headlamp assembly.

Reference Information

Schematic Reference

Headlights/Daytime Running Lights (DRL) Wiring Schematics

Connector End View Reference

COMPONENT CONNECTOR END VIEWS - INDEX

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 Testing

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.

• 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 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.
   • 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 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.

• Go to next step: If between 4.8 - 5.2 V

5. Test for 4.8 - 5.2 V between the 5 V reference circuit terminal 1 and the signal circuit terminal 3.

• If less than 4.8 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 signal circuit terminal 3 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. 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.

• Go to next step: If between 4.8 - 5.2 V

6. Install a 3 A fused jumper wire between the 5 V reference circuit terminal 1 and the signal circuit terminal 3, engine RUNNING.

7. Verify the appropriate scan tool Suspension Manually Entered Trim Height parameter is greater than 0 mm.

• If not greater than 0 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, replace the K26 Headlamp Control Module.

• Go to next step: If greater than 0 mm

8. Test or replace the appropriate B51 Suspension Height Sensor.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the repair.

• Suspension Position Sensor Calibration
• Control Module References for headlamp control module replacement, programming, and setup

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