Battery positive voltage is applied to the headlamp control module at all times. The headlamp control module has a normal operational voltage range of about 12.5-16 V and is only fully functional with the ignition switch is in the RUN position and the headlamp switch in the AUTO position. The communications enable signal from the body control module (BCM) wakes the headlamp control module microprocessor. The headlamp control module receives serial data messages from the engine control module (ECM), transmission control module (TCM), electronic brake control module (EBCM), and BCM with information regarding power mode, speed, steering angle, transmission gear selection, and headlamp switch status. The headlamp control module calculates the headlamp angle and sends commands to the left and right adaptive forward lighting system headlamp actuators. The headlamp actuators drive the headlamps to the position commanded by the headlamp control module. The headlamp control module monitors the headlamp actuator motor control circuits for proper circuit continuity and for shorts to ground or voltage. If a malfunction is detected, a DTC will be stored in memory and the driver will be notified with a message displayed over the driver information center located on the instrument cluster.

B0984 00 or B0985 00

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

The condition responsible for setting the DTC no longer exists.

Schematic Reference

Headlight Leveling Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Exterior Lighting Systems Description and Operation

Electrical Information Reference

Scan Tool Reference

Control Module References for scan tool information

1. Verify that DTC B3415 is not present.

⇒	If DTC is present, refer to DTC B3415

1. Ignition OFF, disconnect the harness connector at the appropriate headlamp assembly.
2. Test for less than 5 Ω between the ground circuit terminal 8 and ground.

⇒	If greater than the specified range, test the ground circuit for an open/high resistance.

3. Ignition ON, connect a test lamp between the ignition circuit terminal 6 and ground. The test lamp should illuminate.

⇒	If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance.

4. If all circuits test normal, replace the appropriate headlamp assembly. Verify that the DTC do not reset.

⇒	If the DTC resets, replace the K26 Headlamp Control Module.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.