B2575

DTC B2575

CIRCUIT DESCRIPTION
The body control module (BCM) turns on the automatic lighting control (ALC) headlamp relay when the ambient light sensor senses a dark condition. Battery positive voltage is supplied to the relay at all times through the LH HDLP fuse. The BCM grounds the ALC headlamp relay control circuit in order to activate the relay.

CONDITIONS FOR RUNNING THE DTC
- The ignition switch is in the ON position.
- The ambient light sensor senses a dark condition (ALC headlamps on).

CONDITIONS FOR SETTING THE DTC
The ALC headlamp relay control circuit is open for 5 seconds.

ACTION TAKEN WHEN THE DTC SETS
- The SERVICE indicator illuminates.
- The check gages chime sounds.

CONDITIONS FOR CLEARING THE DTC
- The conditions for setting the DTC are no longer present.
- A history DTC clears after 100 malfunction free ignition cycles.
- The BCM receives the clear code command from the scan tool.

DIAGNOSTIC AIDS
- Turn the ignition switch to the OFF position, cover the light sensor on the dash, wait for 15 seconds and then return the ignition to the ON position. The low beams should illuminate.
- If the DTC is a history DTC, the problem may be intermittent.

TEST DESCRIPTION

Steps 1-12:

The numbers below refer to the step numbers on the diagnostic table.
2. Listen for an audible click when the ALC headlamp relay operates. Command both the ON and OFF states. Repeat the commands as necessary.
3. Tests for voltage at the coil side of the ALC headlamp relay. The LH HDLP fuse supplies power to the coil side of the ALC headlamp relay.
4. Verifies that the body control module is providing ground to the ALC headlamp relay.