B2648

CIRCUIT DESCRIPTION
The ambient light sensor indicates the light level to control the automatic headlamps and park lamps. The Body Control Module (BCM) provides a 5 volt reference signal to the ambient light sensor through the ambient light sensor signal circuit. The BCM receives the modified voltage from the ambient light sensor through the ambient light sensor low reference circuit. A low voltage under 1.5 V, signals a dark condition to the BCM and vice versa.

CONDITIONS FOR RUNNING THE DTC
The ignition switch is in the on position.

CONDITIONS FOR SETTING THE DTC
Any of the following conditions will set this DTC:
^ The ambient light sensor signal reference circuit is shorted to battery for 5 seconds.
^ The ambient light sensor signal reference circuit is shorted to battery for 5 seconds.

ACTION TAKEN WHEN THE DTC SETS
^ The ALC headlamp and park lamp relay control are disabled for the remainder of the ignition cycle.
^ The SERVICE indicator illuminates.
^ The check gauges 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
If the DTC is a history DTC, the problem may be intermittent. Refer to Diagnostic Aids for Circuit Testing and Wiring Repair procedures.

TEST DESCRIPTION

Steps 1-4:

Steps 5-6:

The number below refers to the step number on the diagnostic table.
2. The normal operating voltage of the photocell is 0.5-4.5 volts.