B2648

CIRCUIT DESCRIPTION
The Body Control Module (BCM) uses the ambient light sensor signal to control the daytime running lamps system. The ambient light sensor is connected directly to the BCM.

CONDITIONS FOR RUNNING THE DTC
^ Voltage supplied to the module is in the normal operating voltage range (approximately 10 - 16 volts).
^ The DRL feature must be enabled.

CONDITIONS FOR SETTING THE DTC
^ The BCM detects a short to voltage in the signal circuit of the DRL ambient light sensor.
^ The condition must be present for more than 1.0 second.

ACTION TAKEN WHEN THE DTC SETS
^ The BCM stores DTC B2648 in memory
^ The SERVICE VEHICLE SOON telltale illuminates
^ The headlamps, the park lamps, the tail lamps and the marker lamps illuminate to low light intensity

CONDITIONS FOR CLEARING THE DTC
^ A current DTC B2648 clears when the BCM no longer detects the fault in the signal circuit of the DRL ambient light sensor.
^ A history DTC B2648 clears after 100 consecutive ignition cycles.
^ The BCM receives the Clear Code command from the scan tool.

DIAGNOSTIC AIDS
^ If the DTC B2648 is a history DTC, the fault may be intermittent. Refer to Testing for Intermittent and Poor Connections in Diagrams.
^ An intermittent short to voltage in the following locations may cause an intermittent malfunction to occur:
- The signal circuit of the DRL ambient light sensor
- The ambient light sensor
- The BCM

TEST DESCRIPTION

Steps 1-12:

The number(s) below refer to the step number(s) on the diagnostic table.
3. This step tests for the proper operation of the circuit in the high voltage range.
4. This step tests for the proper operation of the circuit in the low voltage range. If the fuse in the jumper opens when you perform this test, the signal circuit is shorted to voltage.