B2647

CIRCUIT DESCRIPTION
The body control module (BCM) uses the ambient light sensor signal in order to control the daytime running lamps system. The ambient light sensor is connected directly to the BCM through the signal circuit and the reference circuit of the ambient light sensor.

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

CONDITIONS FOR SETTING THE DTC
^ The BCM detects a short to ground or a short to battery positive voltage in the signal circuit of the DRL ambient light sensor.
^ The BCM detects a short to ground in the low reference 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 B2647 in memory.
^ The SERVICE VEHICLE SOON telltale illuminates.
^ The headlamps, the park lamps, the tail lamps and the marker lamps illuminate to night intensity.

CONDITIONS FOR CLEARING THE DTC
^ The BCM no longer detects a fault in the signal circuit of the DRL ambient light sensor for more than 1.0 second.
^ The BCM no longer detects a fault in the low reference circuit of the DRL ambient light sensor for more than 1.0 second.
^ A history DTC 82647 clears after 100 consecutive ignition cycles.
^ The BCM receives the Clear Code command from the scan tool.

DIAGNOSTIC AIDS
^ If the DTC B2647 is a history DTC, the fault may be intermittent. Refer to Testing for Intermittent and Poor Connections in Diagnostic Aids.
^ The following conditions may cause an intermittent malfunction to occur:
- An intermittent short to ground or a short to battery positive voltage in the signal circuit of the DRL ambient light sensor.
- An intermittent short to ground in the low reference circuit of the DRL ambient light sensor.
- An intermittent internal short to ground in the ambient light sensor.
- An intermittent internal short to ground in the BCM.

TEST DESCRIPTION

Steps 4-12:

Steps 4-12:

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.