B2647

Diagnostic Chart (Part 1 Of 2):

Diagnostic Chart (Part 2 Of 2):

Schematic:

CIRCUIT DESCRIPTION
The Body Control Module (BCM) uses the ambient light sensor signal to control the automatic headlamp control system. The ambient light sensor is connected directly to the BCM through the control ambient light signal circuit and the headlamp auto control ambient light ground reference circuit.

CONDITIONS FOR RUNNING THE DTC
The DRL feature or the automatic headlamp control feature must be enabled.

CONDITIONS FOR SETTING THE DTC
^ The BCM detects a short to ground in the headlamp auto control ambient light ground reference circuit.
^ The condition above must be present for more than 0.3 seconds.

ACTION TAKEN WHEN DTC SETS
^ The BCM stores DTC B2647 in memory.
^ The SERVICE VEHICLE SOON telltale will illuminate
^ The headlamps, park lamps, tail lamps and marker lamps will illuminate to night intensity.

CONDITIONS FOR CLEARING THE DTC
^ The BCM no longer detects a short to ground in the ambient light sensor signal circuit.
^ A history DTC B2647 will clear after 100 consecutive ignition cycles if the condition for the malfunction is no longer present.
^ Use a scan tool in order to clear the DTC.

DIAGNOSTIC AIDS
^ If the DTC B2647 is a history DTC, the fault may be intermittent. Refer to Testing for Intermittent and Poor Connections.
^ The following conditions may cause an intermittent malfunction to occur:
- An intermittent short to ground in the ambient light signal circuit
- The ambient light sensor is intermittently shorted to ground internally
- The BCM is intermittently shorted to ground internally

TEST DESCRIPTION
The number(s) below refer to the step number(s) on the diagnostic table.
3. Tests for the proper operation of the circuit in the high voltage range.
4. 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.