B2648

CIRCUIT DESCRIPTION
The body control module (BCM) uses the DRL ambient light sensor signal to control the automatic headlamp system. The DRL ambient light sensor is connected directly to the BCM through the DRL ambient light sensor signal circuit and the DRL ambient light low reference circuits.

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 that the DRL ambient light sensor signal circuit is greater than 4 volts or is open when it is trying to enable the automatic headlamp control feature.
^ The condition above must be present for more than 0.3 seconds.

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

CONDITIONS FOR CLEARING THE DTC
^ The BCM no longer detects the fault in the DRL ambient light sensor signal.
^ A history DTC B2648 will clear after 100 consecutive ignition cycles if the condition for the malfunction is no longer present.

DIAGNOSTIC AIDS
^ If the DTC B2648 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 open in DRL ambient light sensor signal circuit
- The DRL ambient light sensor is intermittently open internally.
- The BCM is intermittently open internally.

TEST DESCRIPTION

Steps 1-3:

Steps 4-12:

The numbers below refer to the step numbers 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.