B2647

DTC B2647 Ambient Sensor Circuit Low:

DTC B2647 Ambient Light Sensor Circuit Low:

CIRCUIT DESCRIPTION
The Body Control Module (BCM) monitors CKT 278 in order to determine if the Daytime Running Lights (DRL) or the Auto Headlights (AHL) should be turned ON in the AUTO mode. When the BCM senses the ambient light sensor voltage between 1.7-4.7 volts (light state) the DRL will be commanded ON. When the BCM senses the ambient light sensor voltage between 0.2-1.0 volts (park state) the AHL will be commanded.

CONDITIONS FOR SETTING THE DTC
^ When the ambient light sensor input voltage is less than 0.2 volts (CKT 278 is open or shorted to ground).
^ The system voltage must be between 9.0-16.0 volts.
^ The above conditions must be met for 0.5 seconds.

ACTION TAKEN WHEN THE DTC SETS
The AHL will remain ON in any ambient light state.

CONDITIONS FOR CLEARING THE MIL/DTC
^ This DTC will clear immediately after the condition for setting the fault is corrected.
^ A history DTC will clear after 100 consecutive ignition cycles without a fault present.
^ Use a scan too in order to clear history and current DTCs.

DIAGNOSTIC AIDS
^ Always perform the first DTC listed on the scan tool if more than 1 DTC is displayed.
^ The scan tool must display DTC B2647 as a current code before performing diagnostics.
^ Perform a visual inspection for loose or poor connections at all related components.

TEST DESCRIPTION
Step number(s) below refer to the same step number(s) in the Diagnostic Table.
3. This step tests the ambient light sensor CKT 278 for an open.
4. This step tests the ambient light sensor CKT 278 for a short to ground.