B2648

DTC B2648 Ambient Sensor Circuit High:

DTC B2648 Ambient Light Sensor Circuit High:

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

CONDITIONS FOR SETTING THE DTC
^ When the ambient light sensor input voltage is greater than 4.78 volts (CKT 278 is shorted to the battery).
^ 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 corrected.
^ A history DTC will clear after 100 consecutive ignition cycles without a fault present.
^ Use a scan tool in order to clear history and current DTCs.

DIAGNOSTIC AIDS
^ Always perform the first DTC listed on the scan tool if more than 1 is displayed.
^ The scan tool must display DTC B2648 as a current code to 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.
2. This step determines if the ambient light sensor is shorted internally.
3. This step determines if the BCM is defective or if CKT 278 is short to battery voltage. By disconnecting the BCM connector, other DTCs will be set.