Diagnostic Aids

If the DTC B2648 is a history DTC, the fault may be intermittent. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.
An intermittent short to voltage or an open in the following locations may cause an intermittent malfunction to occur:
- The low reference circuit of the DRL ambient light sensor.
- The sensor circuit of the DRL ambient light sensor.
- The ambient light sensor.
- The BCM.

DTC B2648

Step	Action	Value(s)	Yes	No
Schematic Reference: Headlights/Daytime Running Lights (DRL) Schematics Connector End View Reference: Master Electrical Component List in Wiring Systems.
1	Did you perform the Lighting Systems Diagnostic System Check?	-	Go to Step 2	Go to Diagnostic System Check - Lighting Systems
2	Install a scan tool. Turn ON the ignition, with the engine OFF. With a scan tool, observe the ambient light sensor parameter in the Body Control Module (BCM) data list. Does the scan tool indicate that the ambient light sensor parameter is within the specified range?	0.2-4.7 V	Go to Diagnostic Aids	Go to Step 3
3	Turn OFF the ignition. Disconnect the ambient light sensor. Turn ON the ignition, with the engine OFF. With a scan tool, observe the ambient light sensor parameter. Does the scan tool indicate that the ambient light sensor parameter is less than the specified value?	0.02 V	Go to Step 4	Go to Step 9
4	Turn OFF the ignition. Connect a 3-amp fused jumper wire between the low reference circuit of the ambient light sensor and the signal circuit of the ambient light sensor. Turn ON the ignition, with the engine OFF. With a scan tool, observe the ambient light sensor parameter. Does the scan tool indicate that the ambient light sensor parameter is greater than the specified value?	4.7 V	Go to Step 5	Go to Step 7
5	Disconnect the fused jumper wire. Measure the voltage between the low reference circuit of the ambient light sensor and the signal circuit of the ambient light sensor. Does the voltage measure less than the specified value?	5.25 V	Go to Step 10	Go to Step 6
6	Test the low reference circuit of the ambient light sensor for a short to battery positive voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition?	-	Go to Step 14	Go to Step 11
7	Test the low reference circuit of the ambient light sensor for a short to ground, a high resistance, or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition?	-	Go to Step 14	Go to Step 8
8	Test the signal circuit of the ambient light sensor for a short to ground, a high resistance, or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition?	-	Go to Step 14	Go to Step 11
9	Test the ambient light sensor signal circuit for a short to battery positive voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition?	-	Go to Step 14	Go to Step 11
10	Inspect for poor connections at the harness connector of the ambient light sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition?	-	Go to Step 14	Go to Step 12
11	Inspect for poor connections at the harness connector of the BCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition?	-	Go to Step 14	Go to Step 13
12	Replace the ambient light sensor. Refer to Ambient Light Sensor Replacement . Did you complete the replacement?	-	Go to Step 14	-
13	IMPORTANT: Perform the setup procedure for the BCM. Refer to Body Control Module (BCM) Programming/RPO Configuration in Body Control System. Replace the body control module (BCM). Refer to Body Control Module Replacement in Body Control System.Did you complete the replacement?	-	Go to Step 14	-
14	Use the scan tool in order to clear the DTCs. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text. Does the DTC reset?	-	Go to Step 2	System OK