Circuit Description
The body control module (BCM) uses the ambient light sensor signal to control the daytime running lamps. The ambient light sensor is connected directly to the BCM.
Conditions for Running the DTC
| • | The system voltage must be between 9 and 16 volts. |
| • | The ignition switch must be in the RUN position. |
| • | The park brake must be released. |
| • | The headlamp switch must be in the AUTO position. |
| • | The DRL feature must be enabled. |
Conditions for Setting the DTC
| • | When the ambient light sensor input voltage is greater than 4.78 volts. |
| • | The courtesy lamp relay coil control circuit is shorted to the battery. |
| • | The above conditions must be met for 0.5 seconds. |
Action Taken When the DTC Sets
| • | The daytime running lamps will remain ON. |
| • | The BCM stores DTC B2648 in memory. |
| • | Exterior lamps illuminate to low light intensity. |
Conditions for Clearing the MIL/DTC
| • | A current DTC B2648 clears when the BCM no longer detects the fault in the signal circuit or the low reference circuit of the DRL ambient light sensor. |
| • | A history DTC B2648 clears after 100 consecutive ignition cycles. |
| • | The BCM receives the Clear Code command from the scan tool. |
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. |
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 | |
2 |
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 |
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 |
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 |
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 |
Does the DTC reset? | -- | Go to Step 2 | System OK |
