Circuit Description
The Body Control Module (BCM) uses the ambient light sensor signal to control the automatic headlamp control system and the Daytime Running Lamps (DRL). The ambient light sensor is connected directly to the BCM through the DRL ambient light sensor signal circuit and the DRL ambient light low reference circuit.
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 a short to ground in the DRL ambient light sensor signal circuit. |
| • | The ambient light sensor is internally shorted. |
| • | The condition above must be present for more than 0.3 seconds. |
Action Taken When the DTC Sets
| • | The BCM stores DTC B2647 in memory. |
| • | The DRL will default to night mode and the headlamps, park lamps, tail lamps and side marker lamps will illuminate. |
Conditions for Clearing the DTC
| • | The BCM no longer detects a short to ground in the DRL ambient light sensor signal circuit. |
| • | A history DTC B2647 will clear after 100 consecutive ignition cycles if the condition for the malfunction is no longer present. |
| • | The BCM receives a clear code command from the scan tool. |
Diagnostic Aids
| • | If the DTC B2647 is a history DTC, the fault may be intermittent. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems. |
| • | The following conditions may cause an intermittent malfunction to occur: |
| - | An intermittent short to ground in the DRL ambient light sensor signal circuit |
| - | The ambient light sensor is intermittently shorted. |
| - | The BCM is intermittently shorted to ground. |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
Tests for the proper operation of the circuit in the high voltage range.
-
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 battery positive voltage.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
Schematic Reference: Exterior Lights Schematics Connector End View Reference: Master Electrical Component List in Wiring Systems | ||||
1 | Did you perform the Lighting System Diagnostic System Check? | -- | Go to Step 2 | |
2 |
Does the scan tool indicate that the ambient light sensor input parameter is within the specified range? | 0.25-2.5 V | Go to Diagnostic Aids | Go to Step 3 |
Does the scan tool indicate that the ambient light sensor input parameter is greater than the specified value? | 2.5 V | Go to Step 4 | Go to Step 5 | |
Does the scan tool indicate that the ambient light sensor input parameter is less than the specified value? | 0.25 V | Go to Step 8 | Go to Step 6 | |
5 | Test the DRL ambient light sensor signal circuit of the ambient light sensor for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 9 |
6 | Test the DRL ambient light sensor low reference circuit of the ambient light sensor for a high resistance, an open, or short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 7 |
7 | Test the DRL ambient light sensor signal circuit of the ambient light sensor for a short to battery positive voltage, 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 12 | Go to Step 9 |
8 | 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 12 | Go to Step 10 |
9 | Inspect for poor connections at the harness connector of the Body Control Module (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 12 | Go to Step 11 |
10 | Replace the ambient light sensor. Refer to Daytime Running Lamp (DRL) Ambient Light Sensor Replacement . Did you complete the replacement? | -- | Go to Step 12 | -- |
11 |
Important: Perform the set up procedure for the Body Control Module (BCM). Refer to Body Control Module (BCM) Programming/RPO Configuration in Body Control System. Replace the BCM. Refer to Body Control Module Replacement in Body Control System. Did you complete the replacement? | -- | Go to Step 12 | -- |
12 |
Does the DTC reset? | -- | Go to Step 2 | System OK |
