Circuit Description
The body control module (BCM) uses the daytime running lamps (DRL) ambient light sensor signal circuit to control the automatic headlamp control system. The ambient light sensor is connected directly to the BCM through the DRL ambient light sensor signal circuit and through the DRL ambient light sensor low reference circuit.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC B2647 Ambient Light Sensor Circuit Low
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 shorted internally. |
| • | The condition above must be present for more than 5 seconds. |
Action Taken When the DTC Sets
| • | The BCM stores DTC B2647 in memory. |
| • | The headlamps, park lamps, tail lamps, and marker lamps will illuminate to low light intensity. |
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 condition is no longer present. |
| • | The BCM receives the 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 . |
| • | The following conditions may cause an intermittent condition to occur: |
| - | An intermittent short to ground in the DRL ambient light sensor signal circuit |
| - | The ambient light sensor is intermittently shorted to ground. |
| - | The BCM is intermittently shorted to ground. |
Step | Action | Values | Yes | No |
|---|---|---|---|---|
Schematic Reference: Interior Lights Schematics Connector End View Reference: Master Electrical Component List | ||||
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | 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 |
3 |
Does the scan tool indicate that the ambient light sensor input parameter is less than the specified value? | 0.25 V | Go to Step 5 | Go to Step 4 |
4 |
Does the scan tool indicate that the Ambient Light Sensor Input parameter is less than the specified value? | 0.25 V | Go to Step 7 | Go to Step 6 |
5 | Test the DRL ambient light sensor signal circuit for a short to ground. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 11 | Go to Step 8 |
6 | Test the DRL ambient light sensor signal circuit for a high resistance or an open. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 11 | Go to Step 8 |
7 | 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 . Did you find and correct the condition? | -- | Go to Step 11 | Go to Step 9 |
8 | Inspect for poor connections at the harness connector of the BCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | -- | Go to Step 11 | Go to Step 10 |
9 | Replace the ambient light sensor. Refer to Ambient Light Sensor Replacement . Did you complete the replacement? | -- | Go to Step 11 | -- |
10 | Replace the BCM. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 11 | -- |
11 |
Does the DTC set again? | -- | Go to Step 2 | System OK |
