Circuit Description
The body control module (BCM) uses the ambient light sensor signal in order to control the Daytime Running Lamps (DRL) System. The ambient light sensor is connected to the BCM through the signal circuit and the reference circuit of the ambient light sensor.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC B2645 Ambient Light Sensor Circuit High
Conditions for Running the DTC
| • | Voltage supplied to the module is in the normal operating range approximately 10-16 volts. |
| • | The DRL feature must be enabled. |
Conditions for Setting the DTC
| • | The BCM detects a short to battery positive voltage in the ambient light sensor reference voltage circuit. |
| • | The condition is present for longer than 3 ms. |
Action Taken When the DTC Sets
| • | The BCM stores DTC B2645 in memory. |
| • | The SERVICE VEHICLE SOON telltale illuminates. |
Conditions for Clearing the MIL/DTC
| • | A current DTC B2645 clears when the BCM no longer detects an short to battery positive voltage in the ambient light sensor reference voltage circuit. |
| • | A history DTC B2645 clears after 100 consecutive ignition cycles. |
Diagnostic Aids
| • | If the DTC B2645 is a history DTC, the fault may be intermittent. Refer to Testing for Intermittent Conditions and Poor Connections . |
| • | An intermittent short to battery positive voltage in the following locations may cause an intermittent malfunction to occur: |
| - | The ambient light sensor reference voltage circuit |
| - | The ambient light sensor |
| - | The BCM |
Test Description
The number below refers to the step number on the diagnostic table.
Step | Action | Values | Yes | No |
|---|---|---|---|---|
Schematic Reference: Headlights/Daytime Running Lights (DRL) Schematics Connector End View Reference: Master Electrical Component List | ||||
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | |
Does the voltage measure near the specified value? | 12 V | Go to Step 4 | Go to Step 3 | |
3 | Inspect the ambient light sensor return circuit for a short to battery positive voltage. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 7 | Go to Step 6 |
4 | Inspect the ambient light sensor reference voltage circuit for a short to battery positive voltage. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 7 | Go to Step 5 |
5 | Replace the body control module (BCM). Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 7 | -- |
6 | Replace the ambient light sensor. Refer to Daytime Running Lamp (DRL) Ambient Light Sensor Replacement . Did you complete the replacement? | -- | Go to Step 7 | -- |
7 |
Does the DTC reset? | -- | Go to Step 2 | System OK |
