Circuit Description
The body control module (BCM) monitors the daytime running lamps (DRL) ambient light sensor signal circuit in order to determine if the DRL or the headlamps should be turned ON in the automatic lamp control (ALC) mode. When the BCM senses the ambient light sensor voltage is between 1-4.9 volts, either the DRL or the headlamps will be commanded ON.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC B2645 Ambient Light Sensor Circuit
Conditions for Running the DTC
The system voltage must be between 9-16 volts.
Conditions for Setting the DTC
| • | When the DRL ambient light sensor signal voltage is less than 1 volt |
| • | When the DRL ambient light sensor signal voltage is more than 4.9 volts |
Action Taken When the DTC Sets
The headlamps will remain ON in any ambient light state during ALC mode.
Conditions for Clearing the MIL/DTC
| • | This DTC will clear immediately after the condition for setting the fault is corrected. |
| • | A history DTC will clear after 100 consecutive ignition cycles without a fault present. |
| • | History and current DTCs can be cleared using a scan tool. |
Step | Action | Value(s) | 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 | |
2 |
Does the scan tool indicate that the Ambient Light Sensor parameter is within the specified range? | 1-4.9 V | Go to Testing for Intermittent Conditions and Poor Connections | Go to Step 3 |
3 |
Does the scan tool indicate that the ambient light sensor parameter is less than the specified value? | 5 V | Go to Step 4 | Go to Step 5 |
4 | Test the daytime running lamps (DRL) ambient light sensor signal circuit of the ambient light sensor for a short to ground. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 10 | Go to Step 7 |
5 | Test the DRL ambient light sensor signal circuit of the ambient light sensor for a short to voltage or an open/high resistance. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 10 | Go to Step 6 |
6 | 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 10 | Go to Step 8 |
7 | 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 10 | Go to Step 9 |
8 | Replace the ambient light sensor. Refer to Daytime Running Lamp (DRL) Ambient Light Sensor Replacement . Did you complete the replacement? | -- | Go to Step 10 | -- |
9 | Replace the BCM. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 10 | -- |
10 |
Does the DTC reset? | -- | Go to Step 2 | System OK |
