Diagnostic Instructions
| • | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. |
| • | Review Strategy Based Diagnosis for an overview of the diagnostic approach. |
| • | Diagnostic Procedure Instructions provides an overview of each diagnostic category. |
DTC Descriptor
DTC B2645 00: Ambient Light Sensor CircuitDiagnostic Fault Information
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
|---|---|---|---|---|
HDM Relay B+ | 2 | 2 | -- | -- |
Ambient Light Sensor Signal | B2645 00 | B2645 00 | B2645 00 | -- |
HDM Relay Control (w/o TT6) | B2575 00 | B2575 00 | B2575 00 | -- |
LO BEAM Relay Control (with TT6) | B2575 00 | B2575 00 | B2575 00 | -- |
Low Beam Headlamp Control | 2 | 2 | 2 | -- |
Ambient Light Sensor Low Reference | 1 | B2645 00 | 1 | -- |
HDM Relay Ground | -- | 2 | -- | -- |
Headlamp Ground | -- | 3 | -- | -- |
1. Daytime Running Lamp Malfunction 2. Headlamp Malfunction - Low Beam 3. Headlamp Switch Malfunction | ||||
Circuit/System Description
The body control module (BCM) monitors the ambient light sensor signal circuit in order to determine if the daytime running lights (DRL) or the auto headlights (ALC) should be turned ON in the AUTO mode. When the BCM senses the ambient light sensor signal voltage is between 1.75-4.9 volts, either the DRL will be commanded ON or the ALC will be commanded ON depending upon the amount of light received by the sensor.
Conditions for Running the DTC
The battery voltage must be between 9-16 volts.
Conditions for Setting the DTC
| • | The ambient light sensor signal voltage is less than 1.75 volts. |
| • | The ambient light sensor signal voltage is greater than 4.9 volts. |
Action Taken When the DTC Sets
ALC will remain ON in any ambient light state.
Conditions for Clearing the DTC
| • | This DTC will clear on current status after the condition for setting the fault is corrected. |
| • | A history DTC will clear after 100 consecutive ignition cycles without a fault present. |
Reference Information
Schematic Reference
Headlights/Daytime Running Lights (DRL) Schematics
Connector End View Reference
Description and Operation
Exterior Lighting Systems Description and Operation
Electrical Information Reference
Scan Tool Reference
Control Module References for scan tool information
Circuit/System Testing
- Ignition OFF, disconnect the harness connector at the ambient light sensor.
- Ignition OFF, test for less than 5.0 ohms between the low reference circuit terminal C and ground.
- Ignition ON, verify the scan tool Light Sensor parameter is greater than 4.9 volts.
- Install a 3A fused jumper wire between the signal circuit terminal D and the low reference circuit terminal C. Verify the scan tool Light Sensor parameter is less than 1.0 volt.
- If all circuits test normal, test or replace the ambient light sensor.
| ⇒ | If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the BCM. |
| ⇒ | If less than the specified range, test the signal circuit terminal D for a short to ground. If the circuit tests normal, replace the BCM. |
| ⇒ | If greater than the specified range, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the BCM. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
| • | Control Module References for BCM replacement, programming, and setup |
