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 Descriptors
DTC B2645 02: Ambient Light Sensor Circuit Short to GroundDTC B2645 05: Ambient Light Sensor Circuit Short to Battery or Open
Diagnostic Fault Information
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
|---|---|---|---|---|
DRL Relay B+ | 2 | 2 | 2 | -- |
Ambient Light Sensor Signal | B2645 02 | B2645 05 | B2645 05 | -- |
Daytime Running Lamps Relay Control | 2 | 2 | 2 | -- |
Daytime Running Lamps Control | 2 | 2 | 2 | -- |
Headlamp - Left Front Low Beam Control | 1 | 1 | 1 | -- |
Headlamp - Right Front Low Beam Control | 1 | 1 | 1 | -- |
Ambient Light Sensor Low Reference | -- | 2 | 2 | -- |
Headlamp - Left Front Ground | -- | 1 | -- | -- |
Headlamp - Right Front Ground | -- | 1 | -- | -- |
1. Headlamps Malfunction 2. Daytime Running Lamps Malfunction | ||||
Circuit/System Description
The ambient light sensor is used to monitor outside lighting conditions. The ambient light sensor provides a voltage signal that will vary between 0.2 and 4.9 volts depending on outside lighting conditions. The body control module (BCM) provides a low reference ground and 5-volt reference signal to the ambient light sensor. The BCM monitors the ambient light sensor signal circuit to determine if outside lighting conditions are correct for either daytime running lights (DRL) or automatic lamp control (ALC) when the headlamp switch is in the AUTO position. In daylight conditions the BCM will command the DRLs ON. During low light conditions the BCM will command the low beam headlamps ON. Any function or condition that turns on the headlamps will cancel DRL operation.
Conditions for Running the DTC
Battery voltage must be between 9-16 volts.
Conditions for Setting the DTC
B2645 02
The DTC will set when the BCM detects a short to ground in the ambient light sensor signal circuit.
B2645 05
The DTC will set when the BCM detects a short to voltage or an open in the ambient light sensor signal circuit.
Actions Taken When the DTC Sets
| • | Automatic lamp control (ALC) is inoperative. |
| • | The BCM defaults to low light status and commands the low beam headlamps ON. |
Conditions for Clearing the DTC
| • | The condition responsible for setting the DTC no longer exists. |
| • | A history DTC will clear once 100 consecutive malfunction-free ignition cycles have occurred. |
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, scan tool OFF, doors CLOSED, test for less than 10 ohms between the low reference circuit terminal B and ground.
- Ignition ON, verify the scan tool Ambient Light Sensor parameter is greater than 4.65 volts.
- Install a 3 A fused jumper wire between the signal circuit terminal A and the low reference circuit terminal B. Verify the scan tool Ambient Light Sensor parameter is less than 0.196 volts.
- If all circuits test normal, replace the ambient light sensor.
| ⇒ | If greater than the specified range, test the low reference circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the BCM. |
| ⇒ | If less than the specified range, test the signal circuit terminal A for a short to ground or an open/high resistance. If the circuit tests normal, replace the BCM. |
| ⇒ | If greater than the specified range, test the signal circuit for a short to voltage. 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, setup, and programming |
