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 03: Ambient Light Sensor Circuit Voltage Below ThresholdDTC B2645 07: Ambient Light Sensor Circuit Voltage Above Threshold
Diagnostic Fault Information
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
|---|---|---|---|---|
Ambient Light Senor Signal | B2645 03 | B2645 07 | B2645 07 | -- |
Headlamp- Left Low Beam Control | 1 | 1 | 1 | -- |
Headlamp- Right Low Beam Control | 1 | 1 | 1 | -- |
Ambient Light Sensor Low Reference | -- | B2645 07 | B2645 07 | -- |
Headlamp- Right Low Beam Ground | -- | 1 | -- | -- |
Headlamp- Right Low Beam Ground | -- | 1 | -- | -- |
1. Headlamps Malfunction | ||||
Circuit/System Description
The ambient light/sun load 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 5-volt reference signal to the ambient light sensor and the HVAC control module provides a low reference ground. The BCM monitors the ambient light sensor signal circuit to determine if outside lighting conditions are correct for automatic lamp control (ALC) when the headlamp switch is in the AUTO position. In daylight conditions the BCM will command the low beam headlamps OFF. During low light conditions the BCM will command the low beam headlamps ON.
Conditions for Running the DTC
Battery voltage must be between 9-16 volts.
Conditions for Setting the DTC
B2645 03
The BCM detects a short to ground in the ambient light sensor signal circuit.
B2645 07
The BCM detects a short to voltage or an open/high resistance 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
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 sunload sensor.
- Ignition ON, verify that a test lamp illuminates between the low reference circuit terminal C and B+.
- 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 D and the low reference circuit terminal C. Verify the scan tool Ambient Light Sensor parameter is less than 0.196 volts.
- If all circuits test normal, replace the sunload sensor assembly.
| ⇒ | If the test lamp does not illuminate, test the low reference circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the HVAC control module. |
| ⇒ | 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, setup, and programming |
