B2645

DTC B2645

Circuit Description

The HVAC control module determines the ambient light conditions, DAY or NIGHT, based on the voltage from the ambient light sensor. The HVAC control module provides the ambient light sensor with a 5-volt reference voltage and a signal return circuit. The ambient light sensor signal circuit is a direct input to the HVAC control module. The HVAC control module sends a message via GMLAN serial data to the instrument panel module (IPM) indicating the outside light conditions based on the signal from the ambient light sensor. For more detailed information concerning interior lighting operation, refer to Interior Lighting Systems Description and Operation.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC B2645 Ambient Light Sensor Circuit





Conditions for Running the DTC

* The HVAC control module must be powered.
* DTC B1327 Battery Voltage Low, must not be current.

Conditions for Setting the DTC

Ambient light sensor voltage is less than 0.09 volts or greater than 4.75 volts on 3 consecutive tests.

Action Taken When the DTC Sets

* The ambient light sensor will default to NIGHT status.
* The HVAC control module commands the Service A/C System indicator ON via GMLAN serial data.

Conditions for Clearing the DTC

* The condition responsible for setting the DTC no longer exists.
* You issue a scan tool CLEAR DTCs command.
* A history DTC will clear once 40 consecutive malfunction-free ignition cycles have occurred.

Diagnostic Aids

Thoroughly inspect the wiring and connectors. An incomplete inspection of the wiring and connectors may result in misdiagnosis causing part replacement with the reappearance of the malfunction. If an intermittent malfunction exists, refer to Testing for Intermittent Conditions and Poor Connections. Component Tests and General Diagnostics

Test

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