The ambient air temperature sensor is a variable resistor interfaced to the body control module (BCM). The BCM monitors the ambient air temperature sensor. The ambient air temperature sensor is a 2-wire negative temperature coefficient thermistor. The BCM applies 5 volts to an internal input resistor connected to the signal circuit of the ambient air temperature sensor. The BCM provides the ambient air temperature sensor with a low reference circuit. When the ambient air temperature is cold, the sensor resistance is high and the signal voltage is high. When the ambient air temperature is hot, the sensor resistance is low and the signal voltage is low. The BCM provides the logic for reading the sensor, filtering the data and transmitting the information via the serial data circuit to the driver information center (DIC) for display. The temperature is sent to the IPC in degrees Celsius. The IPC is responsible for displaying the temperature and converting to degrees Fahrenheit if necessary. Two serial data signals are ultimately generated. An unfiltered value and a filtered value for use by the DIC display. The BCM also provides the sensor out-of-range detection and compensates for engine temperature by utilizing vehicle speed and engine off time duration.

The BCM detects that the ambient air temperature sensor voltage is less than 0.4 volt or more than 4.8 volts.

Schematic Reference

Instrument Cluster Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Electrical Information Reference

Scan Tool Reference

Control Module References for scan tool information

1. Ignition OFF, disconnect the harness connector at the ambient air temperature sensor.
2. Ignition OFF, test for less than 1 ohm between the low reference circuit terminal B and ground.

⇒	If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the BCM.

3. Ignition ON, verify the scan tool Ambient Air Temp. Sensor parameter is greater than 4.7 volts.

⇒	If less than the specified range, test the signal circuit terminal A for a short to ground. If the circuit tests normal, replace the BCM.

4. Install a 3-amp fused jumper wire between the signal circuit terminal A and the low reference circuit terminal B. Verify the scan tool Ambient Air Temp. Sensor parameter is less than 0.4 volt.

⇒	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.

5. If all circuits test normal, test or replace the ambient air temperature sensor.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.