Outside Air Temperature Display Inaccurate or Inoperative

Outside Air Temperature Display Inaccurate or Inoperative

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle (Initial Inspection and Diagnostic Overview) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Initial Inspection and Diagnostic Overview) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Initial Inspection and Diagnostic Overview) provides an overview of each diagnostic category.

Diagnostic Fault Information





Circuit/System Description

The ambient air temperature sensor is a variable resistor interfaced to the underhood electrical center (UEC). The ambient air temperature sensor is a 2-wire negative temperature coefficient thermistor. The UEC applies voltage to an internal input resistor connected to the signal circuit of the ambient air temperature sensor. 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 UEC 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.

Reference Information
Schematic Reference

Instrument Cluster Schematics (Instrument Cluster Schematics)
Connector End View Reference

Component Connector End Views (Connector Views)
Description and Operation

* Instrument Cluster Description and Operation (Description and Operation)
* Driver Information Center (DIC) Description and Operation (Description and Operation)

Electrical Information Reference

* Circuit Testing (Component Tests and General Diagnostics)
* Connector Repairs (Component Tests and General Diagnostics)
* Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics)
* Wiring Repairs (Component Tests and General Diagnostics)

Scan Tool Reference

Control Module References (Programming and Relearning) for scan tool information

Circuit/System Testing

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

• If greater than the specified range, test the ground circuit for an open/high resistance. If the circuit tests normal, replace the ECM.

3. Ignition ON, verify the scan tool Ambient Air Temp. Sensor parameter is approximately -40°C (-40°F).

• If greater than the specified value, test the signal circuit terminal 1 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 1 and ground. Verify the scan tool Ambient Air Temp. Sensor parameter is approximately 87°C (188°F).

• If less than the specified value, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the UEC.

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

Repair Instructions

Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.

* Ambient Air Temperature Sensor Replacement (Service and Repair)
* Control Module References (Programming and Relearning) for UEC replacement, setup, and programming.