Component Tests and General Diagnostics

Ambient Air Temperature Malfunction

Diagnostic Instructions

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

Diagnostic Fault Information






Circuit/System Description

The HVAC control module supplies the ambient air temperature sensor with a low reference circuit and signal circuit. The HVAC control module determines the voltage drop across the sensor, which is proportional to temperature. As the air temperature increases, the sensor resistance decreases and the voltage signal decreases. As the air temperature decreases, the sensor resistance increases and the voltage signal increases.

Reference Information

Schematic Reference
HVAC Schematics Electrical Diagrams

Connector End View Reference
HVAC Connector End Views Connector Views

Description and Operation
Air Temperature 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
- Scan Tool Data List Scan Tool Testing and Procedures
- Scan Tool Output Controls Scan Tool Testing and Procedures
- Scan Tool Data Definitions Scan Tool Testing and Procedures

Circuit/System Testing

Important: An instant OAT update must be performed by pressing the A/C and Recirc buttons at the same time after the system has been repaired to convert the A/C permission from out of range to normal.

1. Ignition OFF, disconnect the harness connector at the outside air temperature sensor.
2. Ignition OFF, test for less than 10 ohms of resistance 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 HVAC control module.
3. Ignition ON, verify the scan tool Ambient Air Temperature sensor parameter is less than -35°F (-37°C).
- If greater than the specified range, test the signal circuit terminal A for a short to ground. If the circuit tests normal, replace the HVAC control module.
4. Install a 3A fused jumper wire between the signal circuit terminal A and the low reference circuit terminal B. Verify the scan tool Ambient Air Temperature sensor parameter is greater than 180°F (82°C).
- If less 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 HVAC control module.
5. If all circuits test normal, test or replace the ambient air temperature sensor.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure Programming and Relearning.
Control Module References for HVAC control module replacement, setup and programming Programming and Relearning.
Ambient Air Temperature Sensor Replacement.