The HVAC control module monitors the evaporator temperature via the evaporator temperature sensor. When the air is cold, the sensor resistance and signal voltage are high. When the air is warm, the sensor resistance and signal voltage are low.

The ignition is turned ON.

The HVAC control module detects the evaporator temperature sensor signal circuit is less than 0.443 volt or greater than 4.55 volts.

The air conditioning (A/C) compressor will be disabled.

Schematic Reference

HVAC Schematics

Connector End View Reference

HVAC Connector End Views

Description and Operation

Electrical Information Reference

Scan Tool Reference

1. Ignition OFF, disconnect the harness connector at the evaporator temperature sensor.
2. Test for less than 1.0 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 HVAC control module.

3. Ignition ON, verify A/C EVAP. Temperature Sensor parameter is greater than 250 counts.

⇒	If less 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 3-amp fused jumper wire between the signal circuit terminal A and the low reference circuit terminal B. Verify the scan tool A/C Evap. Temperature Sensor parameter is less than 3 counts.

⇒	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 HVAC control module.

5. If all circuits test normal, replace the evaporator temperature sensor.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for HVAC control module replacement, setup, and programming