Cruze

DTC B0173, B0178, or B3933

The air temperature sensors are 2-wire negative temperature co-efficient thermistors. The vehicle uses the following air temperature sensors:

A signal and low reference circuit enables the sensor to operate. As the air temperature surrounding the sensor increases, the sensor resistance decreases. The sensor signal voltage decreases as the resistance decreases. The sensor operates within a temperature range between -40 to +85°C (-40 to +185°F). The sensor signal varies between 0-5 V. The HVAC control module converts the signal to a range between 0-255 counts. As the air temperature increases the count value will decrease. If the HVAC control module detects a malfunctioning sensor, then the control module software will use a default air temperature value. The default action ensures that the HVAC system can adjust the inside air temperature near the desired temperature until the condition is corrected.

The HVAC control module detects the sensor signal out of range. The signal voltage is less than 0.1 V or greater than 4.9 V for more than 50 ms.

The system operates using a default value.

The sensor signal is within specified range between 0.1-4.9 V.

Schematic Reference

HVAC Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Automatic HVAC Description and Operation

Electrical Information Reference

Scan Tool Reference

Control Module References for scan tool information

1. Verify that no DTC is set.

⇒	If a DTC is present, refer to Circuit/System Testing.

2. Measure actual temperature using a thermometer at each of the duct temperature sensors. Compare this value to the appropriate scan tool Duct Actual parameter. The measured temperature should be within 5°C (9°F) difference of appropriate Duct Actual parameter value.

⇒	If not within the specified range, replace the appropriate duct temperature sensor.

3. Measure actual evaporator temperature using a thermometer. Compare this value to the scan tool A/C Evaporator Temperature Sensor parameter. The measured temperature should be within 5°C (9°F) difference of parameter value.

⇒	If not within the specified range, replace the B39 A/C Evaporator Temperature Sensor.

1. Ignition OFF, disconnect the harness connector at the appropriate temperature sensor.
2. Test for less than 5 Ω between the temperature sensor ground circuit terminal B and ground.

⇒	If greater than the specified value, test the ground circuit for an open/high resistance.

3. Ignition ON, test for 4.8-5.2 V between the signal circuit terminal A and ground.

⇒	If less than the specified range, test the signal circuit for a short to ground or open/high resistance. If the circuit tests normal, replace the K33 HVAC Control Module.

⇒	If greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the K33 HVAC Control Module.

4. If all circuits test normal, replace the temperature sensor and verify the DTC does not reset.

⇒	If the DTC resets, replace the K33 HVAC Control Module.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.