Orlando

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 : Automatic

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.

⇓	If no DTC is present

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

⇒	If not within the specified range

Replace the duct temperature sensor.

⇓	If within the specified range

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.

⇓	If within the specified range

4. All OK.

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 5 Ω

Repair the open/high resistance in the circuit.

⇓	If less than 5 Ω

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

⇒	If less than 4.8 V

3.1.	Ignition OFF, disconnect the X3 harness connector at the K33 HVAC Control Module.

3.2.	Test for infinite resistance between the signal circuit and ground.

⇒	If less than infinite resistance, repair the short to ground on the circuit.

⇓	If infinite resistance

3.3.	Test for less than 2 Ω in the signal circuit end to end.

⇒	If 2 Ω or greater, repair the open/high resistance in the circuit.

⇒	If less than 2 Ω, replace the K33 HVAC Control Module.

⇒	If greater than 5.2 V

3.1.	Ignition OFF, disconnect the X3 harness connector at the K33 HVAC Control Module.

3.2.	Ignition ON, test for less than 0.3 V between the signal circuit and ground.

⇒	If greater than 0.3 V, repair the short to voltage on the circuit.

⇒	If less than 0.3 V, replace the K33 HVAC Control Module.

⇓	If within 4.8-5.2 V

4. Replace the temperature sensor and verify the DTC does not reset.

⇒	If DTC resets

Replace the K33 HVAC Control Module.

⇓	If DTC does not reset

5. All OK.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.