Diagnostic Instructions

DTC Descriptors

DTC B0173 02: Output Air Temperature Sensor 1 Circuit Short to Ground

DTC B0173 05: Output Air Temperature Sensor 1 Circuit Short to Battery or Open

DTC B0178 02: Output Air Temperature Sensor 2 Circuit Short to Ground

DTC B0178 05: Output Air Temperature Sensor 2 Circuit Short to Battery or Open

DTC B0509 02: Output Air Temperature Sensor 3 Circuit Short to Ground

DTC B0509 05: Output Air Temperature Sensor 3 Circuit Short to Battery or Open

DTC B0514 02: Output Air Temperature Sensor 4 Circuit Short to Ground

DTC B0514 05: Output Air Temperature Sensor 4 Circuit Short to Battery or Open

Diagnostic Fault Information

Circuit	Short to Ground	Open/High Resistance	Short to Voltage	Signal Performance
Upper Left Air Temperature Sensor Signal	B0173 02	B0173 05	B0173 05	--
Upper Right Air Temperature Sensor Signal	B0509 02	B0509 05	B0509 05	--
Lower Left Air Temperature Sensor Signal	B0178 02	B0178 05	B0178 05	--
Lower Right Air Temperature Sensor Signal	B0514 02	B0514 05	B0514 05	--
Low Reference	--	B0173 05, B0158 05, B0163 05, B0509 05, B0178 05, B0514 05, B3933 05	B0173 05, B0158 05, B0163 05, B0509 05, B0178 05, B0514 05, B3933 05	--

Circuit/System Description

The HVAC control module supplies the air duct temperature sensors with a low reference circuit and 5-volt 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.

Conditions for Running the DTC

The ignition is turned ON.

Conditions for Setting the DTC

The HVAC control module detects the inside air temperature sensor signal circuit is less than -36°C (-38°F) or greater than 215°C (419°F) for greater than 15 seconds.

Action Taken When the DTC Sets

The system operates using a default value.

Conditions for Clearing the DTC

Reference Information

Schematic Reference

HVAC Schematics

Connector End View Reference

HVAC Connector End Views

Description and Operation

Electrical Information Reference

Scan Tool Reference

Circuit/System Verification

Ignition ON, observe the appropriate scan tool air duct temperature sensor. The reading should be between -35°C (-39°F) and 98°C (208°F) and change with duct air temperature changes.

Circuit/System Testing

Important: If an air duct temperature sensor has an out of range condition caused by a short to voltage, short to ground, or an open/high resistance, the scan tool will display the same value: 39°F (4°C).

1. Ignition OFF, disconnect the harness connector at the appropriate air duct temperature sensor.
2. Ignition OFF, test for less than 10 ohms between the low reference circuit terminal 2 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, test for 4.8-5.2 volts between the signal circuit terminal 1 and the low reference circuit terminal 2 .

⇒	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 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 HVAC control module.

4. If all circuits test normal, test or replace the air duct temperature sensor.

Component Testing

1. Test the air duct temperature sensor by varying the sensor temperature while monitoring the sensor resistance.
2. Compare the readings with the Sensor Resistance Table and verify that the resistance is within 5 percent of the specification.

⇒	If not within the specified range, replace the sensor.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.