Diagnostic Instructions

DTC Descriptor

DTC B0163 05: Passenger Compartment Temp Sensor Circuit Short to Battery or Open

DTC B0163 06: Passenger Compartment Temp Sensor Circuit Short to Ground or Open

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

DTC B0173 06: Output Air Temperature Sensor Circuit Short to Ground or Open

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

DTC B0178 06: Output Air Temperature Sensor 2 Circuit Short to Ground

Diagnostic Fault Information

Circuit	Short to Ground	Open/High Resistance	Short to Voltage	Signal Performance
Upper Air Temperature Sensor Signal	B0173 06	B0173 05, B0173 06	B0173 05
Lower Air Temperature Sensor Signal	B0173 06	B0173 05, B0173 06	B0178 05
Low Reference		B0173 05, B0178 05, B0163 05	B0173 05, B0178 05, B0163 05

Circuit/System Description

Air temperature sensors allow the HVAC control module to monitor the temperature of the discharge air in the HVAC ducts. The module applies 5 volts to internal input resistors that are connected to the signal circuits of the air temperature sensors. The module provides ground to the air temperature sensors through the low reference circuit. The HVAC control module monitors the voltage drops across the air temperature sensors and uses the inputs for automatic control calculations. When the duct air temperatures are cold, the resistances of the sensors are high and the voltage signals are high. When the duct air temperatures are hot, the resistances of the sensors are low and the voltage signals are low. The HVAC control module converts the voltage values to count values where one volt is approximately equal to 51 counts.

B0163

This DTC is for the passenger compartment air temperature sensor.

B0173

This DTC is for the upper air temperature sensor.

B0178

This DTC is for the lower air temperature sensor.

Conditions for Running the DTC

The ignition is ON.

Conditions for Setting the DTC

The HVAC control module detects the air temperature sensor signal circuit is less than 0.09 volts (5 counts) or more than 4.90 volts (250 counts).

Action Taken When the DTC Sets

The Auto feature of the HVAC control module will be inoperative.

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 Testing

1. Ignition OFF, disconnect the harness connector at the appropriate temperature sensor.
2. Ignition OFF, test for less than 1.0 ohm between the appropriate low reference circuit terminal B and ground.

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

3. Ignition ON, verify the appropriate scan tool temperature sensor parameter is greater than 250 counts.

⇒	If less than the specified range, test the appropriate signal circuit terminal for a short to ground. If the circuit tests normal, replace the HVAC control module.

4. Install a 3A fused jumper wire between the appropriate signal circuit terminal A and ground. Verify the appropriate scan tool temperature sensor parameter is less than 5 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, test or replace the appropriate temperature sensor.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.