B0173
DTC B0163, B0173, or B0178
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle (Diagnostic System Check - Vehicle) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Strategy Based Diagnosis) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Diagnostic Procedure Instructions) provides an overview of each diagnostic category.
DTC Descriptors
DTC B0163 05
- Passenger Compartment Temperature Sensor Circuit Short to Battery or Open
DTC B0163 06
- Passenger Compartment Temperature Sensor Circuit Short to Ground or Open
DTC B0173 05
- Upper Air Temperature Sensor 1 Circuit Short to Battery or Open
DTC B0173 06
- Upper Air Temperature Sensor 1 Circuit Short to Ground or Open
DTC B0178 05
- Lower Air Temperature Sensor 2 Circuit Short to Battery or Open
DTC B0178 06
- Lower Air Temperature Sensor 2 Circuit Short to Ground or Open
Diagnostic Fault Information
Circuit/System Description
Inside Air Temperature Sensor
The inside air temperature sensor is internal to the HVAC control module.
Upper and Lower Air Duct Temperature Sensors
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
Ignition ON.
Conditions for Setting the DTC
The HVAC control module detects the air temperature sensor signal circuit is less than 5 counts or greater than 250 counts.
Action Taken When the DTC Sets
The Auto feature of the HVAC control module will be inoperative.
Conditions for Clearing the DTC
* The DTC will become history if the HVAC control module no longer detects a failure.
* The history DTC will clear after 100 fault-free ignition cycles.
Reference Information
Schematic Reference
HVAC Schematics (HVAC - Automatic)
Connector End View Reference
Component Connector End Views (Connector End Views By Name)
Description and Operation
* Air Temperature Description and Operation (Air Temperature)
* Air Delivery Description and Operation (Air Delivery)
Electrical Information Reference
* Circuit Testing (Circuit Testing)
* Connector Repairs (Connector Repairs)
* Testing for Intermittent Conditions and Poor Connections (Testing for Intermittent Conditions and Poor Connections)
* Wiring Repairs (Wiring Repairs)
Scan Tool Reference
Control Module References (Programming and Relearning) for scan tool information
Circuit/System Verification
B1063
Verify DTC B1063 is not set.
If the DTC is set, replace the HVAC control module.
B0173 or B0178
Ignition ON, observe the appropriate scan tool Duct Air Temp. Sensor parameter. The reading should be between 5-250 counts and change with inside passenger compartment or upper or lower air duct air temperature changes.
Circuit/System Testing
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 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 that both the appropriate scan tool Duct Air Temp. Sensor parameter is less than 5 counts.
• If greater 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 3A fused jumper wire between the signal circuit terminal A and the low reference circuit terminal B. Verify the appropriate scan tool Duct Air Temp. Sensor parameter is greater than 250 counts.
• If less 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 air temperature sensor.
Component Testing
1. A thermometer can be used to test the sensor off the vehicle in warm and or cold water. Refer to Sensor Resistance Table ([1][2]Electrical Specifications) for this test.
2. Test the ambient air temperature sensor by varying the sensor temperature while monitoring the sensor resistance.
3. Compare the readings with the Temperature vs 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 (Verification Tests) after completing the diagnostic procedure.
* Duct Air Temperature Sensor Replacement - Upper (Duct Air Temperature Sensor Replacement - Upper)
* Duct Air Temperature Sensor Replacement - Lower (Duct Air Temperature Sensor Replacement - Lower)
* Control Module References (Programming and Relearning) for HVAC control module replacement, setup, and programming