B0173
DTC B0173, B0178, or B3933
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 Instructionsprovides an overview of each diagnostic category.
DTC Descriptors
DTC B0173 02
- Upper Left Duct Air Temperature Sensor Circuit Short to Ground
DTC B0173 05
- Upper Left Duct Air Temperature Sensor Circuit High Voltage/Open
DTC B0178 02
- Lower Left Duct Air Temperature Sensor Circuit Short to Ground
DTC B0178 05
- Lower Left Duct Air Temperature Sensor Circuit High Voltage/Open
DTC B0509 02
- Upper Right Duct Air Temperature Sensor Circuit Short to Ground
DTC B0509 05
- Upper Right Duct Air Temperature Sensor Circuit High Voltage/Open
DTC B0514 02
- Lower Right Duct Air Temperature Sensor Circuit Short to Ground
DTC B0514 05
- Lower Right Duct Air Temperature Sensor Circuit High Voltage/Open
DTC B3933 02
- Air Conditioning Evaporator Temperature Sensor Circuit Short to Ground
DTC B3933 05
- Air Conditioning Evaporator Temperature Sensor Circuit High Voltage/Open
Circuit/System Description
The air temperature sensors are a 2-wire negative temperature co-efficient thermistor. The vehicle uses the following air temperature sensors:
* Air temperature sensor - left upper
* Air temperature sensor - left lower
* Air temperature sensor - right upper
* Air temperature sensor - right lower
* A/C evaporator temperature sensor
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.
Conditions for Running the DTC
* Ignition ON
* The HVAC control module is ON.
Conditions for Setting the DTC
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.
Action Taken When the DTC Sets
The system operates using a default value.
Conditions for Clearing the DTC
The sensor signal is within specified range between 0.1-4.9 V.
Reference Information
Schematic Reference
HVAC Schematics HVAC - Automatic
Connector End View Reference
Component Connector End Views Sunshade - Left (D6I)
Description and Operation
Automatic HVAC Description and Operation HVAC - Automatic
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 Control Module References
Circuit/System Testing
1. Ignition OFF and all vehicle systems OFF, disconnect the harness connector at the appropriate temperature sensor It may take up to 2 minutes for all vehicle systems to power down.
2. Test for less than 10 ohm between the low reference circuit terminal B and ground.
• If 10 ohm or greater
1. Ignition OFF, disconnect the harness connector at the K33 HVAC control module.
2. Test for less than 2 ohm in the low reference circuit end to end.
• If 2 ohm or greater, repair the open/high resistance in the circuit.
• If less than 2 ohm, replace the K33 HVAC control module control module.
• If less than 10 ohm
3. Ignition ON.
4. Verify the appropriate scan tool Temperature Sensor parameter is less than -35°C (-39°F).
• If -35°C (-39°F) or less
1. Ignition OFF, disconnect the harness connector at the K33 HVAC control module.
2. Test for infinite resistance between the signal circuit terminal A and ground.
• If less than infinite resistance, repair the short to ground on the circuit.
• If infinite resistance, replace the K33 HVAC control module.
• If greater than -35°C (-39°F)
5. Install a 3 A fused jumper wire between the signal circuit terminal A and the low reference circuit terminal B.
6. Verify the scan tool temperature sensor parameter is greater than 85°C (185°F).
• If 85°C (185°F) or greater
1. Ignition OFF, disconnect the harness connector at the HVAC control module, ignition ON.
2. Test for less than 1 V between the signal circuit and ground.
• If 1 V or greater, repair the short to voltage on the circuit.
• If less than 1 V
3. Ignition OFF
4. Test for less than 2 ohm in the signal circuit end to end.
• If 2 ohm or greater, repair the open/high resistance in the circuit.
• If less than 2 ohm, replace the K33 HVAC control module.
• If less than 0.1 V
7. Test or replace the temperature sensor.
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the diagnostic procedure.
* HVAC Component Replacement Reference HVAC Component Replacement Reference
* Control Module References Control Module Referencesfor HVAC control module replacement, programming and setup