Buick Regal: DTC B0173, B0178, B0509, B0514 or B3933
Diagnostic Instructions
- Perform the Diagnostic System Check - Vehicle prior to using this
diagnostic procedure.
- Review Strategy Based Diagnosis for an overview of the diagnostic
approach.
- Diagnostic Procedure Instructions provides 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
Diagnostic Fault Information
Circuit/System Description
The air temperature sensors are a 2-wire negative temperature coefficient
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
This sensor operates using signal and low reference circuits. As the air
temperature surrounding the
sensor increases, the sensor resistance decreases. The sensor is capable of
reading temperatures ranging
from -40 to +115ºC (-40 to +240ºF), with a signal voltage between 0 - 5 V. If
the HVAC control
module detects a malfunctioning sensor the software uses 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 Wiring Schematics
Connector End View Reference
Component Connector End View Index
Description and Operation
Automatic HVAC Description and Operation
Electrical Information Reference
- Circuit Testing
- Connector Repairs
- Testing for Intermittent Conditions and Poor Connections
- Wiring Repairs
Scan Tool Reference
Control Module References for scan tool information.
Circuit/System Verification
1. Ignition ON.
2. Verify the appropriate temperature sensor has a parameter displayed in HVAC
scan tool
information.
- If there is no scan tool parameter
Refer to Without Scan Tool Support.
- Go to next step: If there is a scan tool parameter
3. Refer to With Scan Tool Support
Circuit/System Testing
With Scan Tool Support
1. Ignition OFF and all vehicle systems OFF, disconnect the harness connector
at the appropriate
temperature sensor. It may take up to 10 min for all vehicle systems to power
down.
2. Test for less than 10 Ω between the low reference circuit terminal B and
ground.
- Ignition OFF, disconnect the harness connector at the K33 HVAC Control
Module.
- Test for less than 2 Ω in the low reference 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.
- Go to next step: If less than 10 Ω
3. Ignition ON.
4. Verify the appropriate scan tool temperature sensor parameter is less than
-37ºC (-35ºF).
- If greater than -37ºC (-35ºF).
- Ignition OFF, disconnect the harness connector at the K33 HVAC Control
Module.
- 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.
- Go to next step: If -37ºC (-35ºF) or less
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 110ºC
(230ºF).
- If less than 110ºC (230ºF)
- Ignition OFF, remove the jumper wire and disconnect the harness
connector at the K33
HVAC Control Module, ignition ON.
- 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.
- Go to next step: If less than 1 V
- Ignition OFF
- 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.
- Go to next step: If 110ºC (230ºF) or greater
7. Test or replace the temperature sensor.
Without Scan Tool Support
1. Ignition OFF and all vehicle systems OFF, disconnect the harness connector
at the appropriate
temperature sensor. It may take up to 10 min for all vehicle systems to power
down.
2. Test for less than 10 Ω between the low reference circuit terminal B and
ground.
- Ignition OFF, disconnect the harness connector at the K33 HVAC Control
Module.
- Test for less than 2 Ω in the low reference 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.
- Go to next step: If less than 10 Ω
3. Test for 4.8 - 5.2 V between the signal circuit terminal A and ground.
- Ignition OFF, disconnect the harness connector at the K33 HVAC Control
Module.
- Test for infinite resistance between the signal circuit and ground.
- If less than infinite resistance, repair the short to ground on the
circuit.
- Go to next step: If infinite resistance
- 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.
- Ignition OFF, disconnect the harness connector at the K33 HVAC Control
Module, ignition
ON.
- 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, replace the K33 HVAC Control Module.
- Go to next step: If between 4.8 - 5.2 V
4. Test or replace the temperature sensor.
5. Operate the vehicle within the Conditions for Running the DTC. You may also
operate the vehicle
within the conditions that you observed from the Freeze Frame/Failure Records
data.
6. Verify the DTC does not set.
Replace the K33 HVAC Control Module.
- Go to next step: If the DTC does not set
7. All OK
Repair Instructions
Perform the Diagnostic Repair Verification after completing the repair.
- HVAC Component Replacement Reference
- Control Module References for HVAC control module replacement,
programming and setup
READ NEXT:
Diagnostic Instructions
Perform the Diagnostic System Check - Vehicle prior to using this
diagnostic procedure.
Review Strategy Based Diagnosis for an overview of the diagnostic
approach.
Diag
Diagnostic Instructions
Perform the Diagnostic System Check - Vehicle prior to using this
diagnostic procedure.
Review Strategy Based Diagnosis for an overview of the diagnostic
approach.
Diag
Diagnostic Instructions
Perform the Diagnostic System Check - Vehicle prior to using this
diagnostic procedure.
Review Strategy Based Diagnosis for an overview of the diagnostic
approach.
Diag
SEE MORE:
Metric Wheel Nuts And Bolts Are Identified In The Following Way:
The Wheel Nut Has The Word Metric Stamped On The Face.
The Letter M Is Stamped On The End Of The Wheel Bolt.
The Thread Sizes Of Metric Wheel Nuts And The Bolts Are Indicated By The
Following Example: M12 X
1.5
M = Metric
12 =
Diagnostic Instructions
Perform the Diagnostic System Check - Vehicle prior to using this
diagnostic procedure.
Review Strategy Based Diagnosis for an overview of the diagnostic
approach.
Diagnostic Procedure Instructions provide an overview of each diagnostic
category.
DTC Descriptors
DT