Buick Regal: DTC B018A, B048C, B048F, or B1395
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 B018A
Windshield Temperature Sensor Circuit
DTC B048C
Humidity Sensor Humidity Circuit
DTC B048F
Humidity Sensor Temperature Circuit
DTC B1395
Control Module Voltage Reference Output Circuit
For symptom byte information, refer to Symptom Byte List.
Diagnostic Fault Information
Circuit/System Description
The windshield temperature and inside moisture sensor includes the relative
humidity sensor, windshield
temperature sensor and humidity sensing element temperature sensor all in one
assembly.
This sensor assembly provides information about:
- Relative humidity level at the windshield inside the vehicle
- Temperature of the windshield inside the vehicle
- Temperature of the humidity sensor element
The relative humidity sensor measures the relative humidity of the
compartment side of the windshield.
It also detects the temperature of the windshield surface on the compartment
side. Both values are used
as control inputs for the HVAC control module application to calculate the fog
risk on windshield
compartment side and ability to reduce fuel consumption by decreasing A/C
compressor usage to a
minimum without causing any fog. The sensor will also enable partial
recirculation mode in order to
improve heat-up performance of the passenger compartment under cold ambient
temperature conditions
without the risk of mist build-up on the windshield. The humidity sensor element
temperature sensor
supplies the temperature of the humidity sensor element. It is only needed if
the thermal contact between
the humidity sensing element and the inside windshield surface is not
sufficient.
Conditions for Running the DTC
- Ignition ON.
- The HVAC control module is ON.
Conditions for Setting the DTC
B018A 02, B048C 02, or B048F 02
The HVAC control module detects the sensor signal out of range. The signal
voltage is less than 0.1 V
for more than 50 ms.
B018A 05, B048C 05, B048F 05 or B1395 07
The HVAC control module detects the sensor signal out of range. The signal
voltage is greater than 4.9
V for more than 50 ms.
B1395 03
The HVAC control module detects the 5 V reference voltage out of range. The 5
V reference voltage is
less than 4.5 V for more than 50 ms.
B1395 07
The HVAC control module detects the 5 V reference voltage out of range. The 5
V reference voltage is
greater than 5.5 V for more than 50 ms.
Action Taken When the DTC Sets
- The system will use the last valid values as default.
- If no value is read at the time of fault, the HVAC control module uses
60% for humidity.
Conditions for Clearing the DTC
The condition for setting the DTC is no longer present.
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 Testing
1. Ignition OFF and all vehicle systems OFF, disconnect the harness connector
at the B160
Windshield Temperature and Inside Moisture Sensor. It may take up to 10 min for
all vehicle
systems to power down.
NOTE: The scan tool must be disconnected from the vehicle before
performing the next test.
2. Test for less than 10 Ω between the low reference circuit terminal 3 and
ground.
- Ignition OFF, disconnect the harness connectors 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. Test for 4.8 - 5.2 V between the 5 V reference circuit terminal 1 and ground.
- Ignition OFF, disconnect the harness connectors at the K33 HVAC Control
Module.
- Test for infinite resistance between the 5 V reference 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 5 V 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.
- Ignition OFF, disconnect the harness connectors at the K33 HVAC Control
Module, ignition
ON.
- Test for less than 1 V between the 5 V reference 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
5. Verify the scan tool parameters listed below are less than -37ºC
(-35ºF).
- Windshield Temperature
- Passenger Compartment Humidity Sensor Temperature
- If -37ºC (-35ºF) or greater
- Ignition OFF, disconnect the harness connectors at the K33 HVAC Control
Module.
- Test for infinite resistance between the signal circuit terminals listed
below and ground:
- Windshield temperature sensor signal terminal 4
- Passenger compartment humidity sensor temperature signal terminal 5
- 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 less than -37ºC (-35ºF)
6. Test for 4.8 - 5.2 V between the signal circuit terminals listed below and
ground.
- Windshield temperature sensor signal terminal 4
- Passenger compartment humidity sensor temperature signal terminal 5
- If less than 4.8 V
- 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.
- If greater than for 5.2 V
- 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
7. Install a 3 A fused jumper wire between the low reference circuit terminal
3 and each signal
circuit terminal listed below:
- Windshield temperature sensor signal terminal 4
- Passenger compartment humidity sensor temperature signal terminal 5
8. Verify the appropriate scan tool parameter listed below is greater than
114ºC (238ºF).
- Windshield Temperature
- Passenger Compartment Humidity Sensor Temperature
- If 114ºC (238ºF) or less
- Ignition OFF, remove the jumper wire and disconnect the harness
connectors at the K33
HVAC Control Module, ignition ON.
- Test for less than 1 V between the signal circuit terminals listed below
and ground:
- Windshield temperature sensor signal terminal 4
- Passenger compartment humidity sensor temperature signal terminal 5
- If 1 V or greater, repair the short to voltage on the circuit.
- Go to next step: If less than 1 V
- 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 greater than 114ºC (238ºF)
9. Remove the jumper wire.
10. Verify the scan tool Passenger Compartment Humidity parameter is greater
than 95%.
- Ignition OFF, disconnect the harness connectors at the K33 HVAC Control
Module, ignition
ON.
- Test for infinite resistance between the signal circuit terminal 2 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 greater than 95%
11. Test for 4.8 - 5.2 V between the signal circuit terminal 2 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.
- If greater than for 5.2 V
- 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
12. Install a 3 A fused jumper wire between the passenger compartment
humidity signal circuit
terminal 2 and the low reference circuit terminal 3.
13. Verify the scan tool Passenger Compartment Humidity Sensor parameter is less
than 5%.
- Ignition OFF, remove the jumper wire and disconnect the harness
connectors at the K33
HVAC Control Module, ignition ON.
- Test for less than 1 V between the signal circuit terminal 2 and ground.
- If 1 V or greater, repair the short to voltage on the circuit.
- Go to next step: If less than 1 V
- 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 less than 5%
14. Test or replace the B160 Windshield Temperature and Inside Moisture
Sensor
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
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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
D