Chevrolet Trax: DTC B018A, B048C, B048F, OR B1395: Windshield temperature sensor/humidity
sensor/control module voltage reference
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
![Diagnostic Fault Information](images/manuals/4484/index415(10).jpg)
![Diagnostic Fault Information](images/manuals/4484/index416(10).jpg)
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 Schematics (Encore)
Connector End View Reference
WIRING SYSTEMS AND POWER MANAGEMENT - COMPONENT CONNECTOR END VIEWS -
INDEX - ENCORE WIRING SYSTEMS AND POWER MANAGEMENT - COMPONENT
CONNECTOR END VIEWS - INDEX - TRAX
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
- 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.
- Test for less than 10 ohms between the low reference circuit terminal 3
and ground.
If 10 ohms or greater
- Ignition OFF, disconnect the harness connectors at the K33 HVAC Control
Module.
- Test for less than 2 ohms in the low reference circuit end to end.
- If 2 ohms or greater, repair the open/high resistance in the circuit.
- If less than 2 ohms, replace the K33 HVAC Control Module.
If less than 10 ohms
- Ignition ON.
- Test for 4.8-5.2 V between the 5 V reference circuit terminal 1 and
ground.
If less than 4.8 V
- 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.
- If infinite resistance
- Test for less than 2 ohms in the 5 V reference circuit end to end.
- If 2 ohms or greater, repair the open/high resistance in the circuit.
- If less than 2 ohms, replace the K33 HVAC Control Module.
If greater than 5.2 V
- 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.
If between 4.8-5.2 V
- 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.
If less than -37ºC (-35ºF)
- 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
- 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.
- If less than 1 V
- Test for less than 2 ohms in the signal circuit end to end.
- If 2 ohms or greater, repair the open/high resistance in the circuit.
- If less than 2 ohms, replace the K33 HVAC Control Module.
If greater than 114ºC (238ºF)
- Remove the jumper wire.
- Verify the scan tool Passenger Compartment Humidity parameter is greater
than 95%.
If 95% or less
- 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.
If greater than 95%
- Install a 3 A fused jumper wire between the passenger compartment
humidity signal circuit terminal 2
and the low reference circuit terminal 3.
- Verify the scan tool Passenger Compartment Humidity Sensor parameter is
less than 5%.
If 5% or greater
- 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.
- If less than 1 V
- Test for less than 2 ohms in the signal circuit end to end.
- If 2 ohms or greater, repair the open/high resistance in the circuit.
- If less than 2 ohms, replace the K33 HVAC Control Module.
If less than 5%
- 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
SEE MORE:
Visual Aiming Preparation Procedure
NOTE: Some state and
local laws specify requirements for headlamp aim. Comply with
all of these laws when performing any headlamp aiming operations.
Headlamp aim should be checked:
When a new headlamp capsule is installed.
If service or repairs to the front en
Removal Procedure
WARNING: Refer to Approved Equipment for Collision Repair Warning .
NOTE: The roof front header panel is made of Ultra High Strength
Steel and
should be replaced only at factory joints. Repairing or sectioning of this
part is not recommended. Refer to Ultra High Strength Steel.