Sensor Circuit
DTC B018A, B048C, B048F, or B1395
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 B018A 02
- Windshield Temperature Sensor Circuit Short to Ground
DTC B018A 05
- Windshield Temperature Sensor Circuit High Voltage/Open
DTC B048C 02
- Humidity Sensor Humidity Circuit Short to Ground
DTC B048C 05
- Humidity Sensor Humidity Circuit High Voltage/Open
DTC B048F 02
- Humidity Sensor Temperature Circuit Short to Ground
DTC B048F 05
- Humidity Sensor Temperature Circuit High Voltage/Open
DTC B1395 03
- Control Module Voltage Reference Output Circuit Low Voltage
DTC B1395 07
- Control Module Voltage Reference Output Circuit High Voltage
Diagnostic Fault Information
Circuit/System Description
The windshield temperature and inside moisture sensor integrates the relative humidity sensor, windshield temperature sensor and humidity sensing element temperature sensor.
This sensor assembly provides information about:
* Relative humidity level on inside windshield
* Temperature of the inside windshield
* Temperature of the humidity sensor element
The relative humidity sensor measures the relative humidity on 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 power 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, B048C 02 or B1395 03
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, B048C 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.
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 HVAC - Automatic
Connector End View Reference
Component Connector End Views Sunshade - Left Front
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 Programming and Relearning for scan tool information
Circuit/System Testing
DTC B1395
1. Ignition OFF, disconnect the harness connector at the components listed below:
* B160 windshield temperature and inside moisture sensor
* M37 mode door actuator
* M46 air recirculation door actuator
* M6 air temperature door actuator
2. Disconnect the X3 harness connector at the K33 HVAC control module, ignition ON.
3. Test for less than 1 V between the K33 HVAC control module 5 V reference circuit terminals listed below and ground:
* Terminal 10 X3
* Terminal 20 X3
• If 1 V or greater
Repair the short to voltage on the circuit.
• If less than 1 V
4. Ignition OFF.
5. Test for infinite resistance between the K33 HVAC control module 5 V reference circuit terminals listed below and ground:
* Terminal 10 X3
* Terminal 20 X3
• If less than infinite resistance
Repair the short to ground on the circuit.
• If infinite resistance
6. Clear all DTCs, connect the X3 harness connector at the K33 HVAC control module, ignition ON.
7. Verify DTC B1395 is not set.
• If the DTC is set.
Replace the K33 HVAC control module.
• If the DTC is not set.
8. Verify DTC B1395 does not set after connecting each of the components listed below, one at a time:
* B160 windshield temperature and inside moisture sensor
* M37 mode door actuator
* M46 air recirculation door actuator
* M6 air temperature door actuator
• If the DTC sets after connecting one of the components
Replace the component that was connected immediately before the DTC set.
• If the DTC does not set
9. All OK.
DTC B018A, B048C, or B048F
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 2 minutes for all vehicle systems to power down.
2. Test for less than 60 ohms between the low reference circuit terminal 3 and ground.
• If 60 ohms or greater
1. Ignition OFF, disconnect the harness connector at the K33 HVAC control module.
2. 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 60 ohms
3. Ignition ON.
4. Test for 4.8-5.2 V between the 5 V reference circuit terminal 1 and ground.
• If less than 4.8 V
1. Ignition OFF, disconnect the harness connector at the K33 HVAC control module.
2. 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
3. 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
1. Ignition OFF, disconnect the harness connector at the K33 HVAC control module, Ignition ON.
2. 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
5. Verify the scan tool parameters listed below are less than -37°C (-35°F).
* Windshield Temperature
* Passenger Compartment Humidity Sensor Temperature
• If -37°C (-35°F) or greater
1. Ignition OFF, disconnect the harness connector at the K33 HVAC control module.
2. 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 -37°C (-35°F)
6. Verify the scan tool Passenger Compartment Humidity parameter is greater than 95%.
• If 95% 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 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%
7. Install a 3 A fused jumper wire between each signal circuit terminal listed below and the low reference circuit terminal 3 one at a time.
* 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 114°C (238°F).
* Windshield Temperature
* Passenger Compartment Humidity Sensor Temperature
• If 114°C (238°F) or less
1. Ignition OFF, disconnect the harness connector at the K33 HVAC control module.
2. 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
3. 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 114°C (238°F)
9. Install a 3 A fused jumper wire between the passenger compartment humidity sensor signal circuit terminal 2 and the low reference circuit terminal 3.
10. Verify the scan tool Passenger Compartment Humidity parameter is less than 5%.
• If 5% or greater
1. Ignition OFF, disconnect the harness connector at the K33 HVAC control module.
2. 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%
11. Ignition OFF, disconnect the harness connector at the K33 HVAC control module, Ignition ON.
12. 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
13. Test or replace the B160 windshield temperature and inside moisture sensor.
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the repair.
* HVAC Component Replacement Reference HVAC Component Replacement Reference
* Control Module References Programming and Relearning for HVAC control module replacement, programming and setup