Volt

DTC B018A, B048C, B048F, or B1395

The windscreen temperature and inside moisture sensor integrates the relative humidity sensor, windscreen temperature sensor and humidity sensing element temperature sensor.

This sensor assembly provides information about:

The relative humidity sensor measures the relative humidity on the compartment side of the windscreen. It also detects the temperature of the windscreen surface on the compartment side. Both values are used as control inputs for the HVAC control module application to calculate the fog risk on windscreen 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 windscreen. 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 windscreen surface is not sufficient.

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.

The condition for setting the DTC is no longer present.

Schematic Reference

HVAC Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Automatic HVAC Description and Operation

Electrical Information Reference

Scan Tool Reference

Control Module References for scan tool information

1. Vehicle OFF and all vehicle systems OFF, disconnect the harness connector at the B160 windscreen temperature and inside moisture sensor. It may take up to 2 minutes for all vehicle systems to power down.
2. Test for less than 10 Ω between the low reference circuit terminal 3 and ground.

⇒	If 10 Ω or greater

2.1.	Vehicle OFF, disconnect the harness connector at the K33 HVAC control module.

2.2.	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.

⇓	If less than 10 Ω

3. Vehicle in Service Mode.
4. Test for 4.8-5.2 V between the 5 V reference circuit terminal 1 and ground.

⇒	If less than 4.8 V

4.1.	Vehicle OFF, disconnect the harness connector at the K33 HVAC control module.

4.2.	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

4.3.	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.

⇒	If greater than 5.2 V

4.1.	Vehicle OFF, disconnect the harness connector at the K33 HVAC control module, vehicle in Service Mode.

4.2.	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 Windscreen Temperature and Passenger Compartment Humidity Sensor Temperature parameters are less than -39°F.

⇒	If -39°F or greater

5.1.	Vehicle OFF, disconnect the harness connector at the K33 HVAC control module, vehicle in Service Mode.

5.2.	Test for less than 1 V between the signal circuit terminals listed below and ground.

-	Windscreen 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, replace the K33 HVAC control module.

⇓	If less than -39°F

6. Verify the scan tool Passenger Compartment Humidity parameters is greater than 95%.

⇒	If 95% or less

6.1.	Vehicle OFF, disconnect the harness connector at the K33 HVAC control module, vehicle in Service Mode.

6.2.	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, replace the K33 HVAC control module.

⇓	If greater than 95%

7. Install a 3 A fused jumper wire between the signal circuit terminals listed below and the 5 V reference circuit terminal 1.

•	Windscreen temperature sensor signal terminal 4

•	Passenger compartment humidity sensor temperature signal terminal 5

8. Verify the scan tool Windscreen Temperature and Passenger Compartment Humidity Sensor Temperature parameters are greater than 239°F.

⇒	If 239°F or less

8.1.	Vehicle OFF, disconnect the harness connector at the K33 HVAC control module.

8.2.	Test for infinite resistance between the signal circuit terminals listed below and ground.

-	Windscreen 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

8.3.	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 239°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 Sensor parameter is less than 5%.

⇒	If 5% or greater

10.1.

Vehicle OFF, disconnect the harness connector at the K33 HVAC control module.

10.2.

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 less than 5%

11. Test or replace the B160 windscreen temperature and inside moisture sensor.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.