For 1990-2009 cars

### 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 Descriptor

DTC B018A 02: Windshield Temperature Sensor Circuit Short to Ground
DTC B018A 05: Windshield Temperature Sensor Circuit Short to Battery or Open
DTC B048C 02: Humidity Sensor Humidity Circuit Short to Ground
DTC B048C 05: Humidity Sensor Humidity Circuit Short to Battery or Open
DTC B048F 02: Humidity Sensor Temperature Circuit Short to Ground
DTC B048F 05: Humidity Sensor Temperature Circuit Short to Battery or Open
DTC B1395 03: Control Module Voltage Reference Output Circuit Voltage Below Threshold
DTC B1395 07: Control Module Voltage Reference Output Circuit Voltage Above Threshold

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
Windshield Temperature and Inside Moisture Sensor 5 V Reference | B1395 03 | B1395 03 | B1395 07 | --
Humidity Signal | B048C 02 | B048C 05 | B048C 05 | --
Humidity Temperature Signal | B048F 02 | B048F 05 | B048F 05 | --
Windshield Temperature Signal | B018A 02 | B018A 05 | B018A 05 | --
Windshield Temperature and Inside Moisture Sensor Ground | -- | B018A 05, B048C 05, B048F 05, B1395 03 | -- | --

### 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

#### Connector End View Reference

Component Connector End Views

#### 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. Verify that DTC B1395 03 or B1395 07 is not present.

⇒ | If DTC is present, refer to Windshield Temperature And Inside Moisture Sensor Power Supply Malfunction.

2. Verify that DTC B048C 02 or B048C 05 is not present.

⇒ | If DTC is present, refer to Humidity Sensor Humidity Circuit Malfunction.

3. Verify that DTC B048F 02 or B048F 05 is not present.

⇒ | If DTC is present, refer to Humidity Sensor Temperature Circuit Malfunction.

4. Verify that DTC B018A 02 or B018A 05 is not present.

⇒ | If DTC is present, refer to Windshield Temperature Sensor Circuit Malfunction.

5. Measure actual temperature using a thermometer at the windshield temperature and inside moisture sensor. Compare this value to the scan tool Passenger Compartment Humidity Sensor Temperature parameter. The measured temperature should be within 5°C (9°F) difference of parameter value.

⇒ | If not within the specified range, replace the B160 Windshield Temperature and Inside Moisture Sensor.

6. Measure actual temperature using a thermometer at the windshield temperature and inside moisture sensor. Compare this value to the scan tool Windshield Temperature parameter. The measured temperature should be within 5°C (9°F) difference of parameter value.

⇒ | If not within the specified range, replace the B160 Windshield Temperature and Inside Moisture Sensor.

### Circuit/System Testing

#### Windshield Temperature and Inside Moisture Sensor Power Supply Malfunction

1. Ignition OFF, disconnect the harness connector at the B160 Windshield Temperature and Inside Moisture Sensor.
2. Test for less than 5 Ω between the ground circuit terminal 3 and ground.

⇒ | If greater than the specified range, test the ground circuit for an open/high resistance.

3. Ignition ON, test for 4.8-5.2 V between the ground circuit terminal 3 and the reference voltage circuit terminal 1.

⇒ | If less than the specified range, test the signal circuit for a short to ground or open/high resistance. If the circuit tests normal, replace the K33 HVAC Control Module.

⇒ | If greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the K33 HVAC Control Module.

4. If all circuits test normal, replace the B160 Windshield Temperature and Inside Moisture Sensor.

#### Humidity Sensor Humidity Circuit Malfunction

1. Ignition OFF, disconnect the harness connector at the B160 Windshield Temperature and Inside Moisture Sensor.
2. Ignition ON, test for 4.8-5.2 V between the signal circuit terminal 2 and ground.

⇒ | If less than the specified range, test the signal circuit terminal for a short to ground or open/high resistance. If the circuit tests normal, replace the K33 HVAC Control Module.

⇒ | If greater than the specified range, test the signal circuit terminal for a short to battery. If the circuit tests normal, replace the K33 HVAC Control Module.

3. If all circuits test normal, replace the B160 Windshield Temperature and Inside Moisture Sensor and verify the DTC does not reset.

⇒ | If the DTC resets, replace the K33 HVAC Control Module.

#### Humidity Sensor Temperature Circuit Malfunction

1. Ignition OFF, disconnect the harness connector at the B160 Windshield Temperature and Inside Moisture Sensor.
2. Ignition ON, test for 4.8-5.2 V between the signal circuit terminal 5 and ground.

⇒ | If less than the specified range, test the signal circuit terminal for a short to ground or open/high resistance. If the circuit tests normal, replace the K33 HVAC Control Module.

⇒ | If greater than the specified range, test the signal circuit terminal for a short to battery. If the circuit tests normal, replace the K33 HVAC Control Module.

3. If all circuits test normal, replace the B160 Windshield Temperature and Inside Moisture Sensor and verify the DTC does not reset.

⇒ | If the DTC resets, replace the K33 HVAC Control Module.

#### Windshield Temperature Sensor Circuit Malfunction

1. Ignition OFF, disconnect the harness connector at the B160 Windshield Temperature and Inside Moisture Sensor.
2. Ignition ON, test for 4.8-5.2 V between the signal circuit terminal 4 and ground.

⇒ | If less than the specified range, test the signal circuit terminal for a short to ground or open/high resistance. If the circuit tests normal, replace the K33 HVAC Control Module.

⇒ | If greater than the specified range, test the signal circuit terminal for a short to battery. If the circuit tests normal, replace the K33 HVAC Control Module.

3. If all circuits test normal, replace the B160 Windshield Temperature and Inside Moisture Sensor and verify the DTC does not reset.

⇒ | If the DTC resets, replace the K33 HVAC Control Module.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Inside Air Moisture and Windshield Temperature Sensor Replacement

• | Control Module References for HVAC control module replacement, setup, and programming