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B048C




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 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/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 (Connector End Views By Name)
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 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 ohm 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 reference voltage 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 reference voltage 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. Test for less than 5 ohm 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 reference voltage circuit for an open/high resistance. If the circuit tests normal, replace the K33 HVAC Control Module.

4. 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.

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

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.

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.

Repair Instructions

Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.

* Inside Air Moisture and Windshield Temperature Sensor Replacement (Inside Air Moisture and Windshield Temperature Sensor Replacement)
* Control Module References (Programming and Relearning) for HVAC control module replacement, setup, and programming

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