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DTC B018A, B048C, B048F, or B1395

DTC B018A, B048C, B048F, or B1395

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 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 Short to Ground Open/High Resistance Short to Voltage Signal Performance
Windshield Temperature and Inside Moisture Sensor 5V Reference

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,

-

-



Circuit/System Description

The windshield temperature and inside moisture sensor includes the relative humidity sensor, windshield temperature sensor and humidity sensing element temperature sensor.

This sensor assembly provides information about:


• Relative humidity level at windshield inside

• Temperature of the windshield inside

• 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 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

Circuit/System Verification


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

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

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

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

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

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

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

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

9. 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.

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

11. 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.

12. 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.

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

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

5. 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.

6. 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.

7. 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 Ω between the ground circuit terminal 3 and ground.

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

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

5. 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.

6. Test for 4.8-5.2 V between the signal circuit terminal 2 and ground.

7. 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.

8. 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.

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

10. 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.

3. 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.

4. 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 and verify the DTC does not reset.

6. 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.

3. 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.

4. 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 and verify the DTC does not reset.

6. 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