Climate Control - EMTC

Diagnostic Routine Q

Diagnostic Overview

B1A61:11, B1A61:15

Refer to Wiring Diagram Set 54 for schematic and connector information Electrical Diagrams.

Normal Operation and Fault Conditions

The in-vehicle temperature and humidity sensors receive a ground from the HVAC (Heating, Ventilation, and Air Conditioning) module. The sensor varies its resistance with the temperature. As the temperature rises, the resistance falls. As the temperature falls, the resistance rises. The HVAC (Heating, Ventilation, and Air Conditioning) module measures this resistance to determine the temperature at the sensor. The sensor DTCs (Diagnostic Trouble Codes) set if there is a fault in either the temperature or humidity part of the sensor or circuits.

DTC Fault Trigger Conditions






Pinpoint Test

1. CHECK THE IN-VEHICLE TEMPERATURE AND HUMIDITY SENSOR RESISTANCE

1. Ignition OFF.

2. Disconnect: In-Vehicle Temperature and Humidity Sensor.

3. Carry out the in-vehicle temperature and humidity sensor component test, REFER to In-Vehicle Temperature Sensor In-Vehicle Temperature Sensor.

Does the in-vehicle temperature and humidity sensor test OK?








2. CHECK THE HVAC (Heating, Ventilation, and Air Conditioning) MODULE OUTPUT VOLTAGE

1. Ignition ON.

2. Measure:





Is the voltage between 4.7 and 5.1 volts?








3. CHECK THE IN-VEHICLE TEMPERATURE AND HUMIDITY SENSOR FEEDBACK CIRCUIT FOR AN OPEN

1. Ignition OFF.

2. Disconnect: HVAC (Heating, Ventilation, and Air Conditioning) Module C228A.

3. Disconnect: HVAC (Heating, Ventilation, and Air Conditioning) Module C228B.

4. Measure:





Is the resistance less than 3 ohms?








4. CHECK THE SIGNAL RETURN CIRCUIT FOR AN OPEN

1. Measure:





Is the resistance less than 3 ohms?








5. CHECK THE SIGNAL RETURN CIRCUIT FOR A SHORT TO VOLTAGE

1. Ignition ON

2. Measure:





Is any voltage present?








6. CHECK THE IN-VEHICLE TEMPERATURE AND HUMIDITY SENSOR FEEDBACK CIRCUIT FOR A SHORT TO THE SIGNAL RETURN CIRCUIT

1. Ignition OFF.

2. Disconnect: HVAC (Heating, Ventilation, and Air Conditioning) Module C228A.

3. Disconnect: HVAC (Heating, Ventilation, and Air Conditioning) Module C228B.

4. Measure:





Is the resistance greater than 10,000 ohms?








7. CHECK THE IN-VEHICLE TEMPERATURE AND HUMIDITY SENSOR FEEDBACK CIRCUIT FOR A SHORT TO GROUND

1. Measure:





Is the resistance greater than 10,000 ohms?








8. CHECK FOR CORRECT HVAC (Heating, Ventilation, and Air Conditioning) MODULE OPERATION

1. Ignition OFF.

2. Disconnect and inspect all HVAC (Heating, Ventilation, and Air Conditioning) module connectors.

3. Repair:

- corrosion (install new connector or terminals- clean module pins)
- damaged or bent pins- install new terminals/pins
- pushed-out pins- install new pins as necessary

4. Reconnect the HVAC (Heating, Ventilation, and Air Conditioning) module connectors. Make sure they seat and latch correctly.

5. Reconnect the In-Vehicle Temperature and Humidity Sensor connector. Make sure it seats and latches correctly.

6. Operate the system and determine if the concern is still present.

Is the concern still present?