For 1990-2009 cars

## DTC 10 Inside Air Temperature Sensor Voltage Low Early Software Version

### Circuit Description

The inside air temperature sensor is located in the heater and A/C control behind a small grill. In this position, it is exposed to the air that is present in the passenger compartment. This provides a sample of the inside air temperature.

The sensor is a thermistor used to control the signal voltage at the heater and A/C control. The heater and A/C control supplies a reference voltage (about 5 volts internally) to the sensor and measures the voltage drop in the circuit to obtain a temperature signal. This signal is an input that tells the heater and A/C control how much cooling or heating will be required to deliver to the passenger compartment. After an initial start-up, the heater and A/C control uses the temperature input from the inside air temperature sensor for automatic control. Eventually the temperature input from both air outlet temperature sensor's overrides the input from the inside air temperature sensor and becomes the primary temperature input to the heater and A/C control.

When the inside air temperature is cold, the thermistor resistance is high; therefore, the heater and A/C control will receive a high signal voltage input. If the inside air temperature is hot, the thermistor resistance is low, the heater and A/C control will receive a low signal voltage input.

### Conditions for Setting the DTC

• | The sensors circuit is checked continuously every 200 ms. with the ignition in the ON position.

• | Circuit stays at or near zero voltage.

### Action Taken When the DTC Sets

• | The heater and A/C control stores a DTC 10 in memory.

• | The system will use 24°C (75°F) as a default value.

### Conditions for Clearing the DTC

• | The conditions for the fault are no longer present.

• | Using a scan tool.

• | A history DTC will clear after 20 consecutive ignition cycles if the conditions for the fault is no longer present.

### Test Description

The numbers below refer to the step numbers on the diagnostic table.

1. Because the inside air temperature sensor resides in the heater and A/C control and is not serviceable, the only procedure is to replace the entire assembly.

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Was the Air Delivery System Check performed? | -- | Go to Step 2 | Go to Air Delivery System Check
2 | Replace the heater and A/C control. Refer to Heater and A/C Control Replacement for the procedure. Is the replacement complete? | -- | Go to Air Delivery System Check | --

## DTC 10 Inside Air Temperature Sensor Voltage Low Latest Software Version

### Test Description

The numbers below refer to the step numbers on the diagnostic table.

1. Determines if the malfunction is present.

2. Moving the component might cause the malfunction to appear.

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Was the Air Delivery System Check performed? | -- | Go to Step 2 | Go to HVAC Air Delivery System Check
2 |

1. Install the scan tool.
2. Select INSIDE AIR TEMP SENSOR and display the voltage.

Does the scan tool display the specified voltage?

Less than 0.2 V

Go to Step 4

Go to Step 3

3 |

1. Remove the heater and A/C control from the mounting bracket.
2. Move the controller into different positions while monitoring the scan tool.

Does the sensor value change?

--

Go to Step 4

Go to Diagnostic Aids

4 | Replace and program the heater and A/C control. Refer to Control Assembly Replacement for the programming procedures. Is the replacement and programming complete? | -- | Go to HVAC Air Delivery System Check | --