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. |
Diagnostic Aids
| • | If the DTC is a history or an intermittent. Remove the component and try to perform the tests shown while "wiggling" wiring and connectors, this can often cause the malfunction to appear. |
| • | Visually inspect sensor for damage, corrosion or water intrusion. |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
Determines if the malfunction is present.
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Moving the component might cause the malfunction to appear.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Was the Air Delivery System Check performed? | -- | ||
Does the scan tool display the specified voltage? | Less than 0.2 V | |||
Does the sensor value change? | -- | 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? | -- | -- |
