DTC 169 Outside Temperature Sensor Voltage Low 2nd Design

The outside air temperature sensor is located behind the lower grille of the front fascia on the left side of the vehicle. In this position, it is exposed at airflow through the grill before the air enters the radiator. This provides a sample of the outside (ambient) air temperature.

The sensor is a thermistor used to control the signal voltage to the heater and A/C control. The heater and A/C control supplies a reference voltage (about 5 volts) on circuit PM 4 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. It also affects the mode and blower motor speed.

Resistance of the sensor varies from 169,400 ohms at -40°C (-40°F) to 1,245 ohms at 60°C (140°F). When the outside (ambient) 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 air temperature is hot, the thermistor resistance is low, the Heater and A/C control will receive a low signal voltage input.

The outside temperature is displayed on the display panel of the heater and A/C control. The displayed temperature value is derived from a series of calculations performed by a processor in the heater and A/C control. When the measured outside temperature is less than the displayed value, the processor filters less of the input signal, stores it in EEPROM, and rapidly updates the display. If the measured outside temperature is greater than the displayed value and the vehicle is moving, the processor filters more of the input signal, stores it in EEPROM, and updates the display at a much slower rate.

The number(s) below refer to the step number(s) on the diagnostic table.

2. This step checks for the available reference voltage from the heater and A/C control.

3. This step replaces the sensor. If the reference voltage was measured in the previous step, this would indicate the heater and A/C control and the wiring are OK.

7. This step checks for a possible intermittent problem. Moving the wiring during a diagnostic check may have corrected the problem temporarily. Review the suggestions in Diagnostic Aids when attempting to locate an intermittent problem.

9. This step replaces the heater and A/C control. If a DTC 169 continues to reset after a repair or no repair, the most likely cause is an internal malfunction in the heater and A/C control.