SL L4-1.9L SOHC VIN 9 (1991)
Intake Air Temperature Sensor: Description and Operation
Air Temperature Sensor. (SOHC Engines)
Air Temperature Sensor (ATS) Wiring.
DESCRIPTION
The air temperature sensor is a thermistor-type sensor mounted in the engine inlet air system. A thermistor resists the flow of electricity similar to a
resistor. However, the resistance of a thermistor increases as the temperature drops. For example, at a low air temperature a thermistor produces a
high resistance of 93,000 ohms at -40°C (-40°F), while a high temperature causes low resistance of 65 ohms at 140°C (248°F).
The air temperature sensor is a two-wire sensor that receives a reference signal voltage from the PCM to sensor pin B and a sensor reference
ground from the PCM to sensor pin A.
The PCM supplies the 5 volt reference signal to the air temperature sensor through a current limiting resistor located inside the PCM. This signal
is received by the PCM and indicates the temperature of the air entering the engine. This sensor input is used by the PCM for fuel enrichment,
ignition timing, EGR operation, canister purge control, idle speed control, and Closed Loop fuel control.
