Intake Air Temperature (IAT) Sensor (for 3.8L engine) (Chevrolet Lumina 1)

Contents: General description ↧ Examination ↧

General description

95. The intake air temperature sensor is located inside the air intake directly behind the air filter housing. This sensor works like a resistor, the resistance of which changes along with fluctuations in the temperature of the air entering the engine. At low air temperatures the resistance will be high (for example, at -5°C the sensor resistance is 100,000 Ohm; as the temperature increases, the resistance drops (for example, at 131°C the resistance will drop to 70 ohms). The PCM unit supplies a signal voltage of approximately 5 V to the IAT sensor. This voltage changes in accordance with the temperature of the air entering the engine. If the air is cold, the signal voltage will be high, and vice versa, when the air temperature is high, the voltage will drop.

Examination

96. To check the serviceability of the IAT sensor, disconnect the two-pin electrical connector from it and turn on the ignition, but do not start the engine.

97. Measure the voltage (signal) on contact "A" (see illustration). The voltmeter should show a value close to 5 V.

4.97. Measure the signal voltage on the sensor by touching the voltmeter lead to its contact "A" (orange wire)

98. If the signal voltage differs from the specified value, take the PCM to a repair shop.

99. Measure the resistance at the sensor contacts (see illustration). If the air temperature is low, the sensor resistance should be high. Then start the engine and let it idle (in a cold state). After waiting for it to warm up to normal operating temperature, turn off the ignition, disconnect the IAT sensor and measure the voltage at its contacts. When the air temperature is high, the resistance of the sensor should be small. If the sensor resistance has a different temperature dependence, replace the sensor with a new one.