Intake air temperature sensor

Intake air temperature sensor

Intake air temperature is measured by temperature sensor (B) located on the butterfly valve case.

This sensor consists of a plastic case on which is located the reactive element (1), which consists of a resistance (N.T.C.) that varies in inverse proportion to temperature.

If temperature is between 15° C - 30° C, resistance is 3.3 - 1.5 kΩ. If temperature is about 80° C, the resistance is 0.280 - 0.360 Ω.

Terminal 13 of the ECU (A) supplies terminal 1 of sensor (B); the circuit is earthed from terminal 2 of the sensor to terminal 27 of the ECU.

When the sensor is disconnected, the ECU supplies a voltage of 5 V. With the sensor connected, the supply voltage alters according to temperature (internal sensor resistance).

Recovery

When the air temperature sensor is short-circuited (d.c.) or circuitis open (a.c.), the ECU receives implausible signals, i.e.:

• d.c. sensor: air temperature > 128° C
• a.c. sensor: air temperature < -50° C

In these cases, the ECU implements a Recovery strategy which takes an air temperature of 20° C as a reference.