Intake air temperature sensor: Notes

WARNING: This page is about a different car, the 2001 Saab 9-3. However, it is still accessible from the selected car via links, so may be relevant.

Fig 1: Identifying Intake Air Temperature Sensor - Control Module Communication Diagram

Courtesy of SAAB-SCANIA OF AMERICA, INC.

Fig 2: Identifying Intake Air Temperature Sensor - Control Module Communication Circuit Diagram

Courtesy of SAAB-SCANIA OF AMERICA, INC.

The temperature sensor is located in the intake manifold and is NTC type. The control module measures the air temperature in the intake manifold by supplying the sensor with 5V from pin 15 through a 2.74 K/ohm resistor integrated in the control module. The sensor is grounded from pin 70. The voltage across the resistor in the control module is proportional to the intake air temperature.

The temperature is used to:

Determine the density of the charge air together with charge air pressure. The charge air density is used by the air mass control to correct the throttle angle.
Correct the PWM ratio of the charge air control valve. A higher PWM ratio is required at high temperatures to obtain the same air mass/combustion.
Correct the ignition timing. A more advanced ignition is required at low temperatures.
Blocking certain diagnoses:
- Blocking certain diagnoses at temperatures lower than -7°C.
- Reactivate certain diagnoses at temperatures higher than 5 °C.