Intake air sensor (688), T8: Connection

Fig 1: Identifying Intake Air Sensor (688), T8 Functional Diagram

Courtesy of SAAB-SCANIA OF AMERICA, INC.

Fig 2: Identifying Intake Air Sensor (688), T8 Circuit Diagram

Courtesy of SAAB-SCANIA OF AMERICA, INC.

Sensor capacitance between the metal plating of the discs is changed based on the pressure. A circuit integrated in the sensor converts the capacitance to an analogue voltage.

Based on the pressure in the charge air pipe, the pressure sensor yields a proportional voltage to control module pin 24(B).

The control module measures air temperature in the induction pipe by supplying the sensor 5 V through a 1.50 kOhm resistor integrated in the control module from pin 10(B). Voltage across the resistor in the control module is proportional to the intake air temperature.

Airmass control determines which airmass/combustion is to be sucked in during the cylinder's intake stroke. The value corresponds to engine torque.

Throttle control sets the throttle so that the actual airmass/combustion matches that which is requested. If air density before the throttle is high, a smaller throttle angle is required than if the air density is low. Air density is therefore calculated by the control module using boost pressure and intake air temperature.

At normal atmospheric pressure, 100 kPa, voltage from the sensor is approx. 2.1 V.