900 Turbo Convertible L4-1985cc 2.0L DOHC Turbo EFI (1994)
Transmission Speed Sensor: Description and Operation
Input Shaft Speed Sensor
INPUT SHAFT SPEED SENSOR
The Input Shaft Speed (ISS) sensor is fitted in the transmission housing. It gives the Transmission Control Module (TCM) information about the
incoming rpm to the transmission.
The ISS sensor is of the electro-magnetic (inductive) type and measures the incoming rpm after the torque converter (the turbine rpm) by being
affected by a toothed pulse wheel (a drum on the C1 clutch). The sensor's signal voltage, a sine voltage, increases with the engine speed. When
idling it is 1.2 - 1.4 V and at 2500 rpm it is 2.2 V, measured between pins 2 and 1 on the sensor.
Pin 12 is signal voltage and pin 31 is signal ground. The resistance between pins 2 and 1 on the sensor connector is 300 - 600 ohms.
The TCM uses the ISS rpm signal and the speed of the car to calculate gear shifting times. The information about rpm and speed affects the
regulation of fluid pressure, control of the lock-up function and the reduction in torque, which results in smooth shifting of gears.
