Transmission Input Speed Sensor (Speed Of The Input Shaft)
The transmission input speed sensor, (input shaft speed) is positioned in the transmission housing. The sensor is an active sensor and is supplied with 12 V. When the driven gearwheel rotates, the sensor generates a pulsed current (quadratic wave) where the strength of the current depends on the position of the pulse wheel. The signals from the coil in the sensor are then effected by a magnetic resistance element, which generates a current which oscillates between 7 mA and 14 mA, and the frequency of which increase with speed. The transmission control module (TCM) calculates the transmission input speed using the signal from the sensor.
The input speed is compared with the transmission output speed from the transmission speed sensor signal to calculate the gear ratio.
There are diagnostics for the transmission input speed sensor.