Transmission input speed sensor (speed of the input shaft)

WARNING: This page does not describe the selected car, but rather 8 other vehicles, including the 2006 Volvo S80, 2005 Volvo S80, 2004 Volvo S80, 2003 Volvo S80, and 2002 Volvo S80. However, it is still accessible from the selected car via links, so may be relevant.

Fig 1: Transmission Input Speed Sensor (Speed Of Input Shaft)

Courtesy of VOLVO CARS OF NORTH AMERICA.

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.