Transmission output speed sensor (speed of the output 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 Output Speed Sensor (Speed Of Output Shaft)

Courtesy of VOLVO CARS OF NORTH AMERICA.

The transmission output shaft speed sensor is positioned on the transmission housing. The sensor is electro-magnetic and acts on a toothed pulse wheel. The sensor provides signals to the transmission control module (TCM) about the vehicle speed. The transmission speed sensor is an active sensor and is supplied with 12 V. When the pulse wheel 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 control module calculates the transmission output speed using the signals from the sensor. The signal is compared with the signal from the transmission input speed sensor and is used to calculate the gear ratio as well as for diagnostics.

There are diagnostics for the transmission output speed sensor.