Circuit/System Description

WARNING: This page is about a different car, the 2008 GMC Sierra and 2008 Chevrolet Silverado. However, it is still accessible from the selected car via links, so may be relevant.

The Automatic Transmission Input Speed Sensor?(AT ISS) Assembly is a hall-effect sensor that produces an input speed signal as the turbine shaft rotor teeth pass in front of the sensor tip.

The AT ISS is made of a permanent magnet with an iron pole piece and an integrated circuit?(IC) chip with a two-element transducer molded into a plastic housing. The two-element transducer functions as an ON/OFF switch by sensing changes in the magnetic field strength. The dual element design greatly increases the sensor's switching accuracy.

Because the turbine shaft is splined to the torque converter, it spins at engine speed. As the turbine shaft spins, the rotor teeth pass in front of the sensor tip, changing the magnetic field and creating an AC voltage. As a result, the transducers are sensing high and low magnetic signals. The IC chip will then amplify and filter the high and low signal. Therefore, whenever the engine is running, the sensor will produce high and low signals proportional to turbine shaft speed. The more rotor teeth passing by the sensor's magnetic field in a specific amount of time, the faster the turbine shaft is spinning.

The ISS assembly is attached to the pump cover with the tip of the sensor passing though the stator shaft and sleeve. The ISS mounting bolt passes through a steel insert and into a threaded hole in the pump cover. The ISS wiring harness is routed and secured to the pump cover with clip-on brackets. At the transmission control module?(TCM), the signal is electronically converted and is interpreted as transmission input speed. The TCM uses transmission input speed together with the transmission output speed to provide shift energy and torque management capabilities, improved shift quality, feel, increased TCC function, gear ratios that are more accurate and enhanced transmission diagnostics.

As the reverse clutch housing rotates, an AC voltage is induced and transmitted to the transmission control module?(TCM). The AC voltage level and the number of pulses increase as the speed of the reverse clutch housing increases. The TCM converts the AC voltage into a digital signal. The TCM uses the input shaft speed signal to help determine line pressure, transmission shift patterns, torque converter clutch?(TCC) slip speed and gear ratio.