Input And Output Speed Sensor Assembly (A/T)

The input and output speed sensor assembly is mounted inside the transmission, under the control valve body cover. Both sensors are variable reluctance magnetic pickups and are wired into the same connector, which plugs into the control solenoid valve assembly. The sensors consist of a permanent magnet surrounded by a coil of wire. The Vehicle Speed Sensor (VSS) is a Permanent Magnet (PM) generator mounted in transaxle/transmission.

The ISS is positioned next to the input speed sensor reluctor ring assembly and has an air gap of 0.045-0.109" (1.143-2.77 mm) between the reluctor ring teeth and the magnetic pickup. As the input speed sensor reluctor ring assembly rotates, an Alternating Current (AC) is induced in the coil by the "teeth" on the reluctor ring as they pass by the magnetic pickup. Therefore, whenever the turbine shaft, input shaft assembly, is turning, the ISS produces an AC voltage signal proportional to turbine speed. At the Transmission Control Module (TCM), the AC signal is electronically conditioned to a 5-volt square wave form. The square wave form can then be interpreted as transmission input speed by the TCM through the frequency of square waves in a given time frame. The square waves can be thought of as a representation of the reluctor ring teeth. Therefore, the more teeth, or waves, that pass by the magnetic pickup in a given time frame, the faster the turbine shaft is turning. The square wave form is compared to a fixed clock signal within the TCM to determine transmission input speed.

The Output Speed Sensor (OSS) operates identically to the ISS sensor except that it uses the teeth of the parking lock gear as the rotor, reluctor. The parking lock gear is splined to the variable driven pulley assembly. The OSS has an air gap of 0.045-0.109" (1.143-2.77 mm) between the teeth and the magnetic pickup. The OSS sensor square wave form is also compared to a fixed clock signal within the TCM to determine actual vehicle speed. The TCM uses transmission input and output speeds to help determine line pressure, transmission ratio control patterns and TCC apply pressure and timing. This speed sensor information is also used to calculate turbine speed, drive ratios, and TCC slippage for diagnostic purposes.