Automatic Transaxle Input Speed Sensor (A/T ISS)

The A/T input speed sensor (ISS) is a magnetic inductive pickup that relays information about the transaxle input speed to the transmission control module (TCM). The TCM uses this information to perform the following functions:

• Controls line pressure
• Controls torque converter clutch (TCC) apply and release
• Controls transaxle shift patterns
• Calculates the appropriate operating gear ratios
• Calculates TCC slippage

Fig 1: View Of Automatic Transaxle Input Speed Sensor

Courtesy of GENERAL MOTORS CORP.

The ISS mounts onto piston B the valve body. An air gap of 1.8-2.2 mm (0.070-0.086 in) is maintained between the sensor and piston B. The sensor consists of a permanent magnet surrounded by a coil of wire. As piston B is driven by the turbine shaft, the ISS induces an AC signal.

Higher vehicle speeds induce a higher frequency and a higher voltage measurement at the sensor. Sensor resistance should measure between 825-835Ω at 20°C (68°F). The sensor can measure between 1,000-8,000 Hz.