Circuit Description
WARNING: This page is about a different car, the 2003 Saturn LW300, 2003 Saturn LW200, 2003 Saturn L300, and 2003 Saturn L200. However, it is still accessible from the selected car via links, so may be relevant.
The automatic transmission output shaft speed sensor (AT OSS) provides vehicle speed information to the TCM. The AT OSS is a permanent magnet generator mounted to the transmission case. The AT OSS produces an AC voltage as the transmission speed sensor rotor teeth pass through the magnetic field of the sensor. The AC voltage level increases as the speed of the vehicle increases. The TCM converts the AC voltage into a digital signal. The TCM uses the vehicle speed signal to determine shift timing, torque converter clutch (TCC) apply, TCC release, and gear ratio calculations.
When the TCM detects a low output speed and the vehicle has a large engine speed in a drive gear, then DTC P0502 sets. DTC P0502 is a type B DTC.