Circuit Description
WARNING: This page is about a different car, the 2007 Saturn Vue. However, it is still accessible from the selected car via links, so may be relevant.
The engine control module (ECM) receives vehicle speed through high-speed communications on the controller area network (CAN) from the transmission control module (TCM) based on the output speed sensor (OSS). The OSS is attached to the top rear of the transmission case. The sensor produces an AC current generated as the output shaft rotates. The ECM continuously monitors the vehicle speed signal supplied by the TCM.
If the ECM does not detect a sufficient amount of vehicle speed from the TCM over the CAN link when engine speed is above a certain range while the vehicle is in fourth of fifth gear, DTC P0502 sets. DTC P0502 is a type B DTC.