Circuit/System Description

The transmission control module (TCM) sends vehicle speed data to the engine control module (ECM). The data is sent to the ECM through a high speed network called the GM control area network (CAN). Two circuits are used to communicate CAN data between the ECM and TCM. A fault in the CAN will not cause DTC P0864 to set by itself. If a CAN fault occurs, other DTCs set before DTC P0864.