Theory Of Operation
WARNING: This page is about a different car, the 2005 Jeep Grand Cherokee. However, it is still accessible from the selected car via links, so may be relevant.
Communication over the CAN bus is continuously monitored between the Engine Control System and the Transmission Control System. Due to the integration of both systems into one module, (Powertrain Control Module) the bus communication between the systems is internally transmitted over the duel port ram.