Controller Area Network (Can)
The Transmission Control Module (TCM) is a CAN based control module. It can communicate directly with all the other CAN users, those being the traction control unit, the ECM and the instrument pack. In addition to vehicle data (i.e. data about vehicle conditions, e.g. engine speed) the network carries data specifically for error checking of the vehicle data messages. The TCM uses this data to confirm that the communications network is functioning correctly.
The TCM forms a bi-directional terminated node on a twisted pair ring bus configuration. This configuration requires all CAN users to be connected at all times, as each unit completes the ring. The TCM will not operate correctly without CAN present. If messages that are expected by the TCM are not being received (all modules transmit some data on a regular basis) or messages are proven to be repeatedly corrupt, the TCM will register an appropriate network failure. If the failure is identified on two consecutive drive cycles then the appropriate DTC is logged.
If the table does not include details of the following enabling conditions: intake air and engine coolant temperature, vehicle speed range, and time after engine start-up then the state of these parameters has no influence upon the execution of the monitor. See Fig 1 .