Description And Operation: Description
- The Transmission Control Module (TCM) (1) is mounted on the outside of the transmission case, over the differential.
- The electronic control system consists of various components providing inputs to the TCM. The TCM monitors transmission sensors, shifter assembly, and bus messages to determine transmission shift strategy.
1 - TCM - After shift strategies are determined, the TCM controls the actuation of transmission solenoids, which controls the routing of hydraulic fluid within the transmission, by moving a sequence of four valves to make a shift occur.
- The system performs its functions based on continuous real-time sensor feedback information.
- In addition the TCM receives information from the rest of the vehicle over the CAN C bus. The CAN C bus is a high-speed communication bus that allows real time control capability between various controllers.
- Most messages are sent every 20 milliseconds. This means critical information can be shared between the transmission, engine, and ABS controllers.
- The CAN C bus is a two wire bus with a CAN C Bus (+) circuit and a CAN C Bus (-) circuit. These circuits are twisted pairs in the harness to reduce the potential of radio and noise interference.
- The transmission control system automatically adapts to changes in engine performance, vehicle speed, and transmission temperature variations to provide consistent shift quality.
- The control system ensures that clutch operation during up shifting and downshifting is more responsive without increased harshness.
- The TCM activates the solenoid valves and moves valves in the valve body to achieve the necessary gear changes.
- The required pressure level is calculated from the load condition, engine speed.
- Vehicle speed (from ABS module) and transmission oil temperature, matched to the torque to be transmitted.
- Power for the transmission system is supplied through the shifter mechanism (no transmission control relay).