MODULE-TRANSMISSION CONTROL
DESCRIPTION
3.7L VEHICLES
The
transmission
control
module
(TCM)
(1)
is
mounted to the dash panel (2), under the dash panel
silencer pad, just to the right of the steering column.
The electronic control system consists of various components providing inputs to the TCM. The TCM monitors trans-
mission sensors, shifter assembly, and bus messages to determine transmission shift strategy. 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 communi-
cation 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 trans-
mission 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 sole-
noid 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).
8E - 282
ELECTRONIC CONTROL MODULES - SERVICE INFORMATION
WK