Shift Control
The PCM instantaneously determines which gear should be selected by
various signals sent from sensors, and actuates the shift control
solenoid valves A and B to control shifting. Also, a Grade Logic Control
System has been adopted to control shifting in D4 position while the
vehicle is ascending or descending a slope, or reducing speed.
Lock-up Control
From sensor input signals, the PCM determines whether to turn the
lock-up ON or OFF, and activates lock-up control solenoid valve A and/
or B accordingly. The combination of driving signals to lock-up control
solenoid valves A and B and the linear solenoid pressure is shown in
the table below.
GRADE LOGIC CONTROL SYSTEM
The PCM compares actual driving conditions with driving conditions
memorized in the PCM, based on the input from the vehicle speed
sensor, the throttle position sensor, the barometric pressure sensor,
the engine coolant temperature sensor, the brake switch signal and
the shift lever position signal, to control shifting while a vehicle is
ascending or descending a slope, or reducing speed. Ascending
Control:
When the PCM determines that the vehicle is climbing a hill in position,
the system extends the engagement area of 2nd gear and 3rd gear to
prevent the transmission from frequently shifting between 2nd and 3rd
gears, and between 3rd and 4th gears, so the vehicle can run smooth
and have more power when needed. There are two ascending modes
with different 3rd gear driving areas according to the magnitude of a
gradient stored in the PCM.
The PCM memory contains shift schedules between 2nd and 3rd gears,
and between 3rd and 4th gears that enable the PCM's fuzzy logic to
automatically select the most suitable gear according to the magnitude
of a gradient.
Fuzzy logic is a form of artificial intelligence that lets computers
respond to changing conditions much like a human mind would.
When the PCM determines that the vehicle is going down a hill in
position, the shift-up speed from 3rd to 4th gear when the throttle is
closed becomes faster than the set speed for flat road driving to widen