Subaru 2002 Impreza Service Manual page 243

TRANSMISSION CONTROL MODULE (TCM)
Automatic Transmission
F: LINE-PRESSURE CONTROL DURING SHIFTING
The line pressure which engages shift clutches to create 1st to 4th speeds is controlled by the TCM
to meet varying operating conditions.
During gear shifting, the TCM decreases the line pressure to a level that matches the selected gear
in order to minimize shifting shock loads.
: Line pressure
zp;r; : Pilot pressure
: Line pressure duty pressure
: Modifier pressure
ZZZZ : Accumulator control pressure
Throttle position,
accelerator pedal
depressing speed,
etc.
NF0085
During gear shifting, the TCM controls the line pressure as follows:
0
The TCM receives signals such as throttle position signal and accelerator pedal speed signal.
Based on these input signals, it issues a control signal to the line pressure duty solenoid.
0
The pressure from the line pressure duty solenoid (line pressure duty pressure) is converted by
the pressure modifier valve into a modifier pressure, and the modifier pressure is applied to the
pressure regulator valve.
0
The pressure regulator valve adjusts the oil-pump-generated line pressure according to the
modifier pressure to make the line pressure matched to the driving condition.
AT-2 1