Subaru 2002 Impreza Service Manual page 247

TRANSMISSION CONTROL MODULE (TCM)
Automatic Transmission
J: REVERSE INHIBITION CONTROL
This control prevents the transmission from shifting into the reverse gear when the select lever is
accidentally placed in the R position, thus protecting the components such as reverse clutch from
being damaged.
If the selector lever is moved to the R position during driving at a speed faster than the predeter-
mined speed, the low clutch timing solenoid is energized. Then, the pilot pressure is supplied to
the reverse inhibitor valve. This causes the reverse inhibitor valve to move downward, closing the
low & reverse brake port.
In this condition, the low & reverse brake does not engage since the ATF flowing from the manual
valve is blocked by the reverse inhibitor valve.
As a result, the transmission is put into the neutral state, and the shifting into the reverse gear is
inhibited.
r .
.
(1 )
Line pressure
(2) Pilot pressure
(3) 1 st reducing valve
(4) Shift valve A
(5) ON
NF0089
(6) Manual valve (P range) (11) Low & reverse brake (Release)
(7) Drain (12)
Low clutch
( 8 ) Shift valve B
(1 3) 2-4 brake
(9) Low clutch timing solenoid
(14)
Reverse clutch
(IO) Reverse inhibitor valve (15) High clutch
AT-25