Subaru 2002 Impreza Service Manual page 245

TRANSMISSION CONTROL MODULE (TCM)
Automatic Transmission
H: GRADE CONTROL
While the vehicle is driving up a hill, the gear is fixed to the 3rd to avoid repeated gear shift between
the 3rd and 4th gears.
When the vehicle is descending a steep slope at a speed of approximately 80 km/hour (50 miles/
hour), a 4th to 3rd downshift occurs automatically when the brake pedal is depressed.
This gearshift control is cancelled when the accelerator pedal is depressed.
The TCM performs these controls based mainly on the throttle opening, engine speed and vehicle
speed.
WI
r -
-
BRAKEPEDAL
ON
RE-ACCELERATION
"D" range (Base pattern)
Throttle
openin(
NF0087
"D" range (Grade control pattern)
Throttle
opening
0 Vehicle speed
NF0088
AT-23