Subaru LEGACY 2002 - 2 Electrohydraulic Control System

Automatic Transmission
ELECTROHYDRAULIC CONTROL SYSTEM
AT-8
2. VTD MODELS
The electrohydraulic control system for the transmission and transfer consists of various sensors
and switches, a transmission control module (TCM) and the hydraulic controlling units including
solenoid valves. The system controls the automatic transmission operation, including gear shift-
ing, lock-up clutch operation, line pressure, automatic control pattern selection (“Base” and “Pow-
er”), and gear-shift timing. It also controls operation of the transfer multi-plate clutch (LSD). The
TCM determines vehicle operating conditions from various input signals and controls a total of
eight solenoids (shift solenoids 1 and 2, low clutch timing solenoid, 2-4 brake timing solenoid, line
pressure duty solenoid, lock-up duty solenoid, transfer duty solenoid, and 2-4 brake duty solenoid)
by sending appropriate signals to them.
TCM
INPUT
ECM
Throttle position sensor
Rear vehicle speed sensor
Front vehicle speed sensor
Engine speed signal
HOLD switch
ECM
Intake manifold pressure signal
ECM
Torque control cut signal
Cruise control signal
POWER switch
Kickdown switch
Battery voltage
VDC communication
•ABS signal
•TCS signal
•VDC signal
•Steering angle
•Yaw-rate and lateral G signal
etc.
Brake switch
Torque converter turbine speed sensor
ATF temperature sensor
Inhibitor switch
Shift solenoid 1
OUTPUT
ON-OFF
Speedometer circuit
POWER indicator light
HOLD indicator light
Shift solenoid 2
Line pressure duty solenoid
Lock-up duty solenoid
Transfer duty solenoid
2-4 brake duty solenoid
2-4 brake timing solenoid
Low clutch timing solenoid
Torque control signal 1
ON-OFF
ECM
Torque control signal 2
ECM
AT diagnosis signal (with OBD)
Combination meter
AT OIL TEMP light
ECM
B3H2262A