Subaru LEGACY 2002 - 2. Electrohydraulic Control System

Automatic Transmission
ELECTROHYDRAULIC CONTROL SYSTEM
AT-7
2. Electrohydraulic Control System
A: GENERAL
1. MPT 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 the operation of the transfer clutch. 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 sole-
noid, lock-up duty solenoid, transfer duty solenoid, and 2-4 brake duty solenoid) by sending ap-
propriate 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
FWD switch
Battery voltage
ABS signal
Brake switch
Torque converter turbine speed sensor
ATF temperature sensor
Inhibitor switch
Shift solenoid 1
OUTPUT
ON-OFF
Speedometer circuit
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)
FWD indicator light
Combination meter
AT OIL TEMP light
POWER indicator light
HOLD indicator light
ECM
B3H2271
A