Automatic Transmission; Electrohydraulic Control System - Subaru 2002 Impreza Service Manual

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FWD indicator light (non-turbo model)
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meter
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AT OIL TEMP light
ELECTROHYDRAULIC CONTROL SYSTEM
Automatic Transmission
1. Electrohydraulic Control System
A: GENERAL
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.
INPUT
OUTPUT
ON-OFF
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Throttle position sensor
t-
Shift solenoid 1
ON-OFF
Shift solenoid 2
Line pressure duty solenoid
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ECM 4
Dropping resistor A (non-turbo model)
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4
Lock-up duty solenoid
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4
Transfer duty solenoid
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Inhibitor switch
t-
ECM
I n t a k e -
(non-turbo model)
ECM
TCM
Mass air flow signal (turbo model)
4
2-4 brake timing solenoid
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FWD switch (non-turbo model)
t--.
Low clutch timing solenoid
ECM
Torque control signal 1
FCM
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Battery voltage
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ABS signal
k
4
Torque control signal 2
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Brake switch
t-
4
AT diagnosis signal
~
ECM
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Cruise control signal
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NF0464
AT-2