Subaru XT 1988 Service Manual page 553

AUTOMATIC TRANSMISSION AND DIFFERENTIAL
3-2
3-8 Electronic-Hydraulic Control System
1) OUTLINE
The electronic-hydraulic control system consists of various
sensors and switches, a transmission control unit and the
hydraulic controller including solenoid valves. The system
controls the transmission proper including shift control, lock-
up control, overrunning clutch control, line pressure control,
auto pattern select control and shift timing control. It also
controls the 4WD transfer clutch. In other words, the system
detects various operating conditions from various input signals
and sends output signals to shift solenoids 1, 2 and 3 and duty
solenoids A, Band C (a total of six solenoids for 4WD and five
solenoids for FWD).
Electronic control I/O functions
INPUT
I
Throttle opening sensor
I
Iidle switch
I
Transmission
I Vehicle revolution
sensor 1
Built in meter
I
Vehicle revolution 2
Ignition pulse
I Engine speed
I
I
ATF temperature sensor
Control unit
P, R, N, D, 3,2
I Inhibitor switch
[1st hold
I
FWD switch
(4WD)
l
Battery voltage
I Cru ise control signal
I
Fig.
62
39
r_L~I~n~i~~~u~_
-,
I ON OFF I
)
: Two solenoid are combined
: for 1 st to 4th speeds.
-
I I
I
Sh ift solenoid 1
I
I
Shift solenoid 2
:
I
Sh ift solenoid 3
I
I
I
DutY solenoid A
I
I
I
Duty solenoid B
I
I
I
Duty solenoid C
I
~
ON-OFF
J
ON-OFF
I
J
I
I
I
{ I
Engine brake control
I 3-2 shift timing control
I
: Line pressure control
I
: Lock-up control
I
I
I 4WD transfer control (4WD)
...J
r-s.:-----
2nd range monitor
~
Lights when 2nd range
, is selected
I
I
1 st hold monitor
I
i
Pattern monitor
!
I
ATF temperature
monitor
---------
Lamp output
J
I
I
Lights when 1 st hold
is selected
,
I
Lights at power pattern
, Lights when ATF
I
:J
temperature is high (4WD)
L3-641