Toyota Celica Supra 1986 Service And Repair Manual page 282

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AUTOMATIC TRANSMISSION - Electric Control AT·7
TROUBLESHOOTING OF ELECTRICAL CONTROL
CIRCUIT
O.acription
1. A self-diagnosis function is built into the electrical control
system. Warning is indicated by the overdrive OFF indica·
tor light.
NOTE: Warning and diagnostic codes can be read only
when the overdrive switch is ON. If OFF,the overdrive light
is tit continuously and will not blink.
tal II a malfunction occurs within the speed sensors (No.
1 or
21
or solenoids (No.1 or
2},
the overdrive OFF tight
will blink to warn the driver.
However. there
will be
no warning of a malfunction
with solenoid No. 3 .
{bl The diagnostic code can be read by the number of
blinks of the overdrive indicator light when OG termi-
nal and body ground are short-circuited. !See page
A T·8)
lcl The throttle position sensor or brake signal are not in·
dicat ed, but inspection can be made by checking the
voltage at DG terminal.
ldl The signals to each gear can be checked by measur·
ing the voltage at
OG
terminal.
2.
The diagnostic code ltrO<Jble code) is retained in memory
by the CPU tof ECT ECUI and due to back-up voltage, is
not c. a nceled out when the engine is turned
oft.
Conse-
quently. after repair,
it
is necessary to turn tho ignition
switch off and remove the luse STOP I 15A} or disconnect
the ECT ECU connector to cancel out the diagnostic ltrou·
blel code. tSee page AT- 101
NOTE:
• Low battery voltage will cause faulty operation of
tt\e
diagnosis system . Therefore, always ch.eck the battery
first.
• Use a voltmeter and ohmmeter that have an impedance
of at least 10 KQ/V.