Toyota COMPUTER-CONTROLLED SYSTEM Training Manual page 123

ISC - Functions of Engine EC U
4 . ON-OFF CONTROL VSV TYPE ISC VALV E
The Engine ECU sends signals to the VSV, in
accordance with signals from various sensors, to
cause the engine to idle at the appropriate
speed .
Battery
During warm-up, the fast-idle speed is
controlled by the air valve .
The following diagram shows one example of
connections between the VSV and ECU .
CONDITIONS FOR VSV OPERATION
a . Off to O n
• When the engine is cranking and immediately
after starting .
• When engine speed falls below a
predetermined rpm (depending on the neutral
sta rt switch signal) with the idle contact on* .
• Several seconds after shifting from "P" or
"N" into any other range with the idle contact
on (A/T vehicles) . *
• The light control switch is turned on .
• The rear window defogger switch is turne d
on .
* The VSV stays off under this condition if check
terminals T or TE1 is connected to El .
However, if the light control switch or rear win-
dow defogger switch is turned on, the VSV
goes on .
OHP 7 8
b . On to Of f
• When a predetermined period of time has
elapsed after the engine has started .
• When engine speed rises above a
predetermined rpm (depending on the neutral
start switch signal) with the idle contact on
and the A/C magnetic clutch disengaged .
• After a set time has elapsed after the
transmission is shifted from "P" or "N" into
any other range and the engine speed is
above a predetermined rpm with the idle
contact on and the A/C magnetic clutch
disengaged (A/T vehicles) .
• The light control switch is turned off.
• The rear window defogger switch is turned
off .
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