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
.
111
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