Yamaha XV19SX(C), Service Manual

Page: 446 / 494

FUEL INJECTION SYSTEM
7-55
Fault code No. 37 Symptom Engine speed is high when the engine is idling.
Diagnostic code No. 54 ISC valve
Order Item/components and probable
cause
Check or maintenance job Reinstatement
method
1 ECU fuse is blown. (for XV19S(C)/
XV19M(C)/ XV19CTS(C)/
XV19CTM(C)) • Check the ECU fuse. (for
XV19S(C)/ XV19M(C)/
XV19CTS(C)/ XV19CTM(C))
Refer to “CHECKING THE
FUSES” on page 7-75.
ISC valve re-
turns to its orig-
inal position by
turning the
main switch to
“ON” and back
to “OFF”.
Reinstated if
the engine idle
speed is within
specification af-
ter starting the
engine.
2 Throttle valve does not fully close. • Check the throttle bodies.
Refer to “THROTTLE BODIES”
on page 6-7.
• Check the throttle cables.
Refer to “ADJUSTING THE
THROTTLE CABLE FREE
PLAY” on page 3-8.
3 ISC valve is stuck fully open due to
disconnected ISC unit hose or cou-
pler. (High engine idle speed is de-
tected with the ISC valve stuck fully
open even though signals for the valve
to close are continuously being trans-
mitted by the ECU.) • Check that the ISC unit hose is
not disconnected.
• Check that the ISC unit coupler
is not disconnected.
• The ISC valve is stuck fully
open if it does not operate when
the main switch is turned “OFF”.
(Touch the ISC unit with your
hand and check if it is vibrating
to confirm if the ISC valve is op-
erating.)
4 ISC valve is not moving correctly. • Execute the diagnostic mode.
(Code No.54)
• After the ISC valve is fully
closed, it opens to the standby
opening position when the en-
gine is started. This operation
takes approximately 12 sec-
onds. Start the engine. If the er-
ror recurs, replace the throttle
body assembly.