Yamaha 2005 MT-01, Service Manual

Page: 370 / 435

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. • Check the ECU fuse.
Refer to “CHECKING THE
FUSES” on page 7-93.
ISC valve
returns to its
original position
by turning the
main switch to
“ON” and back
to “OFF”.
Reinstated if
the engine idle
speed is within
specification
after starting
the engine.
2 Throttle valve does not fully close. • Check the throttle body.
Refer to “THROTTLE BODIES”
on page 6-4.
• Check the throttle cables.
Refer to “ADJUSTING THE
THROTTLE CABLE FREE
PLAY” on page 3-7.
3 ISC valve is stuck fully open due to
disconnected ISC unit hose or
coupler. (High engine idle speed is
detected with the ISC valve stuck fully
open even though signals for the valve
to close are continuously being
transmitted 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
operating.)
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
engine is started. This
operation takes approximately
12 seconds. Start the engine. If
the error recurs, replace the
throttle body assembly.