Yamaha XMAX 125, Service Manual

Page: 442 / 498

FUEL INJECTION SYSTEM
8-45
Fault code No. 37
Item ISC valve: engine speed is high when the engine is idling.
Fail-safe system
Able to start engine
Able to drive vehicle
Diagnostic code No. 54
Actuation
Actuates and fully closes the ISC valve, then opens it to the stand-
by opening position when the engine is started.
This operation takes approximately 12 seconds until it is complet-
ed.
Checking method The ISC unit vibrates when the ISC valve operates.
Probable cause of malfunction Check or maintenance job
1 Throttle valve does not fully close. • Check the throttle body.
Refer to “THROTTLE BODY” on page 7-5.
• Check the throttle cables.
Refer to “ADJUSTING THE THROTTLE CA-
BLE FREE PLAY” on page 3-9 and “ADJUST-
ING THE THROTTLE CABLE FREE PLAY” on
page 3-23.
2 ISC valve is stuck fully open due to dis-
connected ISC unit 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 coupler is not discon-
nected.
• 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.)
3 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 re-
curs, replace the throttle body assembly.
Reinstatement method
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.
Fault code No. 39
Item Injector: open or short circuit detected.
Fail-safe system
Unable to start engine
Unable to drive vehicle
Diagnostic code No. 36
Actuation
Actuates the injector five times at one-second intervals.
Illuminates the “WARNING” LED on the FI diagnostic tool and the
engine trouble warning light.
Checking method
Check that the injector actuates five times by listening to the oper-
ating sound.