Yamaha MBK MW125 2014, Service Manual

Page: 346 / 380

FUEL INJECTION SYSTEM
8-49
Fault code No. 79
3 Wire harness continuity. Open or short circuit
→
Replace
the wire harness.
Between ISC valve coupler and
ECU coupler.
Pink–Pink
Gray–Gray
Green/yellow–Green/yellow
Sky blue–Sky blue
Set the main switch to “ON”.
Fault code number is not dis-
played
→
Service is finished.
Fault code number is displayed
→
Go to item 4.
4 Faulty ISC valve operation. Execute the diagnostic mode.
(Code No. D54)
ISC valve operation sound is
not heard.
→
Replace the ISC
valve.
Refer to “CLEANING THE ISC
(IDLE SPEED CONTROL)
UNIT AND THROTTLE BODY”
on page 7-9.
Set the main switch to “ON”.
Fault code number is not dis-
played
→
Service is finished.
Fault code number is displayed
→
Go to item 5.
5 Malfunction in ECU Replace the ECU.
Refer to “REPLACING THE
ECU (engine control unit)” on
page 8-59.
Fault code No. 61
Item ISC (idle speed control) unit: open or short circuit detected.
Fault code No. 79
Item
Engine speed is high when the Engine is idling.
Deceleration is poor when the vehicle is ridden.
Bad condition of engine or sensor.
Fail-safe system
Able to start engine
Able to drive vehicle
Diagnostic code No. 01, 03
01
Meter display
Throttle position sensor signal
• 14–20 (fully closed position)
• 97–107 (fully open position)
Procedure
• Check with throttle valve fully closed.
• Check with throttle valve fully open.
03
Meter display Displays the intake air pressure.
Procedure
Extend the sidestand, and then operate the throttle while pushing the
start switch. (If the display value changes, the performance is OK.)
Item
Probable cause of malfunc-
tion and check
Maintenance job
Confirmation of service com-
pletion
1 Locate the malfunction. Check engine idling speed. Engine idling speed is high.
→
Go to item 2.
Engine idling speed is not high.
→
Go to item 6.
2 Installed condition of YMJET
(Yamaha Mixture Jet) sub pas-
sage. Check the YMJET sub-pas-
sage for disconnections, loose-
ness, and tears. Start the engine and let it idle
for approximately 10 seconds.
Fault code number is not dis-
played
→
Service is finished.
Fault code number is displayed
→
Go to item 3.