Yamaha MBK MW125 2014 Service Manual page 346

Fault code No.
Item
3 Wire harness continuity.
4 Faulty ISC valve operation.
5 Malfunction in ECU
Fault code No. 79
Fault code No.
Item
Fail-safe system
Diagnostic code No.
Meter display
01
Procedure
Meter display
03
Procedure
Probable cause of malfunc-
Item
tion and check
1 Locate the malfunction.
2 Installed condition of YMJET
(Yamaha Mixture Jet) sub pas-
sage.
61
ISC (idle speed control) unit: open or short circuit detected.
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
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.
Replace the ECU.
Refer to "REPLACING THE
ECU (engine control unit)" on
page 8-59.
79
Engine speed is high when the Engine is idling.
Deceleration is poor when the vehicle is ridden.
Bad condition of engine or sensor.
Able to start engine
Able to drive vehicle
01, 03
Throttle position sensor signal
• 14–20 (fully closed position)
• 97–107 (fully open position)
• Check with throttle valve fully closed.
• Check with throttle valve fully open.
Displays the intake air pressure.
Extend the sidestand, and then operate the throttle while pushing the
start switch. (If the display value changes, the performance is OK.)
Maintenance job
Check engine idling speed.
Check the YMJET sub-pas-
sage for disconnections, loose-
ness, and tears.
8-49
FUEL INJECTION SYSTEM
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.
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.
Confirmation of service com-
Engine idling speed is high. →
Go to item 2.
Engine idling speed is not high.
→ Go to item 6.
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.
pletion