Yamaha YZ 2018 Series, Owner'S Service Manual

Page: 339 / 402

FUEL INJECTION SYSTEM
8-40
TIP
Disconnect the fuel pump coupler when this diagnostic tool is used.
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 injector five times at one-second intervals.
The engine trouble warning light and the “WARNING” on the
Yamaha diagnostic tool screen come on each time the injector is
actuated.
Procedure Check that injector is actuated five times by listening for the oper-
ating sound.
Item
Probable cause of malfunc-
tion and check
Maintenance job
Confirmation of service
completion
1 Connection of injector cou-
pler.
Check the locking condition
of the coupler.
Disconnect the coupler and
check the pins (bent or bro-
ken terminals and locking
condition of the pins). Improperly connected

Connect the coupler securely
or repair/replace the wire har-
ness.
Execute the diagnostic mode
(Code No. 36).
No operating sound

Go to
item 2.
Operating sound

Go to
item 6.
2 Defective injector. Measure the fuel injector re-
sistance.
Replace if out of specifica-
tion.
Refer to “CHECKING THE
FUEL INJECTOR” on page 8-
72. Execute the diagnostic mode
(Code No. 36).
No operating sound

Go to
item 3.
Operating sound

Go to
item 6.
3 Connection of wire harness
ECU coupler.
Check the locking condition
of the coupler.
Disconnect the coupler and
check the pins (bent or bro-
ken terminals and locking
condition of the pins). Improperly connected

Connect the coupler securely
or repair/replace the wire har-
ness.
Execute the diagnostic mode
(Code No. 36).
No operating sound

Go to
item 4.
Operating sound

Go to
item 6.
4 Wire harness continuity. Open or short circuit

Re-
place the wire harness.
Between injector coupler and
ECU coupler.
red/black–red/black
red–red/blue
Execute the diagnostic mode
(Code No. 36).
No operating sound

Go to
item 5.
Operating sound

Go to
item 6.
5 Malfunction in ECU. Replace the ECU. —
6 Delete the fault code. — Start the engine and let it idle
for approximately 5 seconds.
Check that the fault code
number is not displayed.