Yamaha YZ250FX 2021, Owner'S Service Manual

Page: 322 / 378

FUEL INJECTION SYSTEM
8-35
Fault code No. 39
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.
“WARNING” on the Yamaha diagnostic tool blinks five times when the
injector is actuated.
Procedure
Check that injector is actuated five times by listening for the operating
sound.
Item
Probable cause of malfunc-
tion and check
Maintenance job
Confirmation of service com-
pletion
1 Connection of injector coupler.
Check the locking condition of
the coupler.
Disconnect the coupler, and
check the pins (for bent or bro-
ken terminals and locking condi-
tion of the pins).
Improperly connected

Con-
nect the coupler securely, or
repair/replace the wire harness.
Start the engine and let it idle for
approximately 5 seconds.
Check the condition of the fault
code using the malfunction
mode of the Yamaha diagnostic
tool.
Condition is “Recovered”

Go
to item 6 and finish the service.
Condition is “Detected”

Go to
item 2.
2 Defective injector. Check the injector.
Refer to “CHECKING THE
INJECTOR” on page 8-59.
Start the engine and let it idle for
approximately 5 seconds.
Check the condition of the fault
code using the malfunction
mode of the Yamaha diagnostic
tool.
Condition is “Recovered”

Go
to item 6 and finish the service.
Condition is “Detected”

Go to
item 3.
3 Connection of wire harness
ECU coupler.
Check the locking condition of
the coupler.
Disconnect the coupler, and
check the pins (for bent or bro-
ken terminals and locking condi-
tion of the pins).
Improperly connected

Con-
nect the coupler securely, or
repair/replace the wire harness.
Start the engine and let it idle for
approximately 5 seconds.
Check the condition of the fault
code using the malfunction
mode of the Yamaha diagnostic
tool.
Condition is “Recovered”

Go
to item 6 and finish the service.
Condition is “Detected”

Go to
item 4.
4 Wire harness continuity. Open or short circuit

Replace
the wire harness.
Between injector coupler and
ECU coupler.
red/black–red/black
Between injector coupler and
starter relay.
red/blue–red/blue
red/yellow–red/yellow
red–red
Start the engine and let it idle for
approximately 5 seconds.
Check the condition of the fault
code using the malfunction
mode of the Yamaha diagnostic
tool.
Condition is “Recovered”

Go
to item 6 and finish the service.
Condition is “Detected”

Go to
item 5.
5 Faulty ECU. Replace the ECU. Service is finished.