Yamaha YZ 2020 Series Owner's Service Manual page 321

Fault code No.
Item
6 Defective ignition coil. (test the
primary coils for continuity)
7 Faulty ECU.
8 Delete the fault code.
Fault code No. 39
TIP
Disconnect the fuel pump coupler when this diagnostic tool is used.
Fault code No.
Item
Fail-safe system
Diagnostic code No.
Actuation
Procedure
Probable cause of malfunc-
Item
tion and check
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).
33
Ignition coil: open or short circuit detected in the primary lead of
the ignition coil.
Check the primary resistance of
the ignition coil.
Refer to "CHECKING THE
IGNITION COIL" on page 8-52.
Execute the diagnostic mode.
(Code No. 30)
No spark  Replace the ECU.
Confirm that the fault code has
a condition of "Recovered"
using the Yamaha diagnostic
tool, and then delete the fault
code.
39
Injector: open or short circuit detected.
Unable to start engine
Unable to drive vehicle
36
Actuates injector five times at one-second intervals.
"WARNING" on the Yamaha diagnostic tool blinks five times when the
injector is actuated.
Check that injector is actuated five times by listening for the operating
sound.
Maintenance job
Improperly connected  Con-
nect the coupler securely, or
repair/replace the wire harness.
8-34
FUEL INJECTION SYSTEM
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 8 and finish the service.
Condition is "Detected"  Go to
item 7.
Service is finished.
Confirmation of service com-
pletion
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.