Yamaha YZ450F Owner's Service Manual page 314

Fault code
Symptom
6 Faulty ECU
TIP
Disconnect the fuel pump coupler when this diagnostic tool is used.
Fault code
Symptom
Fail-safe system
Diagnostic code No.
Actuation
Procedure
Or- Probable cause of malfunc-
der tion and check
1 Connection of injector cou-
pler.
Check the locking condition
of the coupler.
Disconnect the coupler, and
check the pins (for bent or
broken terminals and locking
condition of the pins).
2 Defective injector.
3 Connection of wire harness
ECU coupler.
Check the locking condition
of the coupler.
Disconnect the coupler, and
check the pins (for bent or
broken terminals and locking
condition of the pins).
33
Ignition coil: open or short circuit detected in the primary lead
of the ignition coil.
Execute the diagnostic mode.
(Code No. 30)
No spark  Replace the
ECU.
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 oper-
ating sound.
Maintenance job
Improperly connected 
Connect the coupler secure-
ly, or repair/replace the wire
harness.
Check the injector.
"CHECKING THE FUEL IN-
JECTOR" on page 8-47.
Improperly connected 
Connect the coupler secure-
ly, or repair/replace the wire
harness.
8-24
FUEL INJECTION SYSTEM
Reinstatement method
After starting the engine, idle
this and wait about 5 sec-
onds.
Fault code No. is not dis-
played  Repair is finished.
Fault code No. is displayed 
Go to next order.
After starting the engine, idle
this and wait about 5 sec-
onds.
Fault code No. is not dis-
played  Repair is finished.
Fault code No. is displayed 
Go to next order.
After starting the engine, idle
this and wait about 5 sec-
onds.
Fault code No. is not dis-
played  Repair is finished.
Fault code No. is displayed 
Go to next order.