Yamaha YZ450F Owner's Service Manual page 319

Fault code
Symptom
Fail-safe system
Diagnostic code No.
Diagnostic tool display
Procedure
Or- Probable cause of malfunc-
der tion and check
1 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).
2 Wire harness continuity.
3 Faulty AC magneto
4 Faulty ECU
46
Vehicle system power supply: normal voltage is not supplied
to the ECU.
Able/Unable to start engine
Able/Unable to drive vehicle
—
—
—
Maintenance job
Improperly connected 
Connect the coupler secure-
ly, or repair/replace the wire
harness.
Open or short circuit  Re-
place the wire harness.
Between rectifier/regulator
and ECU coupler
red–red
Between condenser and
ECU coupler
red–red
Check the AC magneto.
"CHECKING THE AC MAG-
NETO" on page 5-62.
Replace the ECU.
8-27
FUEL INJECTION SYSTEM
Reinstatement method
After starting the engine, idle
this, turn "OFF" the switch on
the FI diagnostic tool sub-
lead, and wait about 5 sec-
onds or more.
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, turn "OFF" the switch on
the FI diagnostic tool sub-
lead, and wait about 5 sec-
onds or more.
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, turn "OFF" the switch on
the FI diagnostic tool sub-
lead, and wait about 5 sec-
onds or more.
Fault code No. is not dis-
played  Repair is finished.
Fault code No. is displayed 
Go to next order.