Yamaha YZ450F Owner's Service Manual page 318

Fault code
Symptom
Fail-safe system
Diagnostic code No.
Diagnostic tool display
Procedure
Or- Probable cause of malfunc-
der tion and check
1 Faulty ECU
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 Yamaha diag-
nostic tool 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 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).
3 Wire harness continuity.
50
ECU: faulty ECU memory
Unable to start engine
Unable to drive vehicle
—
—
—
Maintenance job
Replace the ECU.
Waiting for connection
No communication signal is received from the ECU.
Able to start engine (Unable when ECU is malfunctioning)
Able to drive vehicle (Unable when ECU is malfunctioning)
—
—
—
Maintenance job
Improperly connected 
Connect the coupler secure-
ly, or repair/replace the wire
harness.
Improperly connected 
Connect the coupler secure-
ly, or repair/replace the wire
harness.
Open or short circuit  Re-
place the wire harness.
light green–light green
8-28
FUEL INJECTION SYSTEM
Reinstatement method
Turn "ON" the switch on the
FI diagnostic tool sub-lead.
Check that the fault code
number is not displayed.
Reinstatement method
Turn "ON" the switch on the
FI diagnostic tool sub-lead.
Fault code No. is not dis-
played  Repair is finished.
Fault code No. is displayed 
Go to next order.
Turn "ON" the switch on the
FI diagnostic tool sub-lead.
Fault code No. is not dis-
played  Repair is finished.
Fault code No. is displayed 
Go to next order.
Turn "ON" the switch on the
FI diagnostic tool sub-lead.
Fault code No. is not dis-
played  Repair is finished.
Fault code No. is displayed 
Go to next order.