Yamaha YZ450F(E) 2014 Owner's Service Manual page 315

Fault code
Symptom
4 Connection of sub wire har-
ness 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).
5 Wire harness continuity.
6 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 Faulty ECU
39
Injector: open or short circuit detected.
Improperly connected 
Connect the coupler secure-
ly, or repair/replace the sub-
wire harness.
Open or short circuit  Re-
place the wire harness.
Between injector coupler and
ECU coupler.
red/black–red/black
Between injector coupler and
rectifier/regulator coupler
red/red
Replace the ECU.
41
ECU: built-in lean angle sensor malfunction
Unable to start engine
Able to drive vehicle
08
Displays the lean angle sensor output voltage.
• 1.0 V (upright)
• 4.0 V (overturned)
Remove the ECU, and incline it 45° or more.
Maintenance job
Replace the ECU.
8-25
FUEL INJECTION SYSTEM
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.
Reinstatement method