Yamaha YZ450F Owner's Service Manual page 304

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 crankshaft po-
sition sensor 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.
4 Mounted condition of crank-
shaft position sensor.
Check for looseness or
pinching.
Check the gap between the
crankshaft position sensor
and the pickup rotor.
5 Defective crankshaft position
sensor.
6 Faulty ECU
12
Crankshaft position sensor: no normal signals are received
from the crankshaft position sensor.
Unable to start engine
Unable to drive vehicle
—
—
—
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.
Between the crankshaft posi-
tion sensor coupler and ECU
coupler.
gray–gray
black/blue–black/blue
Improperly mounted sensor
 Remount or replace the
sensor. "AC MAGNETO" on
page 5-59.
Check the crankshaft position
sensor.
"CHECKING THE CRANK-
SHAFT POSITION SEN-
SOR" on page 8-42.
Replace the ECU.
8-14
FUEL INJECTION SYSTEM
Reinstatement method
Crank the engine.
Fault code No. is not dis-
played  Repair is finished.
Fault code No. is displayed 
Go to next order.
Crank the engine.
Fault code No. is not dis-
played  Repair is finished.
Fault code No. is displayed 
Go to next order.
Crank the engine.
Fault code No. is not dis-
played  Repair is finished.
Fault code No. is displayed 
Go to next order.
Crank the engine.
Fault code No. is not dis-
played  Repair is finished.
Fault code No. is displayed 
Go to next order.
Crank the engine.
Fault code No. is not dis-
played  Repair is finished.
Fault code No. is displayed 
Go to next order.