Yamaha WR450FX Owner's Service Manual page 212

THROTTLE POSITION SENSOR SYSTEM
INSPECTION STEPS
If the throttle position sensor will not operate, use the following inspection steps.
Check entire ignition system for connection.
↓
OK
Check throttle position sensor.(Throttle position
sensor coil)
↓
OK
Check CDI unit.(Throttle position sensor input
voltage)
Use the following special tools in this inspection.
Pocket tester:
YU-3112-C/90890-03112
THROTTLE POSITION SENSOR SYSTEM
→
No good Repair or replace.
→
No good
Replace.
→
No good
Replace.
7-15