Yamaha YZ450F(D) Owner's Service Manual page 190

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.
OK ↓
*Check AC magneto.
OK ↓
Check ECU. (Throttle position sensor input volt-
age)
*marked: Refer to "IGNITION SYSTEM" section.
Use the following special tools in this inspection.
Model 88 Multimeter with tacometer:
YU-A1927
Digital circuit tester:
90890-03174
Test harness-speed sensor (3P):
YU-03208/90890-03208
THROTTLE POSITION SENSOR SYSTEM
No good → Repair or replace.
No good → Replace.
No good → Replace.
No good →
Replace.
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