Yamaha YZ 2023 Series Owner's Service Manual page 314

Fault code No. 15
TIP
Before troubleshooting, disconnect the starter motor lead from the starter relay.
Fault code No.
Item
Fail-safe system
Diagnostic code No.
Diagnostic tool display
Procedure
Probable cause of malfunc-
Item
tion and check
1 Connection of throttle position
sensor coupler.
Check the locking condition of
the coupler.
Disconnect the coupler, and
check the pins (for bent or bro-
ken terminals and locking condi-
tion 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 bro-
ken terminals and locking condi-
tion of the pins).
3 Wire harness continuity.
4 Mounted condition of throttle
position sensor.
Check for looseness or pinch-
ing.
Check the mounted position for
correctness.
15
Throttle position sensor: open or short circuit detected.
Able to start engine
Able to drive vehicle
01
Displays the throttle angle.
• 11–14 (throttle in fully closed position)
• 86–92 (throttle in fully opened position)
• Check with throttle fully closed.
• Check with throttle fully opened.
Maintenance job
Improperly connected  Con-
nect the coupler securely, or
repair/replace the wire harness.
Improperly connected  Con-
nect the coupler securely, or
repair/replace the wire harness.
Open or short circuit  Replace
the wire harness.
Between throttle position sensor
coupler and ECU coupler.
yellow–yellow
blue–blue
black/blue–black/blue
Improperly mounted sensor 
Remount or replace the sensor.
Refer to "ADJUSTING THE
THROTTLE POSITION SEN-
SOR" on page 7-8.
8-27
FUEL INJECTION SYSTEM
Confirmation of service com-
pletion
Start switch to ON (main relay
ON), and then check the condi-
tion of the fault code using the
malfunction mode of the
Yamaha diagnostic tool.
Condition is "Recovered"  Go
to item 8 and finish the service.
Condition is "Detected"  Go to
item 2.
Start switch to ON (main relay
ON), and then check the condi-
tion of the fault code using the
malfunction mode of the
Yamaha diagnostic tool.
Condition is "Recovered"  Go
to item 8 and finish the service.
Condition is "Detected"  Go to
item 3.
Start switch to ON (main relay
ON), and then check the condi-
tion of the fault code using the
malfunction mode of the
Yamaha diagnostic tool.
Condition is "Recovered"  Go
to item 8 and finish the service.
Condition is "Detected"  Go to
item 4.
Start switch to ON (main relay
ON), and then check the condi-
tion of the fault code using the
malfunction mode of the
Yamaha diagnostic tool.
Condition is "Recovered"  Go
to item 8 and finish the service.
Condition is "Detected"  Go to
item 5.