Yamaha YZ 2018 Series, Owner'S Service Manual

Page: 334 / 402

FUEL INJECTION SYSTEM
8-35
TIP
• Make sure that the engine is completely cool before checking the coolant temperature sensor.
• Before troubleshooting, disconnect the starter motor lead from the starter relay.
2 Defective throttle position
sensor. Check throttle position sen-
sor signal.
Execute the diagnostic mode.
(Code No. 01)
When the throttle valve is fully
closed:
A value of 11–14 is indicated.
When throttle valve is fully
open:
A value of 109–116 is indicat-
ed.
An indicated value is out of
the specified range.

Re-
place the throttle position
sensor.
Push the start switch.
Fault code number is not dis-
played

Service is finished.
Fault code number is dis-
played

Go to item 3.
3 Malfunction in ECU. Replace the ECU.
Fault code No. 21
Item Coolant temperature sensor: open or short circuit detected.
Fail-safe system Able to start engine
Able to drive vehicle
Diagnostic code No. 06
Diagnostic tool display Displays the coolant temperature.
Procedure Compare the actually measured coolant temperature with the
Yamaha diagnostic tool display value.
Item
Probable cause of malfunc-
tion and check
Maintenance job
Confirmation of service
completion
1 Connection of coolant tem-
perature sensor coupler.
Check the locking condition
of the coupler.
Disconnect the coupler and
check the pins (bent or bro-
ken terminals and locking
condition of the pins). Improperly connected

Connect the coupler securely
or repair/replace the wire har-
ness.
Push the start switch.
Fault code number is not dis-
played

Service is finished.
Fault code number is dis-
played

Go to item 2.
2 Connection of wire harness
ECU coupler.
Check the locking condition
of the coupler.
Disconnect the coupler and
check the pins (bent or bro-
ken terminals and locking
condition of the pins). Improperly connected

Connect the coupler securely
or repair/replace the wire har-
ness.
Push the start switch.
Fault code number is not dis-
played

Service is finished.
Fault code number is dis-
played

Go to item 3.
Fault code No. 16
Item
Throttle position sensor: stuck throttle position sensor is de-
tected.