Yamaha WR450FN 2022 Owner's Service Manual page 339

Fault code No.
Item
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 coolant
temperature sensor.
Check for looseness or pinch-
ing.
Check the mounted position for
correctness.
5 Defective coolant temperature
sensor.
6 Faulty ECU.
7 Delete the fault code.
21
Coolant temperature sensor: open or short circuit detected.
Improperly connected  Con-
nect the coupler securely, or
repair/replace the wire harness.
Open or short circuit  Replace
the wire harness.
Between coolant temperature
sensor coupler and ECU cou-
pler.
green/white–green/white
black/blue–black/blue
Improperly mounted sensor 
Remount or replace the sensor.
Execute the diagnostic mode.
(Code No. 06)
When the machine is cold, dis-
played temperature is close to
the ambient temperature.
Improper display  Replace the
coolant temperature sensor.
Refer to "RADIATOR" on page
6-2.
Replace the ECU.
Confirm that the fault code has
a condition of "Recovered"
using the Yamaha diagnostic
tool, and then delete the fault
code.
8-40
FUEL INJECTION SYSTEM
Push the start switch (main
relay ON), and then check the
condition of the fault code using
the malfunction mode of the
Yamaha diagnostic tool.
Condition is "Recovered"  Go
to item 7 and finish the service.
Condition is "Detected"  Go to
item 3.
Push the start switch (main
relay ON), and then check the
condition of the fault code using
the malfunction mode of the
Yamaha diagnostic tool.
Condition is "Recovered"  Go
to item 7 and finish the service.
Condition is "Detected"  Go to
item 4.
Push the start switch (main
relay ON), and then check the
condition of the fault code using
the malfunction mode of the
Yamaha diagnostic tool.
Condition is "Recovered"  Go
to item 7 and finish the service.
Condition is "Detected"  Go to
item 5.
Push the start switch (main
relay ON), and then check the
condition of the fault code using
the malfunction mode of the
Yamaha diagnostic tool.
Condition is "Recovered"  Go
to item 7 and finish the service.
Condition is "Detected"  Go to
item 6.
Service is finished.