Yamaha YZ450FP 2023, Owner'S Service Manual

Page: 327 / 388

FUEL INJECTION SYSTEM
8-28
1 Connection of coolant tempera-
ture 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).
Improperly connected

Con-
nect the coupler securely, or
repair/replace the wire harness.
Start switch to ON (no need to
start the engine), 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 2.
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).
Improperly connected

Con-
nect the coupler securely, or
repair/replace the wire harness.
Start switch to ON (no need to
start the engine), 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.
3 Wire harness continuity. Open or short circuit

Replace
the wire harness.
Between coolant temperature
sensor coupler and ECU cou-
pler.
green–green
Between coolant temperature
sensor coupler and joint con-
nector.
black–black
Between joint connector and
ECU coupler.
black/blue–black/blue
Start switch to ON (no need to
start the engine), 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.
4 Mounted condition of coolant
temperature sensor.
Check for looseness or pinch-
ing.
Check the mounted position for
correctness.
Improperly mounted sensor

Remount or replace the sensor.
Start switch to ON (no need to
start the engine), 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.
5 Defective coolant temperature
sensor.
Execute the diagnostic mode.
(Code No. 06)
Proper display:
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.
Start switch to ON (no need to
start the engine), 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.
6 Faulty ECU. Replace the ECU. Service is finished.
7 Delete the fault code. Confirm that the fault code has
a condition of “Recovered”
using the Yamaha diagnostic
tool, and then delete the fault
code.
Fault code No. 21
Item Coolant temperature sensor: open or short circuit detected.