2016 YAMAHA WR 450F engine

FUEL INJECTION SYSTEM
9-42
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.
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 jobConfirmation 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.
3 Wire harness continuity. Open or short circuit  Re-
place the wire harness.
Between coolant temperature
sensor coupler and ECU cou-
pler.
green/white–green/white
black/blue–black/blue Push the start switch.
Fault code number is not dis-
played
 Service is finished.
Fault code number is dis-
played  Go to item 4.
4 Installed condition of coolant temperature sensor.
Check for looseness or
pinching. Improperly installed sensor

Reinstall or replace the
sensor. Push the start switch.
Fault code number is not dis-
played
 Service is finished.
Fault code number is dis-
played  Go to item 5.

FUEL INJECTION SYSTEM
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TIP
• Make sure that the engine is completely cool before checking the intake air temperature sensor.
• Before troubleshooting, disconnect the starter motor lead from the starter relay.
5 Defective coolant tempera-
ture sensor. Execute the diagnostic mode.
(Code No. 06)
When engine is cold:
Displayed temperature is
close to the ambient temper-
ature.
The displayed temperature is
not close to the ambient tem-
perature. 
Check the cool-
ant temperature sensor.
Replace if defective.
Refer to “CHECKING THE
COOLANT TEMPERATURE
SENSOR” on page 9-78. Push the start switch.
Fault code number is not dis-
played
 Service is finished.
Fault code number is dis-
played  Go to item 6.
6 Malfunction in ECU. Replace the ECU.
Fault code No. 22
Item Intake air temperature sensor: open or short circuit detected.
Fail-safe system Able to start engine
Able to drive vehicle
Diagnostic code No. 05
Diagnostic tool display Displays the intake air temperature.
Procedure Compare the actually measured intake air temperature with the
Yamaha diagnostic tool display value.
Item Probable cause of malfunc-
tion and check Maintenance jobConfirmation of service
completion
1 Connection of intake air 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. 21
Item Coolant temperature sensor: open or short circuit detected.

FUEL INJECTION SYSTEM
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TIP
Before troubleshooting, disconnect the starter motor lead from the starter relay.
3 Wire harness continuity. Open or short circuit
 Re-
place the wire harness.
Between intake air tempera-
ture sensor coupler and ECU
coupler.
black/blue–black/blue
brown/white–brown/white Push the start switch.
Fault code number is not dis-
played
 Service is finished.
Fault code number is dis-
played  Go to item 4.
4 Installed condition of intake air temperature sensor.
Check for looseness or
pinching. Improperly installed sensor

Reinstall or replace the
sensor. Push the start switch.
Fault code number is not dis-
played
 Service is finished.
Fault code number is dis-
played  Go to item 5.
5 Defective intake air tempera- ture sensor. Execute the diagnostic mode.
(Code No. 05)
When engine is cold:
Displayed temperature is
close to the ambient temper-
ature.
The displayed temperature is
not close to the ambient tem-
perature.
 Check the intake
air temperature sensor.
Replace if defective.
Refer to “CHECKING THE
INTAKE AIR TEMPERA-
TURE SENSOR” on page 9-
80. Push the start switch.
Fault code number is not dis-
played
 Service is finished.
Fault code number is dis-
played  Go to item 6.
6 Malfunction in ECU. Replace the ECU.
Fault code No. 30
Item Latch up detected.
Fail-safe system Unable to start engine
Unable to drive vehicle
Diagnostic code No. 08
Diagnostic tool display Lean angle sensor output voltage
• 0.4–1.4 (upright)
• 3.7–4.4 (overturned)
Procedure Remove the lean angle sensor and incline it more than 45 degrees.
Item Probable cause of malfunc-
tion and check Maintenance jobConfirmation of service
completion
1 The vehicle has overturned. Raise the vehicle upright. Push the start switch. Fault code number is not dis-
played  Service is finished.
Fault code number is dis-
played  Go to item 2.
Fault code No.
22
Item Intake air temperature sensor: open or short circuit detected.

FUEL INJECTION SYSTEM
9-45
2 Installed condition of lean an-gle sensor. Check the installed direction
and condition of the 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 Defective lean angle sensor. Execute the diagnostic mode. (Code No. 08)
Replace if defective.
Refer to “CHECKING THE
LEAN ANGLE SENSOR” on
page 9-75.Push the start switch.
Fault code number is not dis-
played
 Service is finished.
Fault code number is dis-
played  Go to item 4.
4 Malfunction in ECU. Replace the ECU.
Fault code No. 33
Item Ignition coil: open or short circuit detected in the primary lead
of the ignition coil.
Fail-safe system Unable to start engine
Unable to drive vehicle
Diagnostic code No. 30
Actuation Actuates the ignition coil five times at one-second intervals.
The engine trouble warning light and the “WARNING” on the
Yamaha diagnostic tool screen come on each time the ignition coil
is actuated.
Procedure Check that a spark is generated five times.
• Connect an ignition checker.
Item Probable cause of malfunc-
tion and check Maintenance jobConfirmation of service
completion
1 Connection of ignition coil 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. Start the engine and let it idle
for approximately 5 seconds.
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. Start the engine and let it idle
for approximately 5 seconds.
Fault code number is not dis-
played
 Service is finished.
Fault code number is dis-
played  Go to item 3.
Fault code No.
30
Item Latch up detected.

FUEL INJECTION SYSTEM
9-46
3 Connection of sub wire har-ness coupler.Check the lock-
ing condition of the
coupler.Disconnect the cou-
pler and check the pins (bent
or broken terminals and lock-
ing condition of the pins). Improperly connected

Connect the coupler secure-
lyor repair/replace the sub
wire harness. Start the engine and let it idle
for approximately 5 seconds.
Fault code number is not dis-
played
 Service is finished.
Fault code number is dis-
played  Go to item 4.
4 Wire harness continuity. Open or short circuit  Re-
place the wire harness.
Between ignition coil coupler
and ECU coupler.
orange–orange Start the engine and let it idle
for approximately 5 seconds.
Fault code number is not dis-
played
 Service is finished.
Fault code number is dis-
played  Go to item 5.
5 Installed condition of ignition coil.
Check for looseness or
pinching. Improperly installed sensor

Reinstall or replace the
sensor. Start the engine and let it idle
for approximately 5 seconds.
Fault code number is not dis-
played
 Service is finished.
Fault code number is dis-
played  Go to item 6.
6 Defective ignition coil. (test the primary coils for continu-
ity) Check the ignition coil.
Replace if defective.
Refer to “CHECKING THE
IGNITION COIL” on page 9-
74. Start the engine and let it idle
for approximately 5 seconds.
Fault code number is not dis-
played
 Service is finished.
Fault code number is dis-
played  Go to item 7.
7 Malfunction in ECU. Execute the diagnostic mode (diagnostic code No. 30).
No spark  Replace the
ECU.
Fault code No. 33
Item
Ignition coil: open or short circuit detected in the primary lead
of the ignition coil.

FUEL INJECTION SYSTEM
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TIP
Disconnect the fuel pump coupler when this diagnostic tool is used.
Fault code No. 39
Item Injector: open or short circuit detected.
Fail-safe system Unable to start engine
Unable to drive vehicle
Diagnostic code No. 36
Actuation Actuates injector five times at one-second intervals.
The engine trouble warning light and the “WARNING” on the
Yamaha diagnostic tool screen come on each time the injector is
actuated.
Procedure Check that injector is actuated five times by listening for the oper-
ating sound.
Item Probable cause of malfunc-
tion and check Maintenance jobConfirmation of service
completion
1 Connection of injector cou- pler.
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. Execute the diagnostic mode
(Code No. 36).
No operating sound
 Go to
item 2.
Operating sound  Go to
item 6.
2 Defective injector. Measure the fuel injector re- sistance.
Replace if out of specifica-
tion.
Refer to “CHECKING THE
FUEL INJECTOR” on page 9-
81.Execute the diagnostic mode
(Code No. 36).
No operating sound
 Go to
item 3.
Operating sound  Go to
item 6.
3 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. Execute the diagnostic mode
(Code No. 36).
No operating sound
 Go to
item 4.
Operating sound  Go to
item 6.
4 Wire harness continuity. Open or short circuit  Re-
place the wire harness.
Between injector coupler and
ECU coupler.
red/black–red/black
red–red/blue Execute the diagnostic mode
(Code No. 36).
No operating sound
 Go to
item 5.
Operating sound  Go to
item 6.
5 Malfunction in ECU. Replace the ECU. —
6 Delete the fault code. — Start the engine and let it idle for approximately 5 seconds.
Check that the fault code
number is not displayed.

FUEL INJECTION SYSTEM
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TIP
Before troubleshooting, disconnect the starter motor lead from the starter relay.
Fault code No. 41
Item Lean angle sensor: open or short circuit detected.
Fail-safe system Unable to start engine
Able to drive vehicle
Diagnostic code No. 08
Diagnostic tool display Lean angle sensor output voltage
• 0.4–1.4 (upright)
• 3.7–4.4 (overturned)
Procedure Remove the lean angle sensor and incline it more than 45 degrees.
Item Probable cause of malfunc-
tion and check Maintenance jobConfirmation of service
completion
1 Connection of lean angle 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.
3 Wire harness continuity. Open or short circuit  Re-
place the wire harness.
Between lean angle sensor
coupler and ECU coupler.
blue–blue
yellow/green–yellow/green
black/blue–black/blue Push the start switch.
Fault code number is not dis-
played
 Service is finished.
Fault code number is dis-
played  Go to item 4.
4 Defective lean angle sensor. Execute the diagnostic mode. (Code No. 08)
Replace if defective.
Refer to “CHECKING THE
LEAN ANGLE SENSOR” on
page 9-75.Push the start switch.
Fault code number is not dis-
played
 Service is finished.
Fault code number is dis-
played  Go to item 5.
5 Malfunction in ECU. Replace the ECU.

FUEL INJECTION SYSTEM
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Fault code No.43
Item Fuel system voltage: incorrect voltage supplied to the fuel in-
jector and fuel pump.
Fail-safe system Able to start engine
Able to drive vehicle
Diagnostic code No. 09
Diagnostic tool display Fuel system voltage
Approximately 12.0 (V)
Procedure Disconnect the main relay, and push the start switch or push down
the kickstarter lever.
Item Probable cause of malfunc-
tion and check Maintenance jobConfirmation of service
completion
1 Connection of main relay 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. Start the engine and let it idle
for approximately 5 seconds.
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. Start the engine and let it idle
for approximately 5 seconds.
Fault code number is not dis-
played
 Service is finished.
Fault code number is dis-
played  Go to item 3.
3 Wire harness continuity. Open or short circuit  Re-
place the wire harness.
Between battery terminal and
ECU coupler.
red-red
red-red/white
Between main relay coupler
and ECU coupler.
brown-brown
blue/red-blue/red Start the engine and let it idle
for approximately 5 seconds.
Fault code number is not dis-
played
 Service is finished.
Fault code number is dis-
played  Go to item 4.
4 Defective main relay. No operating sound  Re-
place the main relay. Start the engine and let it idle
for approximately 5 seconds.
Fault code number is not dis-
played
 Service is finished.
Fault code number is dis-
played  Go to item 5.
5 Defective main relay. Execute the diagnostic mode. (Code No. 09)
Fuel system voltage is below
3 V  Replace the main re-
lay. Start the engine and let it idle
for approximately 5 seconds.
Fault code number is not dis-
played
 Service is finished.
Fault code number is dis-
played  Go to item 6.
6 Malfunction in ECU. Replace the ECU.