2012 YAMAHA YZ450F coolant temperature

4-45
ENGINE REMOVAL
ENGINE REMOVAL
REMOVING THE ELECTRONIC PARTS
Order Part name Q'ty Remarks
Hold the machine by placing the suitable stand
under the frame.Refer to "HANDLING NOTE".
SeatRefer to "SEAT AND SIDE COVERS" sec-
tion.
Fuel tankRefer to "FUEL TANK" section in the CHAP-
TER 6.
Air filter caseRefer to "THROTTLE BODY" section in the
CHAPTER 6.
Radiator Refer to "RADIATOR" section.
1 Rectifier/regulator 1
2 Ignition coil bracket 1
3 Ignition coil 1
4 Atmospheric pressure sensor 1
5 Condenser 1
6 AC magneto lead 1 Disconnect.
7 Coolant temperature sensor coupler 1 Disconnect.

7-1
ELECTRICAL COMPONENTS AND WIRING DIAGRAM
ELECTRICAL
This section is intended for those who have basic knowledge and skill concerning the servicing of Yamaha motorcycles
(e.g., Yamaha dealers, service engineers, etc.) Those who have little knowledge and skill concerning servicing are request-
ed not to undertake inspection, adjustment, disassembly, or reassembly only by reference to this manual. It may lead to
servicing trouble and mechanical damage.
ELECTRICAL COMPONENTS AND WIRING DIAGRAM
ELECTRICAL COMPONENTS
1. Crankshaft position sensor
2. AC magneto
3. Rectifier/regulator
4. Condenser
5. Fuel pump
6. Engine stop switch
7. ECU
8. Ignition coil9. Spark plug
10. Fuel injector
11. Intake air temperature sensor
12. Intake air pressure sensor
13. Throttle position sensor
14. Atmospheric pressure sensor
15. Coolant temperature sensor
16. Coupler for connecting optional part
7

7-2
ELECTRICAL COMPONENTS AND WIRING DIAGRAM
WIRING DIAGRAM
1. Crankshaft position sensor
2. AC magneto
3. Rectifier/regulator
4. Condenser
5. Fuel pump
6. Engine stop switch
7. ECU
8. Ignition coil
9. Spark plug
10. Fuel injector
11. Intake air temperature sensor
12. Intake air pressure sensor
13. Throttle position sensor
14. Atmospheric pressure sensor
15. Coolant temperature sensor
16. Coupler for connecting optional part COLOR CODE
BBlack
Br Brown
Gy Gray
LBlue
Lg Light green
O Orange
PPink
RRed
WWhite
YYellow
B/L Black/Blue
B/R Black/Red
B/W Black/White
B/Y Black/Yellow
Br/W Brown/White
P/W Pink/White
R/B Red/Black
R/W Red/White
STOPON
Gy
Gy
B
B/L
W1
W2
W2 O
R/B
R RR
R
R
R R
Lg
Lg Lg L
P/W
P
YB/RB
B B
BB BB
BB/W
B/W B/W Br/WGyB/L
W1 W1
W2 W2 B/Y
B/Y Br
B/R
R/W
OO
R/B RR
R
L
P/W
PYL
L
LY
Br/WB/L
B/L B/L
B
B/L
B/L
Br
W1
Br/W
W2
R
R O
B/L
L
Y
B/L
Br
R
P
Gy
Gy
B/R
B/R
R/WB/Y
B/L
W1
W2
W1 R
R R
B
B/Y
Lg Lg
O
R/B R/B
Br/W
P/W P/W
LL
Y
B/L B/L
B/L
Br
B
B/W
B/W
B
B
B L
B/L P

7-11
FUEL INJECTION SYSTEM
SENSOR OPERATION TABLE
Diagnos-
tic code
No.ItemActuation or
displayChecking methodActuation or LCD standard display
values
D01 Throttle angle DisplayDisplays the throttle angle. 0–125°
Check with throttle fully closed. When throttle is fully closed:15–19°
Check with throttle fully open. When throttle is fully
opened:95–101 °
D02 Atmosphere DisplayDisplays the atmospheric pres-
sure.
• Measure the atmospheric pres-
sure.0–126 kPa
Displays the atmospheric pressure
according to the elevation and
weather.
Example
0 m above sea level: Approx: 101
kPa
3000 m above sea level:Approx: 70
kPa
D03 Intake air pressure DisplayDisplays the intake air pressure.
• Check the intake manifold pres-
sure.
• Check that the intake air pres-
sure changes while the engine is
being cranked.0–126 kPa
While the engine is stopped: Dis-
plays the atmospheric pressure ac-
cording to the elevation and
weather.
Example
0 m above sea level: Approx: 101
kPa
3000 m above sea level:Approx: 70
kPa
While the engine is being cranked:
Displays the intake air pressure.
D05 Intake air temperature DisplayDisplays the intake air tempera-
ture.
• Check the temperature in the in-
take manifold.-20–100°C
Cold engine: Displayed tempera-
ture is close to the ambient temper-
ature.
Warm engine: Displayed tempera-
ture is approximately 20 °C higher
than the ambient temperature.
D06 Coolant temperature DisplayDisplays the coolant temperature.
• Check the coolant temperature.-20–150°C
Cold engine: Displayed tempera-
ture is close to the ambient temper-
ature.
Warm engine: Displayed tempera-
ture is the current coolant tempera-
ture.
D08 Lean angle sensor DisplayDisplays the lean angle sensor
output voltage.
Remove the ECU and incline it 45°
or more.0–5.0 V
1.0 V: Upright
4.0 V: Overturned
D30 Ignition coil ActuationCheck that power is supplied to
the ignition coil.
• Check that a spark is generated.
• Illuminates the engine trouble
warning light.Actuates the ignition coil for five
times every second.
The "WARNING" LED on the FI di-
agnostic tool comes on each time
the fuel injector is actuated.

7-20
FUEL INJECTION SYSTEM
Make sure that the engine is completely cool before checking the coolant temperature sensor.
Fault code No. 21
Symptom Coolant temperature sensor signal is not received properly.
Fail-safe system Able to start
Able to drive
Diagnostic code No. D06
FI diagnostic tool display -20–150°C
Cold engine: Displayed temperature is close to the ambient temperature.
Warm engine: Displayed temperature is the current coolant temperature.
Checking method Check the coolant temperature.
Item Item/components and probable cause Check or maintenance job Checking method
1 Check the connection and locking condition of
the coolant temperature sensor coupler.
Disconnect the coupler and check the pins
(bent or broken terminals and locking condition
of the pins).Poor connection → Properly con-
nect, repair, or replace.Set the switch on the FI di-
agnostic tool sub-wire har-
ness to "ON", and then
check the fault code dis-
play.
Fault code number is not
displayed → Service is
finished.
Fault code number is dis-
played → Refer to item 2.
2 Check the connection and locking condition of
the wire harness ECU coupler.
Disconnect the coupler and check the pins.
(bent or broken terminals and locking condition
of the pins)Poor connection → Properly con-
nect, repair, or replace.Set the switch on the FI di-
agnostic tool sub-wire har-
ness to "ON", and then
check the fault code dis-
play.
Fault code number is not
displayed → Service is
finished.
Fault code number is dis-
played → Refer to item 3.
3 Continuity of harness Open or short circuit → Replace.
Between coolant temperature sen-
sor coupler and ECU coupler
(Brown–Brown)
(Black/Blue–Black/Blue)Set the switch on the FI di-
agnostic tool sub-wire har-
ness to "ON", and then
check the fault code dis-
play.
Fault code number is not
displayed → Service is
finished.
Fault code number is dis-
played → Refer to item 4.
4 Installed condition of sensor. Check that the sensor is installed
securely and that there are no
pinched leads.Check that the ECU
is installed securely and that there
are no pinched leads.
Incorrect installation → Reinstall
or repair.Set the switch on the FI di-
agnostic tool sub-wire har-
ness to "ON", and then
check the fault code dis-
play.
Fault code number is not
displayed → Service is
finished.
Fault code number is dis-
played → Refer to item 5.

7-21
FUEL INJECTION SYSTEM
Make sure that the engine is completely cool before checking the intake air temperature sensor.
5 Defective coolant temperature sensor. Execute the diagnostic mode (di-
agnostic code No. D06).
Cold engine: Displayed temper-
ature is close to the ambient
temperature.
Displayed value is incorrect → Re-
place. Set the switch on the FI di-
agnostic tool sub-wire har-
ness to "ON", and then
check the fault code dis-
play.
Fault code number is not
displayed → Service is
finished.
Fault code number is dis-
played → Refer to item 6.
6 Malfunction in ECU. Replace the ECU.
Fault code No. 22
Symptom Intake air temperature sensor signal is not received properly.
Fail-safe system Able to start
Able to drive
Diagnostic code No. D05
FI diagnostic tool display -20–100°C
Cold engine: Displayed temperature is close to the ambient temperature.
Warm engine: Displayed temperature is approximately 20°C higher than the ambient tem-
perature.
Checking method Check the temperature in the intake manifold.
Item Item/components and probable cause Check or maintenance job Checking method
1 Check the connection and locking condition of
the intake air temperature sensor coupler.
Disconnect the coupler and check the pins.
(bent or broken terminals and locking condition
of the pins)Poor connection → Properly con-
nect, repair, or replace.Set the switch on the FI di-
agnostic tool sub-wire har-
ness to "ON", and then
check the fault code dis-
play.
Fault code number is not
displayed → Service is
finished.
Fault code number is dis-
played → Refer to item 2. Fault code No. 21
Symptom Coolant temperature sensor signal is not received properly.
Fail-safe system Able to start
Able to drive
Diagnostic code No. D06
FI diagnostic tool display -20–150°C
Cold engine: Displayed temperature is close to the ambient temperature.
Warm engine: Displayed temperature is the current coolant temperature.
Checking method Check the coolant temperature.
Item Item/components and probable cause Check or maintenance job Checking method

7-36
ELECTRICAL COMPONENTS
ELECTRICAL
COMPONENTS
CHECKING THE COOLANT
TEMPERATURE SENSOR
1. Remove:
•Coolant temperature sensor
Refer to "REMOVING THE CYL-
INDER HEAD" section in the
CHAPTER 4.
•Handle the coolant temperature
sensor with special care.
•Never subject the coolant tem-
perature sensor to strong
shocks. If the coolant tempera-
ture sensor is dropped, replace
it.
2. Check:
• Coolant temperature sensor re-
sistance
3. Connect:
•Tester
Tester (+) lead → Brown lead "1"
Tester (-) lead → Black/Blue lead
"2"
4. Immerse the coolant temperature
sensor in a container filled with
coolant.
Make sure the coolant temperature
sensor terminals do not get wet.
5. Place a thermometer "3" in the
coolant.
6. Slowly heat the coolant, and then
let it cool to the specified temper-
ature indicated in the table.Out of specification → Replace.
CHECKING THE INTAKE AIR
PRESSURE SENSOR
1. Check:
• Intake air pressure sensor output
voltage
2. Connect:
• Test harness S–pressure sensor
(3P) "1"
•Tester
Tester (+) lead → Pink/White lead
(wire harness color)
Tester (-) lead → Black/Blue lead
(wire harness color)
3. Connect the FI diagnostic tool
sub-wire harness to a battery, and
then set the switch on the harness
to "ON".
When checking the intake air pres-
sure sensor, do not start the en-
gine.
4. Measure the intake air pressure
sensor output voltage.
Out of specification → ReplaceCHECKING THE INTAKE AIR
TEMPERATURE SENSOR
1. Remove:
• Intake air temperature sensor
(from the air filter case.)
•Handle the intake air temperature
sensor with special care.
•Never subject the intake air tem-
perature sensor to strong
shocks. If the intake air tempera-
ture sensor is dropped, replace
it.
2. Check:
• Intake air temperature sensor re-
sistance
3. Connect:
•Tester
Tester (+) lead → Brown/White
lead "1"
Tester (-) lead →Black/Blue lead
(wire harness color) "2"
Out of specification → Replace.
CHECKING THE ATMOSPHERIC
PRESSURE SENSOR
1. Check:
• Atmospheric pressure sensor out-
put voltage
2. Connect:
• Test harness S- pressure sensor
(3P) "1"
•Tester
Tester (+) lead → Pink lead (wire
harness color)
Tester (-) lead → Black/Blue lead
(wire harness color)
B/L Br
Coolant
tempera-
ture sensor
resistanceTester se-
lector posi-
tion
210–220 Ω
(100°C,
212°F)Ω×100
2.51–2.78
kΩ (20°C,
68°F)kΩ×1
Test harness S–pressure
sensor (3P)
YU-03207/90890-03207
Output volt-
ageTester se-
lector posi-
tion
3.4–3.8 V DCV
Intake air
tempera-
ture sensor
resistanceTester se-
lector posi-
tion
5.4–6.6 kΩ
(0°C, 32°F)kΩ×1
290–390 Ω
(80°C,
176°F)Ω×100
Br/WB/L