2012 YAMAHA YZ450F check engine

7-4
IGNITION SYSTEM
SPARK GAP TEST
1. Disconnect the spark plug cap
from spark plug.
2. Connect the dynamic spark tester
"1" (ignition checker "2") as
shown.
• Spark plug cap "3"
• Spark plug "4"
A. For USA and CDN
B. Except for USA and CDN
3. Kick the kickstarter crank.
4. Check the ignition spark gap.
5. Start engine, and increase spark
gap until misfire occurs. (for USA
and CDN only)
6. Inspect:
• Sealed portion of spark plug cap
"a"
• Spark plug terminal pin "b"
• Threaded portion of spark plug "c"
7. Inspect:
• Installed condition of spark plug
and spark plug cap
Push in the spark plug cap, mak-
ing sure that it is securely fitted
into the hole in the cylinder head
cover.CHECKING THE COUPLERS AND
LEADS CONNECTION
1. Check:
• Couplers and leads connection
Rust/dust/looseness/short-circuit
→Repair or replace.
CHECKING THE ENGINE STOP
SWITCH
1. Inspect:
• Engine stop switch conduction
Not conductive while it is pushed→
Replace.
Conductive while it is freed→Re-
place.
Set the tester selection position to "Ω
× 1".
CHECKING THE IGNITION COIL
1. Remove the ignition coil cap.
2. Inspect:
• Primary coil resistance
Out of specification→Replace.3. Inspect:
• Secondary coil resistance
Out of specification→Replace.
Disconnect the spark plug cap before
measuring the secondary coil resis-
tance.
CHECKING THE AC MAGNETO
1. Inspect:
• Crankshaft position sensor resis-
tance
Out of specification→Replace.
Minimum spark gap:
6.0 mm (0.24 in)
Tester (+) lead→Black lead "1"
Tester (-) lead→Black lead "2"
Result
Conductive (while the
engine stop switch is
pushed)
Tester (+) lead→Orange lead "1"
Tester (-) lead→Red lead "2"
Primary
coil resis-
tanceTester se-
lector posi-
tion
3.57–4.83
Ω at 20°C
(68°F) Ω × 1
BB
Tester (+) lead→Orange lead "1"
Tester (-) lead→Spark plug termi-
nal "2"
Secondary
coil resis-
tanceTester se-
lector posi-
tion
10.71–14.49
kΩ at 20°C
(68°F) kΩ × 1
Tester (+) lead→Gray lead "1"
Tester (-) lead→Black lead "2"
Crankshaft
position
sensor re-
sistanceTester se-
lector posi-
tion
248–372 Ω
at 20°C
(68°F)Ω × 100
GyB

7-7
THROTTLE POSITION SENSOR SYSTEM
HANDLING NOTE
Do not loosen the screw (throttle
position sensor) "1" except when
changing the throttle position sen-
sor due to failure because it will
cause a drop in engine perfor-
mance.
CHECKING THE COUPLERS AND
LEADS CONNECTION
1. Check:
• Couplers and leads connection
Rust/dust/looseness/short-circuit
→Repair or replace.
CHECKING THE THROTTLE
POSITION SENSOR
1. Inspect:
• Throttle position sensor resis-
tance
Out of specification→Replace.2. Inspect:
• Throttle position sensor variable
resistance
Check that the resistance in in-
creased as the throttle grip is
moved from the full close position
to the full open position.
Out of specification→Replace.
CHANGING AND ADJUSTING THE
THROTTLE POSITION SENSOR
1. Remove:
• Throttle position sensor coupler
2. Remove:
• Screw (throttle position sensor)
"1"
• Throttle position sensor "2"
Loosen the screw (throttle position
sensor) using the T25 bit.
3. Replace:
• Throttle position sensor
4. Install:
• Throttle position sensor "1"
• Screw (throttle position sensor)
"2"
• Align the projection "b" on the throt-
tle body with the slot "a" in the throt-
tle position sensor.
• Temporarily tighten the screw
(throttle position sensor).
5. Make sure that the throttle grip is
in the fully closed position.
6. Install:
• Throttle position sensor coupler
7. Connect the FI diagnostic tool.
(Refer to "CONNECTING THE FI
DIAGNOSTIC TOOL".)
8. Set the FI diagnostic tool to the di-
agnostic mode, and then select
diagnostic code No. D01. (Refer
to "SETTING THE DIAGNOSTIC
MODE".)
9. Adjust the position of the throttle
position sensor so that the angle
displayed on the LCD of the FI di-
agnostic tool is 12–21°.
10. After adjusting the throttle posi-
tion sensor angle, tighten the
throttle position sensor screw "1".
Tighten the screw (throttle position
sensor) using the T25 bit.
Tester (+) lead→Blue lead "1"
Tester (-) lead→Black lead "2"
Throttle po-
sition sen-
sor coil
resistanceTester se-
lector posi-
tion
4–6 kΩ at
20°C (68 °F) kΩ×1
Y
B L
Tester (+) lead→Yellow lead "1"
Tester (-) lead→Black lead "2"
Throttle position
sensor coil vari-
able resistanceTester
selec-
tor po-
sition
Full
closedFull
opened
kΩ×1 Zero
–2
kΩat
20°C
(68°F)4–6
kΩat
20°C
(68°F)
Y
B L
Screw (throttle position
sensor)
3 Nm (0.3 m•kg, 2.2
ft•lb)

7-8
THROTTLE POSITION SENSOR SYSTEM
CHECKING THE THROTTLE
POSITION SENSOR INPUT
VOLTAGE
1. Disconnect the throttle position
sensor coupler.
2. Connect the test harness-speed
sensor (3P) "1" as shown.
3. Start the engine.
4. Inspect:
• Throttle position sensor input volt-
age
Out of specification → Replace
the ECU.Test harness-speed sen-
sor (3P)
YU-03208/90890-03208
Tester (+) lead→Blue lead (wire
harness color)
Tester (-) lead→Black/Blue lead
(wire harness color)
Throttle po-
sition sen-
sor input
voltage Tester se-
lector posi-
tion
4–6 V DCV-20

7-9
FUEL INJECTION SYSTEM
FUEL INJECTION SYSTEM
TROUBLESHOOTING METHOD
Engine starting problems, engine
idling speed problems, and medium
and high-speed performance prob-
lems
1. CHECK:
• Refer to "TROUBLESHOOTING"
section in the chapter 3.
2. Connect the FI diagnostic tool.
(Refer to "CONNECTING THE FI
DIAGNOSTIC TOOL".)
3. Check the fault code number.
(Refer to "TROUBLESHOOTING
DETAILS".)
• Check the fault code number that is
displayed on the LCD of the FI diag-
nostic tool.
• Identify the system with the mal-
function.(Refer to "TROUBLE-
SHOOTING DETAILS".)
4. Checking and repair the probable
case of malfunction.
• Fault code No. YES.
Check and repair.
Refer to "TROUBLESHOOTING
DETAILS".
Refer to "SENSOR OPERATION
TABLE".
• Fault code No. NO.
Check each sensor and actuator
in the diagnostic mode.
Refer to "SETTING THE DIAG-
NOSTIC MODE".
Refer to "SENSOR OPERATION
TABLE".
If the sensors or actuators are
damaged, check and, if neces-
sary, repair or replace all faulty
parts.
If the sensors or actuators are not
damaged, check and, if neces-
sary, repair or replace the engine
inner parts.5. Perform ECU reinstatement ac-
tion.
Refer to "Reinstatement method"
of table in "TROUBLESHOOTING
DETAILS".
6. Set the switch on the FI diagnostic
tool sub-wire harness from "OFF"
to "ON", and then check whether
a fault code number is displayed
again.
If other fault code displayed, repeat
steps (2) to (5) until all fault code
number is not displayed.
7. Set the switch on the FI diagnostic
tool sub-wire harness to "OFF",
and then disconnect the FI diag-
nostic tool, FI diagnostic tool sub-
wire harness, and battery. Place
the accessory coupler in its origi-
nal position.
The malfunction history is stored
even if the switch on the FI diagnostic
tool sub-wire harness is set to "OFF".
Erase the malfunction history in the
diagnostic mode. (Refer to "DIAG-
NOSTIC CODE TABLE (Diagnostic
code No. D62)".)
CONNECTING THE FI
DIAGNOSTIC TOOL
1. Connect the following items to the
accessory coupler as shown.
• FI diagnostic tool "1"
• FI diagnostic tool sub-wire har-
ness "2"
• Battery "3"
• Because this vehicle is not
equipped with a battery, a 12 V
battery is required to use the FI di-
agnostic tool.
• Make sure that the switch on the
FI diagnostic tool sub-wire har-
ness is set to "OFF".
• The "POWER" LED (green)
comes on.
CHECKING THE FAULT CODES
1. Set the switch on the FI diagnostic
tool subwire harness to "ON".
When the switch on the FI diagnostic
tool sub-wire harness is set to "ON",
make sure that "Waiting for connec-
tion" is displayed on the LCD of the FI
diagnostic tool.
2. Check:
• Fault code number
• If a malfunction is detected in the
system, the fault code appears on
the LCD of the FI diagnostic tool
and the "WARNING" LED (orange)
comes on.
• To start the engine, set the switch
on the FI diagnostic tool sub-wire
harness to "OFF".
• When the engine is running, fault
code numbers will not be displayed
on the LCD of the FI diagnostic tool
even if a malfunction is detected in
the system. The "WARNING" LED
(orange) comes on.
3. Set the switch on the FI diagnostic
tool subwire harness to "OFF". FI diagnostic tool
YU-03182/90890-03182
FI diagnostic tool sub-
wire harness
YU-03212/90890-03212
2100 60
60

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.

7-13
FUEL INJECTION SYSTEM
TROUBLESHOOTING DETAILS
This section describes the countermeasures per fault code number displayed on the FI diagnostic tool. Check and service
the items or components that are the probable cause of the malfunction following the order given. After the check and ser-
vice of the malfunctioning part have been completed, reset the FI diagnostic tool display according to the "Reinstatement
method".
Fault code No.
Fault code number displayed on the FI diagnostic tool when the engine failed to work normally. Refer to "FAULT CODE
TABLE".
Diagnostic code No.
Diagnostic code number to be used when the diagnostic mode is operated. Refer to "DIAGNOSTIC CODE TABLE".
Fault code No. 12
Symptom No normal signals are received from the crankshaft position sensor.
Fail-safe system Able to start
Able to drive
Diagnostic code No. —
FI diagnostic tool display —
Checking method —
Item Item/components and probable cause Check or maintenance job Checking method
1 Check the connection and locking condition of
the crankshaft position 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.Crank the engine and
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.Crank the engine and
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 the crankshaft position
sensor coupler and ECU coupler.
(Gray–Gray)
(Black/Blue–Black/Blue)Crank the engine and
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 gap between the crankshaft po-
sition sensor and the rotor is 0.85 mm.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.Crank the engine and
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.

7-14
FUEL INJECTION SYSTEM
If fault code Nos. 13 and 14 are both displayed, perform the checks and maintenance jobs for fault code No. 13 first.
5 Defective crankshaft position sensor. Sensor malfunction → Replace.
Refer to "CHECKING THE AC
MAGNETO" section.Crank the engine and
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. 13
Symptom Intake air pressure sensor signal is not received properly.
Fail-safe system Able to start
Able to drive
Diagnostic code No. D03
FI diagnostic tool display Intake air pressure
Checking method Crank the engine. (If the display value changes, the performance is OK.)
Item Item/components and probable cause Check or maintenance job Checking method
1 Check the connection and locking condition of
the intake air pressure 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. Fault code No. 12
Symptom No normal signals are received from the crankshaft position sensor.
Fail-safe system Able to start
Able to drive
Diagnostic code No. —
FI diagnostic tool display —
Checking method —
Item Item/components and probable cause Check or maintenance job Checking method

7-15
FUEL INJECTION SYSTEM
3 Continuity of harness Open or short circuit → Replace.
Between the intake air pressure
sensor coupler and ECU coupler.
(Black/Blue–Black/Blue)
(Pink/White–Pink/White)
(Blue–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.
Make sure that the installation position is cor-
rect.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.
Incorrect installation position →
Properly install.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.
5 Defective intake air pressure sensor. Execute the diagnostic mode (di-
agnostic code No. D03).
When the engine is stopped,
displays the atmospheric pres-
sure according to the elevation
and weather.
0 m above sea level: Approx.
101 kPa
1000 m above sea level: Ap-
prox. 90 kPa
2000 m above sea level: Ap-
prox. 80 kPa
3000 m above sea level: Ap-
prox. 70 kPa
Check that the value changes
while the engine is being
cranked.
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. 13
Symptom Intake air pressure sensor signal is not received properly.
Fail-safe system Able to start
Able to drive
Diagnostic code No. D03
FI diagnostic tool display Intake air pressure
Checking method Crank the engine. (If the display value changes, the performance is OK.)
Item Item/components and probable cause Check or maintenance job Checking method