2016 YAMAHA YZ450F engine

8-1
EASB111318
TIP
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 knowl-
edge and skill concerning servicing are requested not to undertake inspection, adjustment, disas-
sembly, or reassembly only by reference to this manual. It may lead to servicing trouble and
mechanical damage.

IGNITION SYSTEM
8-3
1. Crankshaft position sensor
2. AC magneto
3. Rectifier/regulator
4. Joint connector
5. Condenser
7. Engine stop switch
8. Neutral switch
9. Launch control switch
10.ECU
11.Ignition coil
12.Spark plug
19.Ignition coil sub-lead

IGNITION SYSTEM
8-4
EASB111321TROUBLESHOOTING
The ignition system fails to operate (no spark or intermittent spark).
TIP
Before troubleshooting, remove the following part(s):
1. Side cover (left/right)
2. Seat
3. Fuel tank
4. Air scoop (left/right)
5. Air filter case cover
1. Check the ignition system wire har-
ness connections.NG 
Reconnect.
OK 
2. Check the spark plug.
Refer to “CHECKING THE SPARK
PLUG” on page 3-37.NG 
Correct or replace the spark plug.
OK 
3. Check the ignition spark gap.
Refer to “CHECKING THE IGNI-
TION SPARK GAP” on page 8-41.OK 
The ignition system circuit is OK.
NG 
4. Check the ignition coil.
Refer to “CHECKING THE IGNI-
TION COIL” on page 8-41.NG 
Replace the ignition coil.
OK 
5. Check the engine stop switch.
Refer to “CHECKING THE
SWITCHES” on page 8-38.NG 
Replace the engine stop switch.
OK 
6. Check the crankshaft position sen-
sor.
Refer to “CHECKING THE CRANK-
SHAFT POSITION SENSOR” on
page 8-42.NG 
Replace the crankshaft position sensor.
OK 
7. Check the stator coil.
Refer to “CHECKING THE STA-
TOR COIL” on page 8-42.NG 
Replace the stator coil.
OK 

FUEL INJECTION SYSTEM
8-11
1. Crankshaft position sensor
2. AC magneto
3. Rectifier/regulator
4. Joint connector
5. Condenser
7. Engine stop switch
8. Neutral switch
10.ECU
13.Fuel injector
14.Fuel pump
15.Intake air temperature sensor
16.Coolant temperature sensor
17.Throttle position sensor
18.Intake air temperature sensor

FUEL INJECTION SYSTEM
8-13
CONNECTING THE YAMAHA DIAGNOSTIC TOOL
1. Remove the coupler for connecting setting tool.
2. Connect the FI diagnostic tool sub-lead.
3. Connect the FI diagnostic tool sub-lead to the battery.
TIP
• Prepare the fully charged 12 V battery for yourself.
• For information on how to connect and use the Yamaha diagnostic tool, refer to “YAMAHA DIGNO-
STIC TOOL OPERATION MANUAL”.
EASB111327TROUBLESHOOTING DETAILS
This section describes the measures per fault code No. displayed on the Yamaha diagnostic tool.
Check and service the items or components that are the probable cause of the malfunction following
the order given in the troubleshooting chart.
After the check and service of the malfunctioning part have been completed, reset the Yamaha diag-
nostic tool display according to the “Reinstatement method”.
Fault code No.: To be displayed on the Yamaha diagnostic tool when the engine fails to work nor-
mally
Diagnostic code No.: To be used when the diagnostic mode is active FI diagnostic tool sub-lead
90890-03212
YU-03212
1. Vehicle
2. Coupler for connecting optional part
3. FI diagnostic tool sub-lead
4. Sub-harness (included with the Yamaha di-
agnostic tool)
5. Vehicle communication cable (included with
the Yamaha diagnostic tool)
6. Yamaha diagnostic tool
7. Battery (12 V)
1
3 2
2456
7

FUEL INJECTION SYSTEM
8-14
Fault code 12
SymptomCrankshaft position sensor: no normal signals are received
from the crankshaft position sensor.
Fail-safe systemUnable to start engine
Unable to drive vehicle
Diagnostic code No.—
Diagnostic tool display—
Procedure—
Or-
derProbable cause of malfunc-
tion and checkMaintenance job Reinstatement method
1 Connection of crankshaft po-
sition sensor coupler.
Check the locking condition
of the coupler.
Disconnect the coupler, and
check the pins (for bent or
broken terminals and locking
condition of the pins).Improperly connected 
Connect the coupler secure-
ly, or repair/replace the wire
harness.Crank the engine.
Fault code No. is not dis-
played  Repair is finished.
Fault code No. is displayed 
Go to next order.
2 Connection of wire harness
ECU coupler.
Check the locking condition
of the coupler.
Disconnect the coupler, and
check the pins (for bent or
broken terminals and locking
condition of the pins).Improperly connected 
Connect the coupler secure-
ly, or repair/replace the wire
harness.Crank the engine.
Fault code No. is not dis-
played  Repair is finished.
Fault code No. is displayed 
Go to next order.
3 Wire harness continuity. Open or short circuit  Re-
place the wire harness.
Between the crankshaft posi-
tion sensor coupler and ECU
coupler.
gray–gray
black/blue–black/blueCrank the engine.
Fault code No. is not dis-
played  Repair is finished.
Fault code No. is displayed 
Go to next order.
4 Mounted condition of crank-
shaft position sensor.
Check for looseness or
pinching.
Check the gap between the
crankshaft position sensor
and the pickup rotor.Improperly mounted sensor
 Remount or replace the
sensor. “AC MAGNETO” on
page 5-61.Crank the engine.
Fault code No. is not dis-
played  Repair is finished.
Fault code No. is displayed 
Go to next order.
5 Defective crankshaft position
sensor.Check the crankshaft position
sensor.
“CHECKING THE CRANK-
SHAFT POSITION SEN-
SOR” on page 8-42.Crank the engine.
Fault code No. is not dis-
played  Repair is finished.
Fault code No. is displayed 
Go to next order.
6 Faulty ECU Replace the ECU.

FUEL INJECTION SYSTEM
8-15
TIP
If fault code Nos. 13 and 14 are both displayed, perform checkup and repair jobs for fault code No.
13 first.
Fault code 13
Symptom Intake air pressure sensor: open or short circuit detected.
Fail-safe systemAble to start engine
Able to drive vehicle
Diagnostic code No.03
Diagnostic tool displayDisplays the intake air pressure.
ProcedureThe atmospheric pressure is displayed on the Yamaha diagnostic
tool.
Or-
derProbable cause of malfunc-
tion and checkMaintenance job Reinstatement method
1 Connection of intake air pres-
sure sensor coupler.
Check the locking condition
of the coupler.
Disconnect the coupler, and
check the pins (for bent or
broken terminals and locking
condition of the pins).Improperly connected 
Connect the coupler secure-
ly, or repair/replace the wire
harness.Turn “ON” the switch on the
FI diagnostic tool sub-lead.
Fault code No. is not dis-
played  Repair is finished.
Fault code No. is displayed 
Go to next order.
2 Connection of wire harness
ECU coupler.
Check the locking condition
of the coupler.
Disconnect the coupler, and
check the pins (for bent or
broken terminals and locking
condition of the pins).Improperly connected 
Connect the coupler secure-
ly, or repair/replace the wire
harness.Turn “ON” the switch on the
FI diagnostic tool sub-lead.
Fault code No. is not dis-
played  Repair is finished.
Fault code No. is displayed 
Go to next order.
3 Connection of sub wire har-
ness coupler.
Check the locking condition
of the coupler.
Disconnect the coupler, and
check the pins (for bent or
broken terminals and locking
condition of the pins).Improperly connected 
Connect the coupler secure-
ly, or repair/replace the sub-
wire harness.Turn “ON” the switch on the
FI diagnostic tool sub-lead.
Fault code No. is not dis-
played  Repair is finished.
Fault code No. is displayed 
Go to next order.
4 Wire harness continuity. Open or short circuit  Re-
place the wire harness.
Between intake air pressure
sensor coupler and ECU cou-
pler.
pink/black–pink/black
blue–blue
black/blue–black/blueTurn “ON” the switch on the
FI diagnostic tool sub-lead.
Fault code No. is not dis-
played  Repair is finished.
Fault code No. is displayed 
Go to next order.
5 Mounted condition of intake
air pressure sensor.
Check for looseness or
pinching.
Check the mounted position
for correctness.Improperly mounted sensor
 Remount or replace the
sensor.Turn “ON” the switch on the
FI diagnostic tool sub-lead.
Fault code No. is not dis-
played  Repair is finished.
Fault code No. is displayed 
Go to next order.

FUEL INJECTION SYSTEM
8-16
TIP
If fault code Nos. 13 and 14 are both displayed, perform checkup and repair jobs for fault code No.
13 first.6 Defective intake air pressure
sensor.Execute the diagnostic mode.
(Code No.03)
Atmospheric pressure at the
current altitude and weather
conditions is indicated.
0 m above sea level: About
101 kPa
1000 m above sea level:
About 90 kPa
2000 m above sea level:
About 80 kPa
3000 m above sea level:
About 70 kPaTurn “ON” the switch on the
FI diagnostic tool sub-lead.
Fault code No. is not dis-
played  Repair is finished.
Fault code No. is displayed 
Go to next order.
7 Faulty ECU Replace the ECU.
Fault code 14
SymptomIntake air pressure sensor: hose system malfunction (clogged
or detached hose)
Fail-safe systemAble to start engine
Able to drive vehicle
Diagnostic code No.03
Diagnostic tool displayDisplays the intake air pressure.
ProcedureThe atmospheric pressure is displayed on the Yamaha diagnostic
tool.
Or-
derProbable cause of malfunc-
tion and checkMaintenance job Reinstatement method
1 The intake air pressure sen-
sor hose is damaged, discon-
nected, clogged, twisted or
bent.Repair or replace the sensor
hose.After starting the engine, idle
this and wait about 5 sec-
onds.
Fault code No. is not dis-
played  Repair is finished.
Fault code No. is displayed 
Go to next order. Fault code 13
Symptom Intake air pressure sensor: open or short circuit detected.