2015 YAMAHA YZ450F Owners Manual

FUEL INJECTION SYSTEM
8-31
Fault code Er-4
SymptomRegistered data cannot be received from the Yamaha diagnos-
tic tool.
Fail-safe systemAble to start engine
Able to drive vehicle
Diagnostic code No.—
Diagnostic tool display—
Procedure—
Or-
derProbable cause of malfunc-
tion and checkMaintenance job Reinstatement method
1 Connection of Yamaha diag-
nostic tool 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 Wire harness continuity. Open or short circuit  Re-
place the wire harness.
light green–light greenTurn “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 Yamaha diagnostic tool mal-
functionReplace the Yamaha diag-
nostic tool.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.
5 Faulty ECU Replace the ECU.

FUEL PUMP SYSTEM
8-32
EAS1SL5330
FUEL PUMP SYSTEM
EAS1SL5331CIRCUIT DIAGRAM
B/L Gy
BR
A
A
AA
B
RR R R R R R
B
B
B RR
R
Lg
LgB/WB/Y
B/YB
B
BP
PP
Sb
B/LP/B
P/B
YL
YL
L
G/WBr/W
G/WBr/W
B/LB/L
B/L
B/L
B/R
B/R
R/B
R/B
O
OROR
OR
R
R
SbB
GyR
B/W P L B/L
B/L GyB/L B/L B/L B/L B/L LL PP BBBB
PP
Sb
RB
B/RR
R B
B/Y PSb
BB
RR/B
LYB/L
B/W RLg
B/LBr/W
B/L P/B LB/LG/W
BB/Y BB/L B/L B/L B/L B/L B/LBBBBRR
PPPL L LRR RR R
B
OP Gy
R
B/Y Sb
P/B
R/BLgB/RG/WBr/WB/L L Y
RB
B/LGy
R
O
O
R(BLACK) (BLACK)
B/W
4
1
3
2
5
67
8
10
9
1211
13
1415
16
17

FUEL PUMP SYSTEM
8-33
2. AC magneto
3. Rectifier/regulator
4. Joint connector
5. Condenser
7. Engine stop switch
9. ECU
13.Fuel pump

FUEL PUMP SYSTEM
8-34
EAS1SL5332TROUBLESHOOTING
The fuel pump fails to operate.
TIP
Before troubleshooting, remove the following part(s):
1. Seat
2. Side cover (left/right)
3. Air scoop (left/right)
4. Fuel tank
5. Air filter case cover
1. Check the fuel pump system wire
harness connections.NG 
Reconnect.
OK 
2. Check the engine stop switch.
Refer to “CHECKING THE
SWITCHES” on page 8-38.NG 
Replace the engine stop switch.
OK 
3. Check fuel pressure.
Refer to “CHECKING THE FUEL
PRESSURE” on page 7-3.NG 
Replace the fuel pump.
OK 
4. Check the fuel pump system wire
harness.
Refer to “CIRCUIT DIAGRAM” on
page 8-32.NG 
Repair or replace the wire harness.
OK 
Replace the ECU.

FUEL PUMP SYSTEM
8-35

ELECTRICAL COMPONENTS
8-36
EAS1SL5333
ELECTRICAL COMPONENTS
EAS1SL5334
9
10
1
2
3
4
56
7
8

ELECTRICAL COMPONENTS
8-37
1. Rectifier/regulator
2. Intake air pressure sensor
3. Throttle position sensor
4. Injector
5. Intake air temperature sensor
6. ECU
7. Ignition coil
8. Condenser
9. Neutral switch
10.Coolant temperature sensor

ELECTRICAL COMPONENTS
8-38
EAS1SL5335CHECKING THE SWITCHES
B/Y P
Sb
21