YAMAHA YZ250F 2016 Owners Manual

IGNITION SYSTEM
8-5
8. Check the ignition system wire har-
ness.
Refer to “CIRCUIT DIAGRAM” on
page 8-2.NG 
Repair or replace the wire harness.
OK 
Replace the ECU.

CHARGING SYSTEM
8-6
EAS27200
CHARGING SYSTEM
EAS1SM9322CIRCUIT DIAGRAM
ONOFF
R O
OR
RRRRRRR
BBBBB
LLLB/LB/LB/LB/LB/LB/L
B/L
Gy
W
W
W
W
R
R
B
B
B
Y/B
Y/B
Y/W
Y/WB/YL/WB/R
B/Y
B/Y
B/W
R/B
R/B
B/R
B/R
G/WP/B
P/B
B/L
B/L
B/L
G/W
Br/W
Br/W
B/LB/L
B/W
SbP
Sb
Sb
P
P
P
L
L
LY
Y
B
B
LgGy
Lg
R
R
R
R
R
R
R
O
O
O
O
WWW W
W W
W WR B
B/LGyB Gy
BRRB
RLgB/W
B R
B/YB
B B
PY/BSbSbY/WP
BGy R
B/WB/LLYP/BG/WB/R
R/BLg
Br/W
P
O
B/YY/BSb
RR/B
RB/R
B/LBr/WB/L G/W
LYB/L
B/LP/BL
LLLRRRRRRR
BBB BB
B/L B/L B/L B/L B/L B/L

CHARGING SYSTEM
8-7
2. AC magneto
3. Rectifier/regulator
4. Joint connector
5. Condenser

CHARGING SYSTEM
8-8
EAS1SM9323TROUBLESHOOTING
The condenser is not being charged.
TIP
Before troubleshooting, remove the following part (s):
1. Seat
2. Air scoop (left)
1. Check the entire charging system’s
wiring.NG 
Reconnect.
OK 
2. Check the rectifier/regulator.
Refer to “CHECKING THE RECTI-
FIER/REGULATOR” on page 8-43.NG 
Replace the rectifier/regulator.
OK 
3. Check the stator coil.
Refer to “CHECKING THE STA-
TOR COIL” on page 8-43.NG 
Replace the stator coil.
OK 
4. Check the charging system wire
harness.
Refer to “CIRCUIT DIAGRAM” on
page 8-6.NG 
Repair or replace the wire harness.
OK 
Replace the condenser.

CHARGING SYSTEM
8-9

FUEL INJECTION SYSTEM
8-10
EAS1SM9324
FUEL INJECTION SYSTEM
EAS1SM9325CIRCUIT DIAGRAM
ONOFF
R O
OR
RRRRRRR
BBBBB
LLLB/LB/LB/LB/LB/LB/L
B/L
Gy
W
W
W
W
R
R
B
B
B
Y/B
Y/B
Y/W
Y/WB/YL/WB/R
B/Y
B/Y
B/W
R/B
R/B
B/R
B/R
G/WP/B
P/B
B/L
B/L
B/L
G/W
Br/W
Br/W
B/LB/L
B/W
SbP
Sb
Sb
P
P
P
L
L
LY
Y
B
B
LgGy
Lg
R
R
R
R
R
R
R
O
O
O
O
WWW W
W W
W WR B
B/LGyB Gy
BRRB
RLgB/W
B R
B/YB
B B
PY/BSbSbY/WP
BGy R
B/WB/LLYP/BG/WB/R
R/BLg
Br/W
P
O
B/YY/BSb
RR/B
RB/R
B/LBr/WB/L G/W
LYB/L
B/LP/BL
LLLRRRRRRR
BBB BB
B/L B/L B/L B/L B/L B/L

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
9. ECU (electronic control unit)
12.Fuel injector
13.Fuel pump
14.Intake air temperature sensor
15.Coolant temperature sensor
16.Throttle position sensor
17.Intake air temperature sensor

FUEL INJECTION SYSTEM
8-12
EAS1SM9326YAMAHA DIAGNOSTIC TOOL
This model uses the Yamaha diagnostic tool to identify malfunctions.
For information about using the Yamaha diagnostic tool, refer to the operation manual that is included
with the tool.
FEATURES OF THE YAMAHA DIAGNOSTIC TOOL
A diagnosis can be made more quickly than traditional methods with the Yamaha diagnostic tool.
Using this software, ECU and sensor data, as well as fault diagnosis, vehicle maintenance, and any
necessary information can be recorded and displayed on your computer screen through a USB
adapter connected to the computer interface with a communication cable connected to the vehicle’s
ECU.
Data obtained in various functions can be saved as vehicle history, and can be accumulated.
FUNCTIONS OF THE YAMAHA DIAGNOSTIC TOOL
However, the diagnostic tool cannot be used to freely change the basic vehicle functions, such as
adjusting the ignition timing.
CONNECTING THE YAMAHA DIAGNOSTIC TOOL
1. Remove the coupler for connecting setting tool.Yamaha diagnostic tool
90890-03231
Yamaha diagnostic tool (US)
90890-03234
Fault diagnosis mode Fault codes recorded on the ECU are read, and the con-
tents are displayed.
Function diagnostic mode Check the operation of the output value of each sensor
and actuator.
Inspection mode Determine whether each sensor or actuator is functioning
properly.
CO adjustment mode Adjust the concentration of CO admissions during idling.
Monitoring mode Displays a graph of sensor output values for actual oper-
ating conditions.
Logging mode Records and saves the sensor output value in actual driv-
ing conditions.
View log Displays the logging data.
ECU rewrite If necessary, the ECU is rewritten using the ECU rewrite
data provided by Yamaha. Ignition timing adjustment, etc.
cannot be changed from the vehicle’s original state.

FUEL INJECTION SYSTEM
8-13
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”.
EAS1SM9327TROUBLESHOOTING 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 5-58.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.