2016 YAMAHA YZ250F coolant temperature

FUEL INJECTION SYSTEM
8-20
TIP
Make sure that the machine is completely cold before checking the coolant temperature sensor.
Fault code 21
Symptom Coolant temperature sensor: open or short circuit detected.
Fail-safe systemAble to start engine
Able to drive vehicle
Diagnostic code No.06
Diagnostic tool displayDisplays the coolant temperature.
ProcedureCompare the actually measured coolant temperature with the
Yamaha diagnostic tool display value.
Or-
derProbable cause of malfunc-
tion and checkMaintenance job Reinstatement method
1 Connection of coolant tem-
perature 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 Wire harness continuity. Open or short circuit  Re-
place the wire harness.
Between coolant temperature
sensor coupler and ECU cou-
pler.
green/white–green/white
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.
4 Mounted condition of coolant
temperature sensor.
Check for looseness or
pinching.
Check the mounted condition
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.
5 Defective coolant tempera-
ture sensor.Execute the diagnostic mode.
(Code No. 06)
When the machine is cold,
displayed temperature is
close to the ambient temper-
ature.
Improper display  Replace
the coolant temperature sen-
sor.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.
6 Faulty ECU Replace the ECU.

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 (electronic control unit)
7. Intake air pressure sensor
8. Condenser
9. Neutral switch
10.Coolant temperature sensor

ELECTRICAL COMPONENTS
8-44
EAS1SM9341CHECKING THE COOLANT TEMPERATURE
SENSOR
1. Remove:
• Coolant temperature sensor
EWA
WARNING
• Handle the coolant temperature sensor
with special care.
• Never subject the coolant temperature
sensor to strong shocks. If the coolant
temperature sensor is dropped, replace it.
2. Check:
• Coolant temperature sensor resistance
Out of specification  Replace.
▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼
a. Connect the pocket tester ( 1k/100) to
the coolant temperature sensor.
b. Immerse the coolant temperature sensor in
a container filled with coolant.
TIP
Make sure the coolant temperature sensor ter-
minals do not get wet.c. Place a thermometer in the coolant.
d. Slowly heat the coolant, and then let it cool
to the specified temperature indicated in the
table.
e. Check the coolant temperature sensor for
continuity at the temperatures indicated in
the table.
▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲
EAS1SM9342CHECKING THE THROTTLE POSITION
SENSOR
1. Remove:
• Throttle position sensor
(from the throttle body)
EWA
WARNING
• Handle the throttle position sensor with
special care.
• Never subject the throttle position sensor
to strong shocks. If the throttle position
sensor is dropped, replace it. Coolant temperature sensor re-
sistance
2.51–2.78 k at 20 °C (68 °F)
210–221  at 100 °C (212 °F)
Pocket tester
90890-03112
Analog pocket tester
YU-03112-C
• Positive tester probe 
Green/White “1”
• Negative tester probe 
Black/Blue “2”12
G/W B/L
B/L G/W

TROUBLESHOOTING
9-3
Fuel system
1. Throttle body
• Damaged or loose throttle body joint
2. Air filter
• Clogged air filter element
Chassis
1. Brake(s)
• Dragging brake
Electrical system
1. Spark plug
• Incorrect spark plug gap
• Incorrect spark plug heat range
2. Ignition system
• Faulty ECU
• Faulty coolant temperature sensor
EAS1SM9359OVERCOOLING
Cooling system
1. Coolant temperature sensor
• Faulty coolant temperature sensor
EAS1SM9360POOR BRAKING PERFORMANCE
Chassis
1. Brake(s)
• Worn brake pad
• Worn brake disc
• Air in hydraulic brake system
• Leaking brake fluid
• Defective master cylinder kit
• Faulty brake caliper kit
• Faulty brake caliper seal
• Loose union bolt
• Damaged brake hose
• Oil or grease on the brake disc
• Oil or grease on the brake pad
• Incorrect brake fluid level
EAS1SM9361FRONT FORK OIL LEAKING
Chassis
1. Front fork
• Bent, damaged, or rusty inner tube
• Cracked or damaged outer tube
• Improperly installed oil seal
• Damaged oil seal lip
• Incorrect oil level (high)
• Loose damper rod assembly bolt
• Damaged damper rod assembly bolt copper
washer
• Cracked or damaged cap bolt O-ring
EAS1SM9362FAULTY FRONT FORK LEGS
Chassis
1. Front fork
• Bent or damaged inner tube
• Bent or damaged outer tube
• Broken fork spring
• Bent or damaged damper rod
• Incorrect oil viscosity
• Incorrect oil level
EAS1SM9363UNSTABLE HANDLING
Chassis
1. Handlebar
• Bent or improperly installed handlebar
2. Steering head components
• Improperly installed upper bracket
• Improperly installed lower bracket
(improperly tightened ring nut)
• Bent steering stem
• Damaged ball bearing or bearing race
3. Front fork leg (s)
• Uneven oil levels (both front fork legs)
• Unevenly tensioned fork spring (both front
fork legs)
• Broken fork spring
• Bent or damaged inner tube
• Bent or damaged outer tube
4. Swingarm
• Worn bearing or bushing
• Bent or damaged swingarm
5. Rear shock absorber assembly (-ies)
• Faulty rear shock absorber spring
• Leaking oil or gas
6. Tire (s)
• Uneven tire pressures (front and rear)
• Incorrect tire pressure
• Uneven tire wear
7. Wheel (s)
• Incorrect wheel balance
• Broken or loose spoke
• Damaged wheel bearing
• Bent or loose wheel axle
• Excessive wheel runout
8. Frame
• Bent frame
• Damaged steering head pipe
• Improperly installed bearing race

LIST OF SELF-DIAGNOSTIC AND FAIL-SAFE ACTIONS
9-4
EAS1SM9364
LIST OF SELF-DIAGNOSTIC AND FAIL-SAFE ACTIONS
LIST OF DIAGNOSTIC CODES
COMMUNICATION ERROR WITH YAMAHA DIAGNOSTIC TOOLFault
codeITEM Page
12 Crankshaft position sensor: no normal signals are received from the
crankshaft position sensor.8-14
13 Intake air pressure sensor: open or short circuit detected. 8-15
14 Intake air pressure sensor: hose system malfunction (clogged or de-
tached hose)8-16
15 Throttle position sensor: open or short circuit detected. 8-17
16 Throttle position sensor: stuck throttle position sensor is detected. 8-19
21 Coolant temperature sensor: open or short circuit detected. 8-20
22 Intake air temperature sensor: open or short circuit detected. 8-21
30 The vehicle has overturned. 8-22
33 Ignition coil: open or short circuit detected in the primary lead of the
ignition coil.8-23
39 Injector: open or short circuit detected. 8-24
41 ECU: built-in lean angle sensor malfunction 8-25
44 EEPROM fault code No.: an error is detected while reading or writing
on EEPROM.8-26
46 Vehicle system power supply: normal voltage is not supplied to the
ECU.8-27
50 ECU: faulty ECU memory 8-28
Fault
codeITEM Page
Waiting
for con-
nectionNo communication signal is received from the ECU.
8-28
Er-2 Signals from the ECU cannot be received within the specified period
of time.8-29
Er-3 Data from the ECU cannot be received correctly. 8-30
Er-4 Registered data cannot be received from the Yamaha diagnostic tool. 8-31

LIST OF SELF-DIAGNOSTIC AND FAIL-SAFE ACTIONS
9-5
SENSOR OPERATION TABLE
Diag-
nostic
code
No.ITEM Display Procedure
01 Throttle angle
• Fully closed position
• Fully opened positionDisplays the throttle angle.
• 11–14
• 109–116• Check with throttle fully
closed.
• Check with throttle fully
opened.
03 Pressure of suction pipe Displays the intake air pres-
sure.The atmospheric pressure
is displayed on the Yamaha
diagnostic tool.
05 Intake air temperature Displays the intake air tem-
perature.Compare the actually mea-
sured intake air tempera-
ture with the Yamaha
diagnostic tool display val-
ue.
06 Coolant temperature Displays the coolant temper-
ature.Compare the actually mea-
sured coolant temperature
with the Yamaha diagnostic
tool display value.
08 Lean angle sensor
• Upright
•OverturnDisplays the output voltage.
• 1.0 (V)
• 4.0 (V)Remove the ECU, and in-
cline it 45 ° or more.
09 Monitor voltage Displays the voltage of the
external battery connected to
the Yamaha diagnostic tool.
• Approximately 12.0 (V)—
21 Neutral switch
• Gear in neutral
• Gear not in neutral•ON
•OFFOperate the shift pedal.
25 Gear position switch
• Gear in 1st or 2nd
• Gear not in 1st or 2nd•ON
•OFFOperate the shift pedal.
60 EEPROM fault code No.
display
• No fault
• CO adjustment valve
• Power Tuner injection cor-
rection setting 0–8, or
Power Tuner ignition tim-
ing correction setting 0–8•00
•01
•07—
61 Malfunction history ( )
code No. display *1
• There is no history.
• There is some history.•00
• Other: Displays the fault
code of ( ).—

EAS1SM9381
WIRING DIAGRAM
YZ250F/YZ250FG 2016
1. Crankshaft position sensor
2. AC magneto
3. Rectifier/regulator
4. Joint connector
5. Condenser
6. Coupler for connecting option-
al part
7. Engine stop switch
8. Neutral switch
9. ECU (electronic control unit)
10. Ignition coil
11. Spark plug
12. Fuel injector
13. Fuel pump
14. Intake air temperature sensor
15. Coolant temperature sensor
16. Throttle position sensor
17. Intake air pressure sensor
18. Ignition coil sub-lead
EAS1SM9382COLOR CODE
BBlack
Gy Gray
LBlue
Lg Light green
O Orange
PPink
RRed
Sb Sky blue
Y Yellow
B/L Black/Blue
B/R Black/Red
B/W Black/White
B/Y Black/Yellow
Br/W Brown/White
G/W Green/White
L/W Blue/White
P/B Pink/Black
R/B Red/Black
Y/B Yellow/Black
Y/W Yellow/White