YAMAHA YZ250F ELECTRICAL COMPONENTS PARTS

1.	Rectifier/regulator
2.	Intake air pressure sensor
3.	Throttle position sensor
4.	Injector
5.	Mode switch
6.	Intake air temperature sensor
7.	ECU (Engine Control Unit)
8.	Ignition coil
9.	CCU (Communication Control Unit)
10.	Starter relay
11.	Fuse
12.	Battery
13.	Gear position switch
14.	Fuel pump
15.	Coolant temperature sensor

CHECKING THE SWITCHES

1.	Engine stop switch
2.	Mode switch
3.	Gear position switch
4.	Engine start switch

Check each switch for continuity with the digital circuit tester. If the continuity reading is incorrect, check the wiring connections and if necessary, replace the switch.

: Never insert the tester probes into the coupler terminal slots. Always insert the probes from the opposite end “a” of the coupler, taking care not to loosen or damage the leads.

Digital circuit tester (CD732)

90890-03243
Model 88 Multimeter with tachometer

YU-A1927

: When checking for continuity, switch back and forth between the switch positions a few times.

Terminal connections of the switch are shown in the terminal connection diagram below.

The switch positions “a” are shown in the far left column and the switch lead colors are shown in the top row in the switch illustration.

: “” indicates continuity between switch terminals (i.e., a closed circuit at each switch position).

The example illustration below shows that:

There is continuity between red and brown when the switch is “ON”.

CHECKING THE FUSES

The following procedure applies to all of the fuses.

1.Remove:

Seat

Refer to GENERAL CHASSIS.

2.Check:

Fuse “1”

a.Connect the digital circuit tester to the fuse and check the continuity.

: Set the digital circuit tester selector to “Ω”.

Digital circuit tester (CD732)

90890-03243
Model 88 Multimeter with tachometer

YU-A1927

b.If the digital circuit tester indicates “O.L”, replace the fuse.

3.Replace:

Fuse

a.Install a new fuse of the correct amperage rating.

b.Push the start switch to verify if the electrical circuit is operational.

c.If the fuse immediately blows again, check the electrical circuit.

Fuses	Amperage rating	Q’ty
Main	15 A	1
Spare	15 A	1

: Never use a fuse with an amperage rating other than that specified. Improvising or using a fuse with the wrong amperage rating may cause extensive damage to the electrical system, cause the lighting and ignition systems to malfunction and could possibly cause a fire.

4.Install:

Seat

Refer to GENERAL CHASSIS.

CHECKING AND CHARGING THE BATTERY

To avoid sparking, burns, fire, and explosion:

Charge battery only with specified charger.
Use battery only for specified product – no other use.
Do not place near fire or immerse in water.
Do not use battery if it has been dropped, subject to impact, or visibly damaged.
Do not disassemble or modify the battery, or short across its terminals.

To prevent damage to the battery and battery malfunction:

Be sure to charge the battery using only the specified battery charger. Do not use a charger designed for lead-acid batteries. Otherwise, the battery could be damaged, such as from a long period of excessive current or voltage exceeding 16 V.
Avoid excessive current discharge, such as pressing the starter switch for a long time. Wait for more than 10 seconds before attempting to start again. Charge the battery again as soon as possible. A long state of discharge below 10 V will damage the battery.
Do not use the specified battery charger to charge a battery other than the lithium-ion battery. Otherwise, the battery or charger could be damaged.
Be careful not to drop the battery or subject it to strong impacts.
Avoid charging the battery at high temperatures of 65 °C (149 °F) or more or low temperatures under 0 °C (32 °F). A control feature preventing battery charging and discharging will temporarily intervene. The battery will discharge at 65 °C (149 °F) or more or low temperatures under -10 °C (14 °F).
If the battery is charged between 0 °C (32 °F)and 10 °C (50 °F), battery charging may stop halfway without the battery becoming fully charged even when the specified battery charger is used. If this occurs, disconnect the battery charger, and then resume charging again.

: This model uses a lithium-ion battery. When new, the battery is supplied in sleep mode to minimize current discharging until first-time use. In the sleep mode, a voltage as low as approximately 0.1 V can be measured if voltage measurement is performed. As such the battery cannot be used, but this is not a malfunction. By activating the battery as follows, the sleep mode will be canceled and the battery can be used normally.

Charging (activation) steps

1.Remove:

Side cover (left/right)
Seat

Refer to GENERAL CHASSIS.

2.Disconnect:

Battery lead

(from the battery terminals)

: First, disconnect the negative battery lead, and then the positive battery lead.

3.Remove:

Battery

4.Connect the battery charger (special tool) to the battery.

Lithium battery charger

90890-05376
Lithium battery charger

DBY-ACC51-70-02

For instructions on charging and handling the battery charger, refer to the battery charger’s instruction manual.
Once battery charging starts, the sleep mode is canceled.

5.Charge the battery until it is fully charged.

6.Install:

Battery

7.Connect:

Battery lead

(to the battery terminals)

: First, connect the positive battery lead, and then the negative battery lead.

8.Check:

Battery terminal

Dirt → Clean with a wire brush.

Loose connection → Connect properly.

9.Lubricate:

Battery terminal

Recommended lubricant

Dielectric grease

10.Install:

Seat
Side cover (left/right)

Refer to GENERAL CHASSIS.

Checking the battery

: The battery has a limited service life. If the battery cannot be charged or it is determined that the battery cannot be used after checking the battery, it should be replaced. When replacing the battery, be sure to use a Yamaha genuine lithium-ion battery.

: Do not check the battery at high temperature of 65 °C (149 °F) or more or low temperatures below 10 °C (50 °F). Otherwise, the control feature preventing battery charging and discharging will temporarily intervene.

1.Check:

Battery

a.If the battery is hot, wait until the battery has cooled down to the ambient temperature.

b.Measure the voltage between the battery terminals.

13.25 V or more → The battery is normal. Checking is finished.

Less than 13.25 V → Go to step (c).

c.Connect the battery charger (special tool) to the battery and charge it.

Lithium battery charger

90890-05376
Lithium battery charger

DBY-ACC51-70-02

: For instructions on charging and handling the battery charger, refer to the battery charger’s instruction manual.

d.If the battery is hot, wait until the battery has cooled down to the ambient temperature.

e.Measure the voltage between the battery terminals.

13.25 V or more → The battery is normal. Checking is finished.

10 V or more and less than 13.25 V → Perform from step (c) again.

Less than 10 V → Replace the battery.

: Before replacing the battery, make sure that the battery temperature is proper (temperature not more than 65 °C (149 °F) or less than 0 °C (32 °F)). Otherwise, wait until the battery temperature is proper and perform the procedure from step (c) again.

CHECKING THE RELAYS

Check each switch for continuity with the digital circuit tester. If the continuity reading is incorrect, replace the relay.

Digital circuit tester (CD732)

90890-03243
Model 88 Multimeter with tachometer

YU-A1927

1.Disconnect the relay from the wire harness.

2.Connect the digital circuit tester (Ω) and battery (12 V) to the relay terminal as shown.

Check the relay operation.

Out of specification → Replace.

Starter relay

1.	Positive battery terminal
2.	Negative battery terminal
3.	Positive tester probe
4.	Negative tester probe

Result

Continuity

(between “3” to “4”)

Main relay

1.	Positive battery terminal
2.	Negative battery terminal
3.	Positive tester probe
4.	Negative tester probe

Result

Continuity

(between “3” to “4”)

CHECKING THE RELAY UNIT (DIODE)

1.Check:

Diode

Out of specification → Replace.

Digital circuit tester (CD732)

90890-03243
Model 88 Multimeter with tachometer

YU-A1927

: The digital circuit tester and the multimeter with tachometer readings are shown in the following table.

No continuity

Positive tester probe → Blue/Green “1”

Negative tester probe → Blue “2”
Continuity

Positive tester probe → Blue “2”

Negative tester probe → Blue/Green “1”
No continuity

Positive tester probe → Brown/White, Brown “3”

Negative tester probe → Blue/Green, Blue/White “4”
Continuity

Positive tester probe → Blue/Green, Blue/White “4”

Negative tester probe → Brown/White, Brown “3”
No continuity

Positive tester probe → Blue/Black “5”

Negative tester probe → Blue/Red “6”
Continuity

Positive tester probe → Blue/Red “6”

Negative tester probe → Blue/Black “5”

a.Disconnect the diode from the wire harness.

b.Connect the digital circuit tester (Ω) to the diode coupler as shown.

c.Check the diode for continuity.

d.Check the diode for no continuity.

A.	Diode 1
B.	Diode 2
C.	Diode 3

CHECKING THE IGNITION SPARK GAP

1.Check:

Ignition spark gap

Out of specification → Perform the ignition system troubleshooting, starting with step (5).

Refer to TROUBLESHOOTING.

Minimum ignition spark gap

6.0 mm (0.24 in)

: If the ignition spark gap is within specification, the ignition system circuit is operating normally.

a.Remove the spark plug cap from the spark plug.

b.Connect the ignition checker “1” as shown.

Ignition checker

90890-06754
Oppama pet–4000 spark checker

YM-34487

c.Crank the engine, and measure the ignition spark gap “a”.

2.	Spark plug cap

d.Crank the engine, and gradually increase the spark gap until a misfire occurs.

CHECKING THE SPARK PLUG CAP

1.Remove:

Spark plug cap

(from the spark plug lead)

2.Check:

Spark plug cap resistance

Out of specification → Replace.

Resistance

7.50–12.50 kΩ

a.Connect the digital circuit tester (Ω) to the spark plug cap.

Digital circuit tester (CD732)

90890-03243
Model 88 Multimeter with tachometer

YU-A1927

b.Measure the spark plug cap resistance.

CHECKING THE IGNITION COIL

1.Disconnect:

Ignition coil terminal

(from the sub wire harness)
Spark plug cap

(from the ignition coil)

2.Check:

Primary coil resistance

Out of specification → Replace.

Primary coil resistance

2.16–2.64 Ω

a.Connect the digital circuit tester (Ω) to the ignition coil.

Digital circuit tester (CD732)

90890-03243
Model 88 Multimeter with tachometer

YU-A1927

Positive tester probe →

Ignition coil terminal 1 “1”
Negative tester probe →

Ignition coil terminal 2 “2”

b.Measure the primary coil resistance.

3.Check:

Secondary coil resistance

Out of specification → Replace.

Secondary coil resistance

8.64–12.96 kΩ

a.Connect the digital circuit tester (Ω) to the ignition coil.

Digital circuit tester (CD732)

90890-03243
Model 88 Multimeter with tachometer

YU-A1927

Positive tester probe →

Ignition coil terminal 1 “1”
Negative tester probe →

Spark plug lead “2”

b.Measure the secondary coil resistance.

CHECKING THE CRANKSHAFT POSITION SENSOR

1.Disconnect:

Crankshaft position sensor coupler

(from the wire harness)

2.Check:

Crankshaft position sensor resistance

Out of specification → Replace.

Crankshaft position sensor resistance

228–342 Ω

a.Connect the digital circuit tester (Ω) to the crankshaft position sensor coupler.

Digital circuit tester (CD732)

90890-03243
Model 88 Multimeter with tachometer

YU-A1927

Positive tester probe →

Gray “1”
Negative tester probe →

Black “2”

b.Measure the crankshaft position sensor resistance.

CHECKING THE LEAN ANGLE SENSOR

1.Check:

Mounted condition of ECU

Improperly mounted → Remount.

The lean angle sensor is built into the ECU.
The lean angle sensor stops the engine in case of a turnover.
To ensure that the lean angle sensor operates correctly, do not change the installed condition of the ECU.

CHECKING THE STARTER MOTOR OPERATION

1.Check:

Starter motor operation

Does not operate → Perform the electric starting system troubleshooting, starting with step (4).

Refer to TROUBLESHOOTING.

a.Connect the positive battery terminal “1” and starter motor lead “2” with a jumper lead “3”.

A wire that is used as a jumper lead must have at least the same capacity of the battery lead, otherwise the jumper lead may burn.
This check is likely to produce sparks, therefore, make sure no flammable gas or fluid is in the vicinity.

b.Check the starter motor operation.

CHECKING THE STATOR COIL

1.Disconnect:

Stator coil assembly coupler

(from the wire harness)

2.Check:

Stator coil assembly resistance

Out of specification → Replace.

Stator coil resistance

0.512–0.768 Ω

a.Connect the digital circuit tester (Ω) to the stator coil assembly coupler.

Digital circuit tester (CD732)

90890-03243
Model 88 Multimeter with tachometer

YU-A1927

Positive tester probe →

White “1”
Negative tester probe →

White “2”

b.Measure the stator coil assembly resistance.

CHECKING THE RECTIFIER/REGULATOR

1.Check:

Rectifier/regulator output voltage

Out of specification → Replace.

Regulated voltage (DC)

14.0–14.8 V

a.Set the digital tachometer to the ignition coil.

Digital tachometer

90890-06760
Digital tachometer

YU-39951-B

b.Connect the digital circuit tester (DCV) to the rectifier/regulator coupler.

Digital circuit tester (CD732)

90890-03243
Model 88 Multimeter with tachometer

YU-A1927

Positive tester probe →

Red “1”
Negative tester probe →

Black “2”

c.Start the engine and let it run at about 5000 r/min.

d.Measure the output voltage.

CHECKING THE COOLANT TEMPERATURE SENSOR

1.Remove:

Coolant temperature sensor

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.

Coolant temperature sensor resistance

2513–2777 Ω at 20 °C (2513–2777 Ω at 68 °F)
Coolant temperature sensor resistance

210–221 Ω at 100 °C (210–221 Ω at 212 °F)

a.Connect the digital circuit tester (Ω) to the coolant temperature sensor.

Digital circuit tester (CD732)

90890-03243
Model 88 Multimeter with tachometer

YU-A1927

Positive tester probe →

Green/White “1”
Negative tester probe →

Black/Blue “2”

b.Immerse the coolant temperature sensor in a container filled with coolant.

: Make sure the coolant temperature sensor terminals 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.

CHECKING THE THROTTLE POSITION SENSOR INPUT VOLTAGE

1.Check:

Throttle position sensor input voltage

Out of specification → Replace the ECU.

Throttle position sensor input voltage

4–6 V

a.Connect the test harness S– pressure sensor (3P) to the throttle position sensor coupler and the wire harness.

b.Connect the digital circuit tester (DCV) to the test harness S– pressure sensor (3P).

Digital circuit tester (CD732)

90890-03243
Model 88 Multimeter with tachometer

YU-A1927

Test harness S– pressure sensor (3P)

90890-03207
Test harness S– pressure sensor (3P)

YU-03207

Positive tester probe →

Blue “1”
Negative tester probe →

Black/Blue “2”

c.Start the engine.

d.Measure the throttle position sensor input voltage.

CHECKING THE INTAKE AIR TEMPERATURE SENSOR

1.Remove:

Intake air temperature sensor

(from the air filter case)

Handle the intake air temperature sensor with special care.
Never subject the intake air temperature sensor to strong shocks. If the intake air temperature sensor is dropped, replace it.

2.Check:

Intake air temperature sensor resistance

Out of specification → Replace.

Intake air temperature sensor resistance

5400–6600 Ω at 0 °C (5400–6600 Ω at 32 °F)
Intake air temperature sensor resistance

290–390 Ω at 80 °C (290–390 Ω at 176 °F)

a.Connect the digital circuit tester (Ω) to the intake air temperature sensor terminal.

Digital circuit tester (CD732)

90890-03243
Model 88 Multimeter with tachometer

YU-A1927

Positive tester probe →

Brown/White “1”
Negative tester probe →

Black/Blue “2”

CHECKING THE GEAR POSITION SWITCH

1.Remove:

Gear position switch

2.Check:

Gear position switch

Out of specification → Replace.

Digital circuit tester (CD732)

90890-03243
Model 88 Multimeter with tachometer

YU-A1927

Continuity

Positive tester probe →
Sky blue “1”
Negative tester probe →
Sensor terminal “a”
Continuity

Positive tester probe →
Pink “2”
Negative tester probe →
Sensor terminal “b”
Continuity

Positive tester probe →
Pink “2”
Negative tester probe →
Sensor terminal “c”
Continuity

Positive tester probe →
Yellow/White “3”
Negative tester probe →
Sensor terminal “d”
Continuity

Positive tester probe →
Yellow/White “3”
Negative tester probe →
Sensor terminal “e”
Continuity

Positive tester probe →
Yellow/White “3”
Negative tester probe →
Sensor terminal “f”

CHECKING THE INJECTOR

1.Remove:

Fuel injector

Refer to THROTTLE BODY.

2.Check:

Fuel injector resistance

Out of specification → Replace.

Resistance

12.0 Ω

a.Disconnect the fuel injector coupler from the fuel injector.

b.Connect the digital circuit tester (Ω) to the fuel injector coupler.

Digital circuit tester (CD732)

90890-03243
Model 88 Multimeter with tachometer

YU-A1927

Positive tester probe →

Injector terminal “1”
Negative tester probe →

Injector terminal “2”

c.Measure the fuel injector resistance.

CHECKING THE SWITCHES

CHECKING THE FUSES

CHECKING AND CHARGING THE BATTERY

CHECKING THE RELAYS

CHECKING THE RELAY UNIT (DIODE)

CHECKING THE IGNITION SPARK GAP

CHECKING THE SPARK PLUG CAP

CHECKING THE IGNITION COIL

CHECKING THE CRANKSHAFT POSITION SENSOR

CHECKING THE LEAN ANGLE SENSOR

CHECKING THE STARTER MOTOR OPERATION

CHECKING THE STATOR COIL

CHECKING THE RECTIFIER/REGULATOR

CHECKING THE COOLANT TEMPERATURE SENSOR

CHECKING THE THROTTLE POSITION SENSOR INPUT VOLTAGE

CHECKING THE INTAKE AIR TEMPERATURE SENSOR

CHECKING THE GEAR POSITION SWITCH

CHECKING THE INJECTOR

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