Yamaha YZF-R125 Service Manual: Troubleshooting method

The engine operation is not normal and the engine trouble warning light comes on.

1. Check:

  • Fault code number

a. Check the fault code number displayed on the FI diagnostic tool.

b. Identify the faulty system with the fault code.

Refer to "Self-Diagnostic Function table".

c. Identify the probable cause of the malfunction.

Refer to "Diagnostic code table".

2. Check and repair the probable cause of the malfunction.


3. Perform fuel injection system reinstatement action.

Refer to "Reinstatement method" of table in "TROUBLESHOOTING DETAILS" on page 8-41.

4. Set the main switch to "OFF" and back to "ON", and then check that no fault code number is displayed.

NOTE:

If other fault codes are displayed, repeat steps (1) to (4) until no fault code number is displayed.

5. Erase the malfunction history in the diagnostic mode. Refer to "Sensor operation table (Diagnostic code No. 62)".

NOTE:

Setting the main switch to "OFF" will not erase the malfunction history.

The engine operation is not normal but the engine trouble warning light does not come on.

1. Check the operation of the following sensors and actuators in the diagnostic mode. Refer to "Sensor operation table" and "Actuator operation table".


If a malfunction is detected in the sensors or actuators, repair or replace all faulty parts.

If no malfunction is detected in the sensors and actuators, check and repair the inner parts of the engine.

    Self-diagnostic function table
    If the ECU detects an abnormal signal from a sensor while the vehicle is being driven, the ECU illuminates the engine trouble warning light and provides the engine with alternate operating instru ...

    Diagnostic mode
    It is possible to monitor the sensor output data or check the activation of actuators with the FI diagnostic tool connected to the vehicle and set to the normal mode or the diagnostic monitoring ...

    Other materials:

    Separating the crankcase
    1. Remove: Crankcase bolts NOTE: Loosen each bolt 1/4 of a turn at a time, in stages and in the proper sequence as shown. A. Right crankcase B. Left crankcase 2. Turn: Shift drum segment NOTE: Turn the shift drum segment "1" to the position shown in the illustration. In this ...

    Checking the shift drum assembly
    1. Check: Shift drum groove Damage/scratches/wear Replace the shift drum assembly. Shift drum segment "1" Damage/wear  Replace the shift drum assembly. Shift drum bearing "2" Damage/pitting Replace the shift drum assembly. ...

    Installing the generator
    1. Install: Woodruff key Generator rotor Washer Generator rotor nut NOTE: Clean the tapered portion of the crankshaft and the generator rotor hub. When installing the generator rotor, make sure the woodruff key is properly sealed in the keyway of the crankshaft. 2. Tighte ...

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