Yamaha YZF-R125 Service Manual: Throttle position sensor

1. Check:

  • Throttle position sensor

a. Connect the digital circuit tester to the terminals of the throttle body sensor assembly coupler as shown.


  • Positive tester probe → gray/red terminal "1"
  • Negative tester probe → gray/black terminal "2"

b. Measure the throttle position sensor input voltage.

Out of specification → Replace or repair the wire harness.


c. Connect the digital circuit tester to the terminals of the throttle body sensor assembly coupler as shown.

  • Positive tester probe → yellow terminal "3"
  • Negative tester probe → gray/black terminal "2"

d. While slowly opening the throttle, check that the throttle position sensor output voltage is increased.

Voltage does not change or it changes abruptly → Replace the throttle body.

Out of specification (closed position) → Replace the throttle body.


Throttle position sensor


    Checking the throttle body sensor assembly
    WARNING Do not remove the throttle body sensor assembly. Handle the throttle body sensor assembly with special care Never subject the throttle body sensor assembly to strong ...

    Intake air pressure sensor
    1. Check: Intake air pressure sensor output voltage Out of specification Replace the throttle body. a. Connect the pocket tester (DC 20 V) to the throttle body sensor assembly coupler as ...

    Other materials:

    Removing the throttle body
    1. Extract the fuel in the fuel tank through the fuel tank filler hole with a pump. 2. Disconnect: Fuel hose WARNINGCover the fuel hose connections with a cloth when disconnecting them. Residual pressure in the fuel lines could cause fuel to spurt out when removing the h ...

    Removing the front fork legs
    The following procedure applies to both of the front fork legs. 1. Stand the vehicle on a level surface. WARNINGSecurely support the vehicle so that there is no danger of it falling over. 2. Loosen: Handlebar pinch bolt "1" Handlebar bolt "2" Upper bracket ...

    Removing the rear brake caliper
    NOTE: Before disassembling the brake caliper, drain the brake fluid from the entire brake system. 1. Remove: Union bolt "1" Copper washers "2" Brake hose "3" NOTE: Put the end of the brake hose into a container and pump out the brake fluid carefully. ...

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