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:

    Checking the cooling system
    1. Remove: Side covers Upper side cowlings Refer to "GENERAL CHASSIS" on page 4-1. 2. Check: Radiator "1" Radiator inlet hose "2" Radiator outlet hose "3" Coolant reservoir hose "4" Water pump breather hose "5" Cracks/damage → Replace. Refer to "RADIATOR" on page 6-1 ...

    Checking the primary drive gear
    1. Remove: Primary drive gear Refer to "BALANCER GEAR" on page 5-53. 2. Check: Primary drive gear Damage/wear  Replace the primary drive gear and clutch housing as a set. Excessive noise during operation Replace the primary drive gear and clutch housing as a set ...

    Engine tightening torques
    Cylinder head tightening sequence: Generator cover tightening sequence: Clutch cover tightening sequence: Crankcase tightening sequence: A. Left crankcase B. Right crankcase ...

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