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
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    Checking the fuel line
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    Checking the speed sensor
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