Yamaha YZF-R125 Fault Code Guide

Safety First: If the Engine Management Light (EML) is flashing while the engine is running, pull over safely and turn off the bike. A flashing light often indicates a "critical" fault—such as a misfire that could damage the catalytic converter or a sensor failure that could cause the engine to seize.

The YZF-R125 features an on-board diagnostic system. When a fault is detected, the orange engine light will either stay solid or flash in a specific sequence to tell you what's wrong.

How to Read the "Blink" Codes

If you don't have an OBD2 scanner, you can read the flashes on the dashboard:

• Long Flashes (1.5 seconds): These represent the first digit (tens).

• Short Flashes (0.5 seconds): These represent the second digit (units).

• Example: Two long flashes followed by four short flashes = Code 24.

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Common Fault Code Meanings

Code	Component	Common Symptom
12	Crankshaft Position Sensor	Bike won't start; no spark.
13	Intake Air Pressure Sensor	Poor idling; "chugging" under load.
14	Intake Air Pressure (Hose)	Often just a loose or cracked rubber vacuum hose.
15	Throttle Position Sensor (TPS)	Hesitation when twisting the throttle.
21	Coolant Temperature Sensor	Fan stays on constantly or bike runs very "rich."
24	Oxygen (O2) Sensor	Poor fuel economy; surging at constant speeds.
30	Lean Angle Sensor	Bike thinks it has fallen over; cuts ignition.
33	Ignition Coil	Misfiring; bike feels like it's "limping."
41	Lean Angle Sensor (Wiring)	Open or short circuit in the tip-over sensor.
42	Speed Sensor / Neutral Switch	Speedometer stays at 0 or bike stalls when put in gear.
46	Power Supply (Charging System)	Abnormal voltage; usually a failing Stator or Regulator.

Pro Tip: Resetting the Light

On many R125 models, the light will only turn off once the physical fault is fixed and the bike has completed 3 "clean" heat cycles (starting from cold, reaching operating temp, and cooling back down). If the light stays on after a repair, double-check your connector clips!