Yamaha FI Code 15: Throttle Position Sensor — Causes & Fix
On Yamaha motorcycles and scooters, FI fault code 15 means an open or short circuit was detected in the throttle position sensor (TPS) — the sensor that reports how far the throttle is open.
- Applies to
- Yamaha motorcycles
- Est. repair cost
- $20 – $130
- Time to fix
- 30–90 minutes
What it means
Typical causes are a loose/corroded TPS connector, a worn or misadjusted sensor, or damaged wiring. This is a generic Yamaha fuel-injection (FI) fault code, so it applies across Yamaha FI models — scooters and underbones like the Mio, NMAX, Aerox, and Sniper, plus YZF-R and MT motorcycles. Yamaha shows the code as a number on the diagnostic/odometer display, and the engine-warning light comes on. Once the fault is repaired and the ECU no longer detects it, the code clears; cycling the ignition (or using a Yamaha diagnostic tool) may be needed to confirm.
Symptoms
- FI code 15 with warning light on
- Poor or jerky throttle response, surging
- Stalling or hesitation
How to fix it
- 1
Inspect the TPS connector and wiring
1. Locate the TPS on the throttle body. 2. Reseat the connector; inspect the harness for chafing.
- 2
Check the sensor sweep and replace/adjust
1. Backprobe the signal wire and open the throttle slowly — voltage should rise smoothly. 2. Adjust to spec or replace, then clear the code.
Frequently asked questions
Why does my bike surge with code 15?
A noisy throttle signal makes the ECU constantly re-fuel, which feels like surging. A worn TPS or bad connector is the usual cause.
Last updated July 15, 2026
Guidance only — always consult a qualified professional or the official service manual before carrying out repairs.