Yamaha FI Code 46: FI Power Supply — Causes & Fix
On Yamaha motorcycles and scooters, FI fault code 46 means a power-supply fault to the fuel-injection system was detected — the FI system isn’t getting correct voltage (often a charging or wiring problem).
- Applies to
- Yamaha motorcycles
- Est. repair cost
- $30 – $250
- Time to fix
- 30–90 minutes
What it means
Common causes are a weak battery, a failing charging system (stator/regulator-rectifier), corroded grounds, or damaged FI power wiring/relay. 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 46 with warning light on
- Weak or erratic running, stalling
- Battery/charging warning signs
How to fix it
- 1
Check battery and charging voltage
1. Test battery voltage and load. 2. Measure charging voltage at idle and higher RPM — it should be within the charging spec. 3. Replace a weak battery or failing regulator/rectifier.
- 2
Inspect grounds and FI power wiring
1. Clean and tighten ground connections. 2. Check the FI relay and power wiring for corrosion or breaks, then clear the code.
Frequently asked questions
Is code 46 a battery problem?
Often, yes — a weak battery or failing charging system starves the FI system of steady voltage. Test charging before replacing FI parts.
Last updated July 15, 2026
Guidance only — always consult a qualified professional or the official service manual before carrying out repairs.