Yamaha FI Code 43: FI Power Supply — Fix
On Yamaha motorcycles and scooters, FI fault code 43 means the power supply to the injectors and fuel pump is not normal — the FI system isn’t getting correct voltage (often a charging or wiring fault).
- 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 43 with warning light on
- No start or stalling from fuel starvation
- Battery/charging warning signs
How to fix it
- 1
Check battery and charging voltage
1. Test the battery and load. 2. Measure charging voltage at idle and higher RPM against spec. 3. Replace a weak battery or failing regulator/rectifier.
- 2
Inspect grounds and FI wiring
1. Clean and tighten grounds. 2. Check the FI relay and power wiring, then clear the code.
Frequently asked questions
Is code 43 a battery problem?
Often — 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.