E2 on the GOTRAX Fitz16 electric dirt bike means “Throttle malfunction.” Most likely cause: a sticking throttle, a loose throttle plug or a faulty throttle. Try this first: check the throttle snaps back.
The controller is getting a wrong signal from the throttle. A throttle that sticks or doesn't return can make the bike move unexpectedly, so don't ride until it's fixed.
Step-by-step checklist
Work from the top. Steps go from free and easy to shop jobs. Switch the bike off before touching any connector. Tick each step as you go. Your progress is saved on this device.
When it's time for a shop: if you've worked through every step and the problem is still there, contact an authorized dealer for your brand. Bring your notes on when it happens, plus the code.