S866 code list · S866 Display

E04 Error on S866 Display

What it means + how to fix it Commonly reported

Quick answer

E04 on the S866 means “6 km/h push (walk) mode.” This is a normal mode, not a fault. To clear it: let go of the walk-assist button.

Try this first

Free, and each takes under 5 minutes.

Let go of the walk-assist button
Turn it off and on again

In plain English

Walk assist (push mode) slowly moves the bike at up to about 6 km/h while you walk beside it. The code shows while it's on. It isn't a fault. On many displays it runs while you hold the down (-) button.

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.

1Let go of the walk-assist buttonFree Release the button you're holding (often the down (-) button). The code should go away.
2Turn it off and on againFree Switch the display off, wait 30 seconds, then switch it back on. If the code clears, note what you were doing when it appeared, in case it comes back.
3Check for a stuck buttonEasy Press each button on the handlebar pad a few times. A button stuck down by dirt or water can send commands non-stop. Clean around it and check the pad's cable and plug.

Parts you might need

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Only buy a part if the free steps didn't fix it. Always match the voltage and connector type to your bike.

Display button pad (remote)
Replaces a sticky or broken handlebar button pad. Must match your display.
Link coming soon

Still not fixed?

Pages to try next:

When it's time for a shop: if you've worked through every step and the problem is still there, take the bike to an e-bike shop. Bring your notes on when it happens, plus the code.