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Shimano STEPS error codes

Shimano error E021
Battery not supported by this system

The battery fitted isn't one this motor supports. Use the battery made for your system.

Checked against Shimano's own manual: October 23, 2026.

A short list, on purpose. These are the Shimano codes we could confirm in Shimano's own manuals. Most come from Shimano's Japanese manual for the E8080 system and are translated, so follow each source link for Shimano's exact wording. For any code not listed, use Shimano's official lookup at si.shimano.com/error.
Battery hot, swollen, leaking or smells strange? Stop and read battery safety first. If there's smoke, get away and call 911.

What Shimano says

The battery meets the system's standards but isn't supported by this drive unit. Assist isn't available.

Shimano's recommended steps

  1. Press the battery's power button to restart it.
  2. Contact the shop where you bought the bike, or a Shimano dealer.

Summarized from Shimano STEPS E8080 user manual (Japanese, translated) (error E021), checked October 23, 2026. Follow the link for Shimano's exact wording.

If it keeps coming back

If the code comes back after one restart, stop using the assist and have the bike checked by a mechanic who works on Shimano systems. Bikes Plus has diagnostic tools for Shimano and most other major motor systems.

Write down the code and what you were doing when it appeared. That saves time at the shop.

Call Bikes Plus Email a photo

Make sure it's a Shimano code

Error numbers mean different things on different systems. This page covers Shimano STEPS and EP e-bike systems. Codes starting with W are warnings, which clear when conditions improve; codes starting with E are errors, which point to a possible fault. Shimano's E-TUBE PROJECT Cyclist app can read the code from the bike.

All Shimano codes Step-by-step checks