What Shimano says
Communication error between the battery and the drive unit. Assist isn't available.
Shimano's recommended steps
- Check the cable between the battery and the drive unit is connected properly.
- Contact the shop where you bought the bike, or a Shimano dealer.
Summarized from Shimano STEPS E8080 user manual (Japanese, translated) (error E020), checked October 23, 2026. Follow the link for Shimano's exact wording.
If it keeps coming back
If the code comes back after a restart, have it 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.
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.