Shimano STEPS error E255: Battery reports an internal electrical fault
The battery management system has detected an electrical abnormality inside the battery pack itself, such as a cell imbalance, overcurrent, or an internal sensor reading out of range. As a safety response, motor assistance is switched off and the system will not return to normal operation while the fault is active. Walk assist is also disabled, so the bike has to be moved under human power only.
| Drive system | Shimano STEPS (E5000, E6100, E7000, E8000, EP6, EP801) |
| Severity | Dealer needed |
| Keep riding? | Do not keep riding |
| Typical cost | Expect a dealer diagnostic at 50 to 100 EUR and a replacement Shimano battery typically between 450 and 900 EUR fitted, depending on capacity and STEPS model. |
Likely causes
- Cell degradation or imbalance after heavy use, age, or deep discharge
- Moisture ingress into the battery housing, contacts, or mounting rail
- Damaged, bent, or corroded battery connector pins on the frame or pack
- Use of a non-approved or faulty charger that stressed the cells
- Internal BMS sensor or board failure inside the battery pack
How to fix Shimano STEPS error E255
- Switch the system off and remove the battery from the frame.
- Inspect the battery contacts and the frame mount for moisture, dirt, or bent pins, then clean and dry them.
- Re-seat the battery firmly and power the bike on to check whether E255 clears.
- Charge the battery fully with the original Shimano charger and retry the system.
- If the code returns, stop using the bike and contact the place of purchase or a Shimano dealer for a battery diagnostic.
- Do not open, drop, or attempt to repair the battery pack yourself; it must be handled as a dealer-level job.
Warranty: An internal battery electrical fault on a genuine Shimano pack within the two-year warranty window is normally treated as a covered component defect, while water ingress, crash damage, or use of a non-approved charger is recorded as out of warranty.
Typical cost: Expect a dealer diagnostic at 50 to 100 EUR and a replacement Shimano battery typically between 450 and 900 EUR fitted, depending on capacity and STEPS model.
Frequently asked
Can I reset shimano error E255?
A power cycle with the battery removed and re-seated sometimes clears it if the trigger was a transient contact issue, but a true internal battery fault will return. Repeated resets do not fix the underlying problem and the battery still needs checking.
Is it safe to keep riding with E255?
No. The system has cut assistance to protect the battery, and continuing to ride risks leaving you stranded or causing further damage to the pack. Stop riding and arrange a dealer inspection.
How much will the repair cost and is it under warranty?
A diagnostic runs 50 to 100 EUR and a new Shimano battery is typically 450 to 900 EUR fitted, depending on capacity. A genuine internal fault inside the two-year warranty period is usually covered, but water damage or non-approved charger use is not.
Related Shimano STEPS codes
Manuals and video
Official source: si.shimano.com
Not an official Shimano STEPS document. Compiled from workshop experience and public service information; details can differ per system version and bike brand.