Shimano STEPS error E259: Electrical fault detected in the battery

Shimano STEPS (E5000, E6100, E7000, E8000, EP6, EP801)Dealer neededDo not keep riding

The battery management system has flagged an internal electrical abnormality, typically a cell voltage out of range or a BMS self-check failure. As a result, the drive unit cuts motor assistance immediately and the bike will not deliver power until the fault clears. Walk assist, lights powered from the battery, and the cycle computer remain off or behave erratically while the code is active.

Drive system	Shimano STEPS (E5000, E6100, E7000, E8000, EP6, EP801)
Severity	Dealer needed
Keep riding?	Do not keep riding
Typical cost	Diagnostic fees run €40–€90 and a replacement Shimano STEPS battery typically costs €450–€900 depending on capacity and model.

Likely causes

Degraded or imbalanced cell group inside the battery pack
Loose or corroded communication connector between battery and drive unit
Water or moisture ingress into the battery housing or contacts
Faulty BMS firmware or failed internal sensor on the battery PCB
Old age battery with capacity below usable threshold triggering protection logic

How to fix Shimano STEPS error E259

Switch the system off and remove the battery from the frame.
Inspect the battery mounting rail, terminals and the drive unit socket for dirt, moisture or bent pins; clean and dry if needed.
Reseat the battery firmly and power the bike on without pedalling to see if the code clears.
If the code returns, leave the battery off for 10 minutes, then try a full charge cycle on a known-good Shimano charger.
Check the charger's LED behaviour; a battery that refuses to charge or shuts off early confirms the pack, not the bike.
Contact the place of purchase or an authorised Shimano dealer for a diagnostic and possible battery replacement.

Go to a dealer if: A dealer is required as soon as the code reappears after a clean reseat and charge cycle, because internal battery electrical faults cannot be repaired at home.
Warranty: A genuine BMS or cell failure inside the first two years is normally treated as a Shimano warranty case, while water ingress, crash damage and batteries left stored flat are routinely excluded.
Typical cost: Diagnostic fees run €40–€90 and a replacement Shimano STEPS battery typically costs €450–€900 depending on capacity and model.

Still stuck? Take a photo of the display and show it to a local e-bike workshop. Bring the bike's system name (e.g. Bosch Performance Line CX) and the exact code; that saves diagnostic time and money.

Frequently asked

Can I reset Shimano error E259?

A power cycle sometimes clears a transient BMS flag, but E259 indicates an internal battery electrical fault that will return if the underlying problem is real. If the code reappears after a reseat and charge, the battery needs dealer-level diagnostics.

Is it safe to keep riding with E259?

No. Motor assist is already disabled and the battery is reporting a protective fault, which means voltage or current behaviour outside design limits. Continuing to cycle without assist and ignoring the warning risks further battery damage.

Will Shimano replace the battery under warranty?

If the battery is within the two-year component warranty and shows no signs of water ingress, impact or neglect, Shimano typically covers a replacement pack. Out of warranty, owners pay the full €450–€900 cost for a new unit.

Related Shimano STEPS codes

E023 · Battery electrical abnormality detected E024 · Battery overcurrent protection triggered E025 · Drive unit not recognised by battery E020 · Communication fault between battery and drive unit

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.