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Shimano STEPS error E021: Battery not compatible with the system
Shimano STEPS (all drive units, shown on SC-E5000/E6100/E7000/E8000 displays and via EW-EN100 LED)Dealer neededRide with caution
E021 appears when the connected battery does not match what the drive unit expects. Typical after swapping in a second-hand or third-party battery, or after a firmware update that changed compatibility. The motor refuses to assist.
Likely causes
- Battery from a different STEPS generation or a non-Shimano battery
- Battery or drive unit firmware not updated to a matching version
- Battery has been replaced but not registered/paired via E-TUBE
- Very rarely, a battery BMS reporting a wrong ID
How to fix Shimano STEPS error E021
- Confirm the battery model matches what your bike shipped with (e.g. BT-E8010/E8020/E8035/E8036 for E8000/EP8 systems)
- If you recently updated firmware, update all components including the battery
- Try the original battery if you still have it
- Take the bike and battery to a dealer for a compatibility check and firmware update in E-TUBE
Go to a dealer if: A dealer is required: E-TUBE PROJECT checks firmware compatibility and updates the battery firmware, which is not possible in the consumer app.
Warranty: Warranty does not cover incompatible third-party batteries; a genuine battery that stopped being recognised after an update is a warranty/firmware matter.
Typical cost: A firmware update is a small labour charge; if a wrong battery was bought, the cost is a correct battery.
Warranty: Warranty does not cover incompatible third-party batteries; a genuine battery that stopped being recognised after an update is a warranty/firmware matter.
Typical cost: A firmware update is a small labour charge; if a wrong battery was bought, the cost is a correct battery.
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 E021 myself?
No, there is nothing to reset; the system needs a compatible battery or a firmware update.
Can I keep riding with E021?
You can ride without assist; the bike is otherwise safe.
Is E021 covered by warranty?
Only when a genuine, correctly matched battery is involved.
Related Shimano STEPS codes
E020 · Battery to drive unit communication errorE022 · Battery communication faultE030 · System configuration error
Not an official Shimano STEPS document. Compiled from workshop experience and public service information; details can differ per system version and bike brand.