Bafang error 27: Controller over current
Bafang CAN systems (M400/M500/M600/M620, DP C18 CAN, 850C/860C CAN)Dealer neededDo not keep riding
The controller measured a current above its hard limit and shut down to protect itself. Riders usually see it under hard acceleration or on a stalled motor. A single event can be a glitch; repeated 27 means a motor or controller problem.
Likely causes
- Motor phase short or partially burnt winding
- Motor stalled against a load (wheel blocked, chain jammed on a mid-drive)
- Failing MOSFET in the controller
- Water in the motor connector causing a phase-to-phase leak
- Current limit raised beyond the controller rating
How to fix Bafang error 27
- Power cycle once and test gently at low assist
- Check the wheel and drivetrain spin freely; clear any jam
- Inspect the motor connector for water or burnt pins
- Reset any raised current limits to stock
- Have the motor phases and controller tested; replace the faulty part
Go to a dealer if: Go to a shop after the second occurrence; over-current faults escalate into destroyed controllers.
Warranty: If the bike or kit is under warranty (usually 1-2 years via the seller), contact them before opening anything, as opened motors and controllers can void the claim.
Typical cost: Controller EUR/USD 100-300; motor EUR/USD 250-600 on M-series units.
Warranty: If the bike or kit is under warranty (usually 1-2 years via the seller), contact them before opening anything, as opened motors and controllers can void the claim.
Typical cost: Controller EUR/USD 100-300; motor EUR/USD 250-600 on M-series units.
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 error 27?
Power cycle clears a one-off. If it repeats, stop riding.
Can I keep riding?
No, not with a repeating 27. Pedal home.
Warranty?
Yes if the setup is stock; raised current limits void it.
Related Bafang codes
Not an official Bafang document. Compiled from workshop experience and public service information; details can differ per system version and bike brand.