Home › Bafang › Error 03

Bafang error 03: Brake signal active

Bafang UART systems (BBS01/BBS02/BBSHD, hub drives with C961/500C/850C/DP C18 UART)Fix at homeRide with caution

The controller sees a brake cut-off signal, so it refuses to give motor power. Usually the bike still rolls and the display works, but there is no assist and no throttle. On most Bafang systems this shows at power-up if a brake lever is pulled or a brake sensor is stuck.

Likely causes

A brake lever was pulled while switching the bike on
Brake sensor (magnet or hydraulic switch) stuck in the 'applied' position or misadjusted
Damaged, pinched or waterlogged brake sensor cable or connector
Wrong brake sensor type (normally-open vs normally-closed) after a replacement
Brake sensor connector plugged into the wrong port on the harness

How to fix Bafang error 03

Switch the bike off, make sure no brake lever is touched, and switch it on again
Check both brake levers return fully; adjust cable tension or the sensor magnet so it sits flush at rest
Unplug one brake sensor at a time and power on: if the error disappears, that sensor or its cable is the culprit
Inspect the cable from lever to harness for cuts, crushed sections or water in the connector; dry and re-seat
Replace the faulty brake sensor (cheap, plug-and-play) and confirm it is the correct type for your controller
If the error persists with both sensors unplugged, the controller input is faulty: shop or controller replacement

Go to a dealer if: Go to a shop if the code stays with both brake sensors disconnected, or if you cannot find the cable damage yourself.
Warranty: Bafang parts are usually sold through dealers or online resellers; warranty is typically 1-2 years via the seller, and this code alone is rarely a warranty claim.
Typical cost: A replacement Bafang brake sensor is roughly EUR/USD 10-25; a controller is EUR/USD 80-200 if the input itself is dead.

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 Bafang error 03?

Yes: switch off, release both brake levers, switch on. If it comes back, a brake sensor or its cable is sending a permanent signal.

Can I keep riding with error 03?

You can pedal without assist and ride home safely, but the motor will not help until the brake signal clears.

Is error 03 a warranty issue?

Rarely. A stuck or damaged brake sensor is a cheap wear part; only a dead controller input would be a real warranty case.

Related Bafang codes

04 · Throttle not in home position 25 · Torque sensor signal error

Not an official Bafang document. Compiled from workshop experience and public service information; details can differ per system version and bike brand.