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Troubleshooting

Bafang mid drive and hub motor troubleshooting and error codes

Safe checks for e-bikes and conversion kits with Bafang mid drives or hub motors, including BBS kits: what the display codes mean as Bafang states them, connector and speed sensor checks, and when a shop is needed.

Last edited Nov 8, 2026 by Pedalwise team Edit History Add a subpage

The Pedalwise team started this page from official manuals, support pages and repair videos. Fixed this yourself, or spotted something wrong? Help improve it.

Battery and electrical safety. Lithium-ion batteries can catch fire if they're damaged or charged wrong. Never open a battery pack, and stop using any battery that's swollen, hot, wet or smells burnt. Every edit to this page is checked by a second person before it goes live.

Bafang makes mid drive motors, hub motors, displays and batteries used by many bike brands, and its BBS series is a common choice for conversion kits. This page covers safe checks a rider can do, Bafang's own error code list and what to leave to a shop. For the bigger picture see our systems overview.

Before you start

  • Identify your motor and display. Bafang motor model names start with letters such as MM, RM or FM, and display names start with DP. The label is on the part. Manuals for many models are on Bafang's user manual page and dealer manual page. Kit sellers often supply their own manual too.
  • Know your display type. Bafang groups its displays as TFT LCD, matrix LCD or segment LED (Bafang displays). Names ending in .CAN use the CAN bus. The DP C11.CAN manual, for example, plugs into an EB-Bus connector.
  • Keep the QR code label on the display cable. Bafang says it is needed for future software updates.
  • Switch off and remove the battery before touching any connector.

Common problems and what to check

Display won't turn on

  • Charge the battery and check it is fully seated.
  • On the DP C11, press and hold the power button for more than 2 seconds. Your display's manual gives its own steps.
  • Check the display connector is pushed fully home. Bafang's DP C11 manual says to keep both halves in line and press firmly.
  • Bafang's next step for a dead display (common fault CF02) is swapping in a known good display, which is shop work (CF02 sheet).
  • See e-bike won't turn on and display blank or flickering.

Error 30, or the system keeps dropping out

  • Bafang's first check for 30 is every connector on the control harness. Look for loose plugs, corrosion, bent or broken pins, dirt, damaged insulation or a cracked shell (error 30 sheet).
  • With the battery out, unplug, inspect and firmly reconnect each one. If you find damage, stop there and take it to a shop.
  • Next steps use Bafang's BESST diagnostic tool, then new parts. That is dealer work.

Error 21 or no speed reading

  • Restart the system first.
  • Check the spoke magnet lines up with the speed sensor. Bafang's error 21 sheet gives the gap as 10 to 20 mm (error 21 sheet). Your kit's manual may differ.
  • Inspect the sensor cable and plug for damage.
  • More steps: no pedal assist and motor cuts out.

Throttle problems

  • 04 means the throttle is not returning to its rest position. Bafang's sheet says to check it for sticking and replace it if it sticks (error 04 sheet). Do not ride with a throttle that sticks. See throttle not working.

Motor stops when braking, or will not stop

  • Brake levers with cut-off sensors stop the motor on purpose. If the cut-off fails (CF04), Bafang's steps are to replace the e-brake sensor, then the controller (CF04 sheet). Have a shop do this.

Never unplug or bypass brake cut-off sensors. If the motor keeps driving when you stop pedaling or brake, switch off, remove the battery and do not ride until a shop has checked it. See e-bike brakes.

Overheating, noise and short range

  • 10 and 14 point to an overheated motor or controller. Stop and let it cool.
  • Bafang lists bearing wear, gear wear, water getting into the housing and frame resonance as causes of motor noise (Bafang FAQ). These need a shop. See e-bike noises.
  • For short range (CF08), see battery drains fast.

Error codes

On displays like the DP C11, an error shows as a two digit number and the Information menu keeps the last ten, where 00 means none. Codes and fixes can differ by display and model. These are from Bafang's FAQ, which links a solution sheet for each.

  • 04: throttle not back in position
  • 07: overvoltage protection
  • 08: hall sensor error
  • 09: motor phase winding fault
  • 10: motor over temperature
  • 11: motor temperature sensor fault
  • 12: motor overcurrent
  • 14: controller over temperature
  • 21: speed sensor fault
  • 25: torque signal fault
  • 27: controller overcurrent
  • 30: communication failed
  • 33: brake detection circuit fault
  • 41 and 42: battery total voltage too high or low
  • 45 and 46: battery temperature too high or too low
  • 48: battery state of charge too low

The DP C11 manual says to restart the system first, then contact your dealer if the code stays. See also our error codes page.

Official help

Videos

How-To: Fix Error Code 21 on Bafang's ULTRA Mid-Drive Motor from BAKCOU: Works through the Bafang error 21 speed sensor fault on an Ultra mid drive by checking the sensor, magnet and plug.

When to get a pro

  • Any code that returns after a restart, and any code in the 40s, which relate to the battery.
  • Hall sensor, phase winding, overcurrent or temperature sensor codes. These point inside the motor or controller.
  • Damaged connectors, pins or cables.
  • Controller updates. Pedalwise does not cover reprogramming to change power or speed settings.

Battery, controller and wiring faults need a pro. Never open a battery pack or try to reset it. See battery won't charge, e-bike battery care and when to call a pro.

Sources

Stuck after these checks? Find a shop near you.

In this section

Need a pro?

If these steps didn't fix it, find a shop near you in our partner network. For battery or wiring trouble, look for shops marked Battery and electrical.

Talk

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