Riding your Bafang-powered e-bike is an exhilarating experience—until a mysterious numbered code pops up on your display and the motor cuts out. Don’t panic. Most Bafang BBS errors can be fixed with a few simple tools and the right knowledge.
In this guide, we break down every major error code for the BBS01, BBS02, and BBSHD systems, including a deep dive into the notorious Error 30, and provide step-by-step solutions to get you back on the road.
1. The Pre-Check: First Steps for Every Error
Before diving into the codes, perform these three “Quick Fixes” which resolve 40% of all issues:
- Power Cycle: Turn the system off, wait 30 seconds, and turn it back on.
- Check the Battery: Ensure your battery is fully seated and the voltage matches your controller’s requirements.
- Inspect the 1T4 Cable: Check the main wiring harness (the big cable from the handlebars to the motor) for loose plugs or bent pins.
2. Bafang BBS Series Error Code Table
| Fault Code | Fault Cause | Troubleshooting for Hub Motor System | Troubleshooting for Mid-Drive Motor System |
|---|---|---|---|
| 05 | Throttle grip not returning to neutral position | 1. Check if the throttle grip has returned to the neutral position 2. Check if the throttle grip connector is fully inserted, and if the wiring harness is damaged (from the throttle grip outlet port to the throttle grip outlet port on the controller) 3. Faulty component troubleshooting: 1) Replace the throttle grip 2) Replace the controller | 1. Check if the throttle grip has returned to the neutral position 2. Check if the throttle grip connector is fully inserted, and if the wiring harness is damaged (from the throttle grip outlet port to the throttle grip outlet port on the controller) 3. Faulty component troubleshooting: 1) Replace the throttle grip 2) Replace the controller |
| 07 | Battery overvoltage protection | 1. Check if the rated voltage of the battery matches the rated voltage of the controller 2. Faulty component troubleshooting: 1) Replace the battery 2) Replace the controller | 1. Check if the rated voltage of the battery matches the rated voltage of the drive unit 2. Faulty component troubleshooting: 1) Replace the battery 2) Replace the drive unit |
| 08 | Motor hall sensor abnormality (only for motors with temperature sensors) | 1. Check if the motor connector is fully inserted, and if the wiring harness is damaged (from the motor outlet port to the motor outlet port on the controller) 2. Faulty component troubleshooting: 1) Replace the motor 2) Replace the controller | Replace the drive unit |
| 09 | Motor phase wire abnormality | 1. Check if the motor connector is fully inserted, and if the wiring harness is damaged (from the motor outlet port to the motor outlet port on the controller) 2. Faulty component troubleshooting: 1) Replace the motor 2) Replace the controller | Replace the drive unit |
| 10 | Motor overheat protection (only for motors with temperature sensors) | 1. If riding for a long time, stop the vehicle to let the motor cool down 2. If not riding or riding for a short time, faulty component troubleshooting: 1) Replace the motor 2) Replace the controller | 1. If riding for a long time, stop the vehicle to let the drive unit cool down 2. If not riding or riding for a short time, replace the drive unit |
| 11 | Motor temperature sensor abnormality (only for motors with temperature sensors) | 1. Check if the motor connector is fully inserted, and if the wiring harness is damaged (from the motor outlet port to the motor outlet port on the controller) 2. Faulty component troubleshooting: 1) Replace the motor 2) Replace the controller | Replace the drive unit |
| 12 | Current sensor abnormality | Replace the controller | Replace the drive unit |
| 14 | Controller overheat protection | 1. If riding for a long time, stop the vehicle to let the controller cool down 2. If not riding or riding for a short time, replace the controller | 1. If riding for a long time, stop the vehicle to let the drive unit cool down 2. If not riding or riding for a short time, replace the drive unit |
| 15 | Controller temperature sensor abnormality | Replace the controller | Replace the drive unit |
| 21 | Speed sensor abnormality | 1. Check if the motor connector is fully inserted, and if the wiring harness is damaged (from the motor outlet port to the motor outlet port on the controller) 2. Faulty component troubleshooting: 1) Replace the motor 2) Replace the controller | 1. Check if the magnet steel has fallen off, or if the induction distance between the magnet steel and the speed sensor is within the normal range 2. Check if the speed sensor connector is fully inserted, and if the wiring harness is damaged (from the speed sensor outlet port to the speed sensor outlet port on the drive unit) 3. Faulty component troubleshooting: 1) Replace the speed sensor 2) Replace the drive unit |
| 26 | Bottom bracket assist torque sensor abnormality (only for systems with assist torque sensors) | 1. Check if the bottom bracket assist sensor connector is fully inserted, and if the wiring harness is damaged (from the bottom bracket assist sensor outlet port to the bottom bracket assist sensor outlet port on the controller) 2. Faulty component troubleshooting: 1) Replace the bottom bracket assist sensor 2) Replace the controller | Replace the drive unit |
| 30 | Communication abnormality | 1. Check if the display connector is fully inserted, and if the wiring harness is damaged (from the display outlet port to the display outlet port on the controller) 2. Faulty component troubleshooting: 1) If the display auto powers off 20 seconds after error code 30 is reported, replace the controller 2) If the display does not auto power off 20 seconds after error code 30 is reported, replace the display 3) If a BESST tool is available, connect the BESST between the display and the controller, read the information of the display and controller, and replace the component whose information cannot be read | 1. Check if the display connector is fully inserted, and if the wiring harness is damaged (from the display outlet port to the display outlet port on the drive unit) 2. Faulty component troubleshooting: 1) If the display auto powers off 20 seconds after error code 30 is reported, replace the drive unit 2) If the display does not auto power off 20 seconds after error code 30 is reported, replace the display 3) If a BESST tool is available, connect the BESST between the display and the drive unit, read the information of the display and drive unit, and replace the component whose information cannot be read |
| 36 | ON/OFF button detection circuit abnormality (only for systems using Bafang CAN communication protocol) | 1. Holding down the ON/OFF button continuously during startup will trigger this warning, and the warning will disappear after releasing the button 2. Faulty component troubleshooting: 1) Replace the display 2) Replace the controller | 1. Holding down the ON/OFF button continuously during startup will trigger this warning, and the warning will disappear after releasing the button 2. Faulty component troubleshooting: 1) Replace the display 2) Replace the drive unit |
| 37 | Watchdog abnormality | Replace the controller | Replace the drive unit |
| 42 | Battery total discharge voltage too low (only for batteries with intelligent communication and using Bafang communication protocol) | 1. Plug in the charger to charge, and check if the fault is resolved 2. Replace the battery | 1. Plug in the charger to charge, and check if the fault is resolved 2. Replace the battery |
| 49 | Single battery cell discharge voltage too low (only for batteries with intelligent communication and using Bafang communication protocol) | 1. Plug in the charger to charge, and check if the fault is resolved 2. Replace the battery | 1. Plug in the charger to charge, and check if the fault is resolved 2. Replace the battery |
| 4C | Voltage difference between individual battery cells (only for batteries with intelligent communication and using Bafang communication protocol) | Replace the battery | Replace the battery |
3. Deep Dive: Cracking the “Error 30” Mystery
Error 30 is the most complex code because it isn’t a single part failure—it’s a communication breakdown. To fix it, you must understand the “language” your motor speaks.
Physical vs. Protocol Failure
Most Error 30 issues stem from one of two areas:
A. The Physical Link
The BBS system uses a 5-pin green connector for the display. If water enters this connector or a pin is slightly bent, the signal is lost.
- The Fix: Unplug the display, clean the pins with electrical contact cleaner, and ensure the arrows on the connectors align perfectly when re-inserting.
B. Protocol Mismatch: UART vs. CAN Bus
This is a common “hidden” issue. Bafang uses two distinct communication protocols that are not compatible:
- UART (Universal Asynchronous Receiver-Transmitter): Used in almost all classic BBS01/02 and BBSHD kits. Uses a 5-pin round connector.
- CAN Bus (Controller Area Network): Found in newer Bafang M-series and a few recent BBS batches. These often have a different internal wiring logic despite having similar-looking plugs.
- The Trap: If you buy a UART display (like a standard 500C or 850C) and plug it into a CAN Bus controller, you will get an instant Error 30. The hardware is fine, but the “languages” don’t match.
Expert Troubleshooting Tip
If you are getting Error 30, try the “Bypass Test”: Disconnect your brake sensors and throttle, leaving only the display and motor connected. If the error disappears, one of your peripherals was shorting the communication line.
4. How to Prevent Future Failures
- Waterproofing: While Bafang kits are IP65 rated, we recommend using heat-shrink tubing or dielectric grease on the 1T4 connectors if you ride in heavy rain.
- Chainline Maintenance: Ensure your chain is properly aligned. High stress on the motor due to a poor chainline can lead to Error 10 (overheating).
- Firmware Safety: Avoid “over-clocking” your controller settings beyond factory limits, as this often leads to Error 08 or 09.
5. Need Parts or Technical Support?
Still seeing a code on your screen? We are here to help.
- Looking for Replacement Parts? We stock genuine Bafang Throttles, Controllers, and Displays for all BBS models.
- B2B & Wholesale: Are you a repair shop owner? We provide bulk pricing and technical documentation for Bafang systems.
- Free Compatibility Check: Not sure if your motor is UART or CAN Bus? Send us a photo of your motor serial number via WhatsApp, and our engineers will identify the correct parts for you.