How to troubleshoot brake sensor errors – Biktrix

Follow this guide for how to resolve your brake sensor errors.

To perform this fix you will need a 2mm Allen Key and a 7mm Wrench.

Symptoms

Both Throttle and PAS do not work
Error 37 on Stunner LT
Error 03 Bafang motors, Stunner, Stunner X, Juggernaut Classic, Juggernaut Classic HD, Juggernaut Ultra, Juggernaut Ultra FS
This symbol is staying on screen after brakes are released

Trace the wires coming from brake sensor
Disconnect both (Left/Right yellow connectors) brake cut-off switches, ride the bike for a couple minutes and see if the issue reoccurs. If the motor stops cutting out, then there might be an issue with either one of the switches (L or R).
Connect the right brake cut-off switch. Leave the left brake cut-off switch disconnected, ride the bike for a couple minutes, see if the problem reoccurs. If the issue reoccurs then there is a problem with the Right switch.
Connect the left brake cut-off switch. Disconnect the right brake cut-off switch, ride the bike for a couple minutes, see if the problem reoccurs. If the issue reoccurs then there is a problem with the left switch.

Make sure levers are returning to original position freely
- If Bad
  - A brake adjustment is a necessary DIY found here

Tektro
- Adjust Brake sensor alignment screw
- - Loosen the set screw by a few threads with the 2mm Allen Key
  - Loosen adjustment screw 1/2 turn with 7mm Wrench
  - Check if the motor cuts off while squeezing the brake
    - If the motor still cuts off with brake released loosen the adjustment screw by 1/4 turn and try again
    - If the motor does not cut off at all with the brake pressed tighten the adjustment screw 1/4 turn and try again
    - Repeat the process until the symbol no longer stays on the display with the brakes fully released and the symbol no longer shows up when riding without the brakes activated.
    - If needed try smaller adjustments to find the "sweet spot"
  - The adjustment screw changes sensitivity of the brake cutoff switch
    - Having this screw looser will trip the cutoff with more brake pressure
    - Having this screw tighter will trip the cutoff with less brake pressure
  - Once adjustment is complete tighten the Set Screw back to it's original position.
Other
- Remove lower cover
- Check for physical blockage and smooth movement of switch
- If neither fixes contact support for replacement

Tektro
- Adjust Brake sensor alignment screw
- - Loosen set screw
  - Loosen adjustment screw 1/2 turn
  - Check if the motor cuts off while squeezing the brake
    - If the motor still cuts off with brake released loosen the adjustment screw by 1/4 turn and try again
    - If the motor does not cut off at all with the brake pressed tighten the adjustment screw 1/4 turn and try again
    - Repeat the process until the symbol no longer stays on the display with the brakes fully released and the symbol no longer shows up when riding without the brakes activated.
    - If needed try smaller adjustments to find the "sweet spot"
  - The adjustment screw changes sensitivity of the brake cutoff switch
    - Having this screw looser will trip the cutoff with more brake pressure
    - Having this screw tighter will trip the cutoff with less brake pressure
  - Once adjustment is complete tighten the Set Screw back to it's original position.

Biktrix
- First, adjust the reach screw clockwise/tighten with a 2mm Allen Key
- - Plug the brake sensor connector back into the umbilical. Check if the brake sensor error is still occurring.
  - If the brake sensor error is still occurring simply keep on tightening the screw a little bit at a time until it reaches a point where the motor no longer cuts out with the brakes disengaged.
- If adjusting the reach screw does not solve the problem you will need to adjust the brake sensor itself. Loosen the brake sensor adjustment bolt by a quarter turn.
- Plug the brake sensor connector back into the umbilical. Check if the brake sensor error is still occurring.
- If the brake sensor error is still occurring unplug the brake sensor connector and loosen the brake sensor adjustment bolt by another quarter turn. Then plug it back in and check if the error is still occurring. Repeat until error is resolved.
- When error is fully resolved plug the brake sensor in. Then zip tie the brake sensor connector wire to the brake cables at two or three points to keep it stable and adjusted.