Error 21 indicates there is an issue with the amount of voltage or current being supplied to the internal controller and motor.

This can often be resolved by resetting the display. Carefully removing the battery, inspecting the terminals and re-installing the battery gently.

However, if the issue persists, typically the issue is: 

  • 50% Internal controller
  • 30% Motor
  • 10% Battery
  • 10% Wire from motor to controller (if it shows signs of damage at connections)

First, try resetting your display to default. This is done from the main screen by holding the middle (Power) and top (+) button on your display at the same time. Select reset to default 'yes' and hold the middle button to enter that setting. These steps can be reviewed in our display tutorials:

If you have access to another bike (with matching specs or components), you can potentially test the motor easily or swap the internal controller, which could expedite the resolution. Advanced troubleshooting steps:


Next, follow this guide on checking wires and connections. Please take pictures where requested to share with our support team if necessary. This will likely resolve this issue faster. 

500 Series Motor Not Working

700 Series Motor Not Working

LMT'D Motor Not Working

Core-5 Motor Not Working

After you have checked your connections and reset your display. It is an appropriate time to contact our support team and share clear pictures.