91 | Controller - Controller FET circuit error

Written by Alex Kovell

Last published at: September 9th, 2025

Description

The system has detected a fault in the controller's FET detection circuit.The drive component in the controller may be open-circuited or malfunctioning.

⚠️Triggers of Error Code

The following are possible causes of error code 91:

  • Controller is malfunctioning

1 E-bike remains stationary

Before proceeding with the e-bike inspection, ensure the bike is stationary, and do not sit on the bike, pedal, or apply any force to the pedals.
Long press the power button to turn off the e-bike.

 
 

2 Replace the Controller

Replace the [Controller] with a new spare, then reboot the e-bike to check if the error code still exists. If this doesn't fix the issue, proceed to the next step.

 
 

3 Reach out to the Service Team if you need additional support!

Contact Customer Care or the Hyena Service Center for further technical assistance.

 
 

 


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