Error 21: Speed Sensor Troubleshooting Guide

What is Error 21?

Error 21 indicates a speed sensor malfunction on your e-bike. This error typically occurs when the bike's control system cannot properly communicate with the speed sensor, which monitors wheel rotation and provides critical data for motor operation.

Safety Requirements

IMPORTANT: Before performing any troubleshooting steps, you must:

1. Power the bike completely OFF
2. Remove both batteries from the bike

Warning: Failure to properly power down the bike and remove batteries before working on electrical components may cause damage that is not covered under warranty.

Basic Troubleshooting Steps

Step 1: Motor Cable Reconnection

The most common solution for Error 21 is to reset the motor cable connection:

1. Ensure the bike is powered OFF and batteries are removed
2. Locate the motor cable connection (usually near the rear wheel/motor area)
3. Carefully disconnect the motor cable by gently pulling apart the connector
4. Inspect the connector pins for any dirt, corrosion, or damage
5. Reconnect the motor cable ensuring it is:
   • Fully seated in the connector
   • Pushed together completely
   • Secure and tight
6. Reinstall the batteries
7. Power on the bike and check if Error 21 has cleared

Step 2: Cable Inspection

If reconnecting the motor cable doesn't resolve the issue, perform a thorough cable inspection:

1. Follow all safety requirements (bike OFF, batteries removed)
2. Visually inspect the motor cablealong its entire length for:
   • Cuts or nicks in the cable jacket
   • Pinched or crushed areas
   • Signs of wear where the cable rubs against the frame
   • Loose or damaged connectors
3. Check cable routingto ensure it's not:
   • Pinched by frame components
   • Rubbing against moving parts
   • Stretched or under tension during steering
4. Examine the speed sensor(if accessible) for:
   • Physical damage
   • Proper mounting position
   • Debris blocking the sensor

When to Contact Support

Contact technical support if:

• Error 21 persists after cable reconnection
• You discover visible cable damage during inspection
• You're uncomfortable performing these troubleshooting steps
• The error returns frequently after clearing

Important Warranty Information

Please Note: Damage caused by working on electrical components without properly powering down the bike and removing batteries is not covered under warranty. Always follow proper safety procedures before performing any maintenance or troubleshooting.

Prevention Tips

To avoid future speed sensor errors:

• Regular maintenance: Inspect cables monthly for signs of wear
• Proper storage: Avoid storing the bike in areas where cables might be pinched or damaged
• Careful handling: Be mindful of cable routing when transporting or servicing the bike
• Professional service: Have your bike inspected by a qualified technician annually

Still experiencing issues? Contact our technical support team at [email protected] with your bike's serial number and a description of the troubleshooting steps you've already performed.