Ride1Up 700 Series/LMT'd — Error Code E21
Reviewed by certified eBike technicians · Last updated July 15, 2026
Quick Answer
E21 on Ride1Up = Speed sensor signal lost — wheel rotation not detected by controller
Severity: Check soon — speed reading lost · Limited riding OK, diagnose soon
Error E21 on your Ride1Up indicates: Speed sensor signal lost — wheel rotation not detected by controller.
Check soon — speed reading lost — Speed sensor signal lost — wheel rotation not detected by controller
Symptoms
- E21 on display; speedometer shows 0 even while riding; motor may default to reduced power mode; PAS assist levels may not respond correctly
Common Causes
- Speed sensor magnet fell off or shifted on rear wheel spoke
- Speed sensor pickup on chainstay moved out of detection range
- Sensor wire damaged from road debris or chain slap
- Magnet-to-sensor gap exceeds 10mm — signal too weak
- Speed sensor connector loose or corroded at controller
Fix Steps
Step 1: 1. Inspect the speed sensor magnet on rear wheel spokes — Ride1Up uses a standard 5mm spoke-mount magnet
Step 2: 2. If magnet is missing: replace with any compatible spoke magnet (5mm diameter) and secure with thread-lock
Step 3: 3. Check the sensor pickup on the chainstay — should be within 5-8mm of the magnet as it passes
Step 4: 4. Clean both the magnet face and sensor pickup with a dry cloth
Step 5: 5. Spin the rear wheel by hand and observe display speed reading — should show non-zero value
Step 6: 6. If still showing 0: trace the sensor wire from chainstay to controller for cuts or pinch damage
Step 7: 7. Replacement speed sensor kit: ~$10-15 online, or contact Ride1Up support for OEM part
Related Error Codes
Error E07
Controller overtemperature — internal controller temperature exceeded 80°C safety threshold
Error E10Battery communication error — BMS and controller lost communication link
Error E03Motor hall sensor fault — controller cannot read motor rotor position
Error E12Throttle signal abnormal — throttle position sensor reading outside expected range
Always disconnect the battery before inspecting wiring.