Yamaha PW error E21: Crank / cadence sensor error
Yamaha PW series (PW-X3, PW-X2, PW-X, PW-ST, PW-TE, PW-SE, PW-CE) and Giant/Liv SyncDriveFix at homeRide with caution
E21 means the drive unit cannot detect crank rotation properly. Assist starts late, drops out while pedalling or does not come on. It is usually mechanical at the crank rather than electronic. Also shown on Giant/Liv (SyncDrive) bikes, sometimes with a leading zero (E01) or as 'Er' followed by the number on older Yamaha displays.
Likely causes
- Crank arm loose
- Chainring bolts loose or chainring bent
- Debris or a bent chainguard interfering
- Cadence sensor failure inside the drive unit
How to fix Yamaha PW error E21
- Check and tighten both crank arms and the chainring bolts
- Spin the cranks backwards and check nothing rubs
- Power-cycle
- If the cranks are tight and E21 remains, dealer diagnostic
Go to a dealer if: Dealer with the Yamaha/Giant diagnostic tool (Yamaha PW diagnostic or Giant's RideControl/e-bike diagnostic software) is needed to read the fault log and test the component when the home checks do not clear the code.
Warranty: Component faults inside the drive unit, battery or display are covered by the bike brand's warranty via the dealer; damage from crashes, water ingress or tuning devices is not.
Typical cost: Usually free / DIY; an internal sensor fault means a drive unit repair.
Warranty: Component faults inside the drive unit, battery or display are covered by the bike brand's warranty via the dealer; damage from crashes, water ingress or tuning devices is not.
Typical cost: Usually free / DIY; an internal sensor fault means a drive unit repair.
Still stuck? Take a photo of the display and show it to a local e-bike workshop. Bring the bike's system name (e.g. Bosch Performance Line CX) and the exact code; that saves diagnostic time and money.
Frequently asked
Can I reset E21 myself?
Yes, after fixing anything loose at the crank and power-cycling.
Can I keep riding with E21?
Yes, with unreliable assist until fixed.
Is E21 covered by warranty?
Yes for an internal sensor within the warranty period.
Related Yamaha PW codes
Not an official Yamaha PW document. Compiled from workshop experience and public service information; details can differ per system version and bike brand.