Bosch error 820: Fault in the front wheel speed sensor cable
The ABS unit has lost the front wheel speed sensor: open circuit or short in the cable or connector. The ABS warning lamp stays on and ABS is switched off, but the brakes work as normal brakes and the motor keeps assisting.
Likely causes
- Cable chafed or cut at the fork leg
- Connector pulled loose when the wheel was removed
- Corrosion in the connector
- Cable damaged in a crash
- Sensor failed internally
How to fix Bosch error 820
- Check the sensor plug at the fork and push it home
- Follow the cable from the sensor to the ABS unit looking for cuts or pinches
- Restart and test
- If the code persists, a dealer must test the circuit and replace the sensor or cable
Warranty: The ABS module is a Bosch component with the same 2-year warranty as the rest of the system; damaged sensor cables or bent sensor brackets from crashes are not covered.
Typical cost: A sensor or cable is about 30-60 EUR/USD plus labour.
Frequently asked
Can I reset Bosch error 820 myself?
Only by fixing the connection and restarting; a broken cable has to be replaced.
Can I keep riding with error 820?
Usually, but with reduced or interrupted assistance and the risk of the system shutting down mid-ride. Ride home carefully or on muscle power alone; do not plan long rides until the cause is found.
Is error 820 covered by warranty?
The ABS module is a Bosch component with the same 2-year warranty as the rest of the system; damaged sensor cables or bent sensor brackets from crashes are not covered.
Related Bosch codes
Not an official Bosch document. Compiled from workshop experience and public service information; details can differ per system version and bike brand.