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Bosch error 800: Internal ABS fault

Bosch BES2 & BES3Dealer neededRide with caution

The Bosch eBike ABS control unit has detected an internal error. The ABS warning lamp stays on and ABS is switched off, but the brakes work as normal brakes and the motor keeps assisting. A restart may clear a one-off; a repeating 800 needs a dealer.

Likely causes

Internal electronics fault in the ABS unit
Water ingress into the ABS unit or its connectors
Loose plug at the ABS unit
Damage after a crash
Firmware fault

How to fix Bosch error 800

Switch the system off and on again
Check the ABS unit plugs and cables for damage or moisture (usually behind the head tube or under the down tube)
Test ride gently; the ABS lamp should go out after the first few metres if ABS is healthy
If the lamp stays on or the code returns, a dealer must read the ABS unit with DiagnosticTool

Go to a dealer if: A dealer with DiagnosticTool is needed whenever 800 persists, to read the ABS error memory and test or replace the unit.
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: An ABS control unit is expensive, typically 400-700 EUR/USD plus fitting; a cable or connector repair is far cheaper.

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 Bosch error 800 myself?

Only by restarting. The ABS fault memory is cleared by the dealer.

Can I keep riding with error 800?

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 800 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

810 · Implausible signals from the wheel speed sensor 860 · ABS power supply fault 870 · ABS communication error

Not an official Bosch document. Compiled from workshop experience and public service information; details can differ per system version and bike brand.