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Bosch error 423: Battery connection problem

Bosch BES2 (Purion, Intuvia, Kiox, Nyon)Fix at homeRide with caution

The system loses contact with the battery or cannot read its data. The bike may cut out, refuse to start, or show the battery gauge dropping to zero. Very often this is a contact issue rather than a dead battery.

Likely causes

Battery not pushed fully home or not locked in its mount
Dirty, oxidised or wet contacts on the battery or the frame-side connector
Damaged cable between the battery mount and the drive unit
Battery mount loose on the frame so the contacts move while riding
Battery management system (BMS) has switched the battery off after a fault

How to fix Bosch error 423

Switch off, remove the battery and check the contacts on the battery and in the mount
Clean the contacts with a dry cloth or a pencil eraser; a little contact spray is fine, no grease
Refit the battery firmly until the lock clicks; try wiggling it, it should not move
Charge the battery on the charger for a while and check the charger LED behaves normally
Switch on and test; if it happens on bumps, check whether the mount bolts are loose
If a clean, locked battery still throws the code, a dealer needs to test the battery and mount cable

Go to a dealer if: A dealer is needed when the contacts are clean and the battery is locked but the error persists, or when the mount cable is damaged and needs replacing.
Warranty: Dirty contacts, damaged cables and water ingress are treated as wear or user damage and are rarely covered; a genuine component fault within the 2-year warranty normally is.
Typical cost: Usually free if it is contacts or seating; a replacement mount or cable is about 30-80 EUR/USD plus labour, a battery 500-900 EUR/USD.

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 423 myself?

Yes, in most cases. Clean the contacts, seat and lock the battery properly and restart. There is no menu reset; the code disappears when the connection is stable.

Can I keep riding with error 423?

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 423 covered by warranty?

Dirty contacts, damaged cables and water ingress are treated as wear or user damage and are rarely covered; a genuine component fault within the 2-year warranty normally is.

Related Bosch codes

530 · Battery error 422 · Drive unit connection problem 606 · External battery error

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