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Bosch error 440: Internal fault in the drive unit

Bosch BES2 (Purion, Intuvia, Kiox, Nyon)Dealer neededRide with caution

The drive unit has reported an internal error. It can be a one-off electronic glitch cleared by a restart, but a repeating 440 usually means an electronic or sensor problem inside the motor housing.

Likely causes

Momentary electronic fault cleared by a restart
Moisture inside the drive unit after pressure washing or deep water
Internal sensor or controller board failure
Overheating followed by a fault on cool-down
Loose internal connector after a hard impact

How to fix Bosch error 440

Switch off, remove the battery, wait a minute, refit and switch on
If the motor has been very wet, let the bike dry indoors for a day before testing again
Do a short test ride; note whether the code comes back under load
If it returns, a dealer must read the error memory with DiagnosticTool; do not keep riding hard on a motor that is throwing internal faults

Go to a dealer if: A dealer with DiagnosticTool is needed whenever 440 returns after a restart, to read the internal error memory and decide between repair and drive unit exchange.
Warranty: Bosch drive units, batteries and displays carry a 2-year manufacturer warranty in most markets; a genuine internal fault within that period is normally replaced free through the dealer.
Typical cost: Out of warranty, a repeating internal fault usually ends in a drive unit exchange at 500-1000 EUR/USD; independent motor repair specialists are often 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 440 myself?

You can restart and the code may clear, but you cannot reset the underlying fault. If it comes back, the drive unit needs a dealer diagnosis.

Can I keep riding with error 440?

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 440 covered by warranty?

Bosch drive units, batteries and displays carry a 2-year manufacturer warranty in most markets; a genuine internal fault within that period is normally replaced free through the dealer.

Related Bosch codes

500 · Internal fault in the drive unit 505 · Internal fault in the drive unit 511 · Internal fault in the drive unit 510 · Internal sensor error

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