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Bosch error 504: Speed signal manipulation detected

Bosch BES2 & BES3WarningDo not keep riding

The drive unit has detected an implausible speed signal and assumes tuning. Assistance is switched off or reduced to a walk-assist level for the rest of the ride, and the event is written to the drive unit's memory. It also appears without any tuning when the spoke magnet or speed sensor is out of position.

Likely causes

A tuning dongle or chip is fitted, or was fitted and removed without a dealer reset
Spoke magnet moved, loose or turned so it no longer passes the sensor at the correct distance
Speed sensor cable damaged or the sensor plug loose
Wrong wheel circumference written in the system, or a different wheel size fitted
Speed sensor dirty, bent or fouled by mud so it misses pulses

How to fix Bosch error 504

Switch the system off
Check the spoke magnet: it must sit opposite the mark on the sensor, a few millimetres away, and be tightly fixed on the spoke
On rim-magnet systems (BES3, rear-wheel disc sensor), check the sensor bolts and that the magnet ring is clean
Inspect the sensor cable along the chainstay for cuts or a loose plug
Remove any tuning device completely
Restart the system and ride a few hundred metres; if the code returns, a dealer must reset the drive unit with DiagnosticTool and check the wheel circumference setting

Go to a dealer if: A dealer with DiagnosticTool is needed when the code stays after correcting the magnet and sensor, because the error has to be cleared in the drive unit and the wheel size verified.
Warranty: Bosch logs tuning and speed-signal manipulation in the drive unit; if the dealer's DiagnosticTool shows a manipulation history, Bosch will usually refuse a warranty claim on the drive unit.
Typical cost: Free if it is magnet alignment; a new speed sensor is about 20-40 EUR/USD, a dealer reset 30-60 EUR/USD; a tuning-related motor failure is on you.

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 504 myself?

Often yes: fix the magnet or sensor position and restart. On some systems the block persists for the ride and clears on the next start; if it does not, the dealer must clear it in the drive unit.

Can I keep riding with error 504?

No, not with assistance. The system switches the motor off for this code. The bike still works as a normal pedal bike, so you can ride home on muscle power, but the fault has to be cleared before assistance comes back.

Is error 504 covered by warranty?

Bosch logs tuning and speed-signal manipulation in the drive unit; if the dealer's DiagnosticTool shows a manipulation history, Bosch will usually refuse a warranty claim on the drive unit.

Related Bosch codes

510 · Internal sensor error 500 · Internal fault in the drive unit 550 · Invalid load detected

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