Bosch error 0x503002: Speed sensor magnet misplaced or tampered
The drive unit has detected that the spoke magnet is not in the correct position relative to the speed sensor on the chainstay, which the firmware also flags as a possible sign of tuning. Motor support is reduced to a walk-level restriction and the speed reading on the display drops to zero. Walk assist is typically unavailable while the code is active.
| Drive system | Bosch eBike (DiagnosticTool / eBike Flow hex code) |
| Severity | Dealer needed |
| Keep riding? | Do not keep riding |
| Typical cost | Spoke magnet replacement runs roughly 5 to 15 EUR, a speed sensor assembly around 60 to 120 EUR, and a Bosch dealer diagnostic plus labour typically totals 80 to 180 EUR depending on the workshop rate. |
Likely causes
- Aftermarket tuning module fitted to the motor or speed signal
- Spoke magnet slid, twisted, or fallen off the spoke
- Wheel removed and refitted with magnet not aligned to the sensor
- Bent or loose speed sensor bracket after a crash or transport impact
- Damaged or cracked magnet with weak signal
- Corroded sensor connector or pinched cable near the dropout
How to fix Bosch error 0x503002
- Switch the system off and remove the battery before any inspection.
- Locate the small round magnet fitted to a spoke on the rear wheel.
- Slide the magnet along the spoke until it lines up opposite the sensor body on the chainstay, then check it sits centred over the sensor with about 2 mm of air gap.
- Inspect the sensor bracket and cable for damage, and reseat the connector if it has worked loose.
- If a tuning chip or dongle is present anywhere in the system, disconnect it and remove it completely; the bike must run on standard hardware.
- Refit the battery, power the system on, and ride a short distance to see if the code clears on its own.
- Take the bike to an authorised Bosch dealer for a diagnostic readout and authorised clearing if the warning returns after these checks.
Warranty: Tampering-related faults are excluded from warranty; a genuine magnet, sensor, or wiring failure inside the typical two-year Bosch eBike warranty period is usually covered as a manufacturing defect.
Typical cost: Spoke magnet replacement runs roughly 5 to 15 EUR, a speed sensor assembly around 60 to 120 EUR, and a Bosch dealer diagnostic plus labour typically totals 80 to 180 EUR depending on the workshop rate.
Frequently asked
Can I reset bosch error 0x503002?
There is no owner-level reset for this code. Once the magnet is back in position and any tuning hardware is removed, the code usually clears automatically on the next power cycle. If it persists, an authorised Bosch dealer must clear it with the DiagnosticTool.
Is it safe to keep riding with this code active?
No, riding is not recommended. Motor support drops to a minimal level and the speed display reads zero, which leaves you propelling a heavy bike unassisted. Continued riding also does not clear the fault and can mask an underlying sensor problem.
How much will the repair cost and is it under warranty?
A magnet or sensor swap on its own is usually 15 to 140 EUR plus labour. If a tuning module caused the fault, Bosch treats it as out of warranty; a genuine component failure within two years of purchase is normally covered.
Related Bosch codes
Manuals and video
- Bosch eBike Help Center: official error-code index
- Bosch eBike downloads: quick start guides and battery guide
- Bosch eBike dealer search (DiagnosticTool readout)
Official source: www.ridewill.com
Not an official Bosch document. Compiled from workshop experience and public service information; details can differ per system version and bike brand.