Error codes on e-bikes: the clear guide by brand (Bosch, Shimano, Bafang)

An error code lighting up on an e-bike display is sure to cause panic — and information handled haphazardly across the web: contradictory forum threads, PDFs from 2019, approximate translations. Result: parts get replaced at random. This guide sets a clear foundation: what a code means, the reflexes that unlock the majority of cases, and the reference to the exact list for your brand.

Warning or blocking error?

All systems distinguish between two levels:

• Warning (often a "W" on Shimano, an icon on Bosch): the bike still rides, but something needs attention.
• Blocking error: assistance cuts out. The bike remains usable in pedal-only mode, but the motor won't respond until the cause is resolved.

Knowing which category your code falls into prevents overreacting to a simple warning.

The 5 reflexes that fix most codes

Before any disassembly, in order:

1. Power off then back on (wait 10 seconds with battery off). A restart clears most transient communication errors.
2. Reinsert and lock the battery. A loosely clipped battery or oxidized contact generates power or communication errors.
3. Check connectors: display cable, speed sensor cable, motor cable. A bent pin or moisture is enough.
4. Check charge and temperature. Below 0 °C or above ~40 °C, many systems go into safety mode. Let it return to room temperature.
5. Firmware update at your dealer if the code persists. A large portion of "system" errors resolve with a simple update.

The speed sensor, cause #1 of false alarms

On most e-bikes, the most common error comes from the speed sensor: the magnet fixed to a spoke has shifted, moved away, or budged, and the system no longer reads the wheel. A simple realignment of the magnet facing the sensor (a few millimeters) fixes a large number of codes wrongly blamed on the motor.

The precise list, by brand

Codes don't mean the same thing from one brand to another. Here's where to find yours:

For Yamaha (and Giant bikes with SyncDrive motors) as well as Brose/Specialized, codes are mainly delivered through the manufacturer's app: note the message displayed and check it against official documentation or the mechanic AI.

Temperature: the error that fixes itself by waiting

Many codes indicate no malfunction: the motor or battery are simply too hot (long climb in summer) or too cold (winter ride). Assistance returns on its own once temperature normalizes. Don't replace anything before ruling out this case.

Making the right diagnosis

To maintain the battery at the heart of many of these codes, see extending e-bike battery life and the complete e-bike maintenance calendar. If you're still choosing your e-bike, our 2026 e-bike buying guide compares systems.

Give the exact code and brand to the mechanic AI: it translates the code, rules out false leads, and gives you the first check tailored to your system.