First version

An error code is the bike telling you which part it can't talk to or doesn't trust. Most codes point to a loose plug, a sensor or the battery, and the code list for your system is the fastest way to know which.

First, find out which system you have

The code only means something next to the right list. The motor brand is usually printed on the motor housing or shown on the display at start-up: Bosch, Shimano, Bafang, Brose, Yamaha, or a house brand on many direct-to-consumer bikes.

Write the code down exactly, including letters, before you turn anything off.

Safe things to try

• Turn the bike off, take the battery out, wait a minute, put it back until it clicks, and turn it on again.
• Charge the battery fully. Some codes are just low voltage.
• With the bike off, look over the cables from the handlebar to the motor. Check for plugs that have pulled apart, pinched cables at the steering, or a cable rubbing on the tire.
• Check that the speed sensor magnet on the wheel is still there and lines up with the sensor.
• Make sure no brake lever is stuck partly pulled. Many bikes cut the motor while a brake is on.

Stop and get help if

• The code comes back after a restart and a full charge.
• You see signs of water inside the display, motor or battery plug.
• The code points at the battery or the motor's internals, or the bike gets hot.
• The fix needs a diagnostic tool or a firmware update. Bosch, Shimano and Specialized systems need dealer software for some repairs.

Official sources

• Bosch eBike manuals and downloads
• Shimano e-bike systems FAQ
• Bafang FAQ and error codes