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E 21020E | Support problems

Usual things

The error can have various causes:

  • Moisture where there shouldn't be any, e.g. after driving in the rain or washing too intensively.
  • Short circuit in the system: e.g. cable jammed or crushed in the head tube/steering head; headlight
  • Motor controller or motor

Test the following

  • Disconnect the motor cable on the left chain stay from the bike electrics. Then go to the service menu and press 'Boost'. If the error no longer occurs, the motor is defective.
  • Disconnect the three motor cables. On almost all models, the downtube cover must be removed. Go back to the service menu and press 'Boost'. If the error persists, the controller (MCU) is defective.
  • If the previous points do not provide a clear answer, it could be the cable between the motor and controller (MCU). This is located in the frame in the bottom bracket area

Solutions

Motor plug: Check the screw connection(s) in the left chain stay for looseness and moisture (blow out with air, allow to dry)

Motor cable routing in the bottom bracket area: On older models, the connections of the 3 motor cables were not protected with shrink tubing. They were therefore susceptible to moisture entering the bottom bracket area via the horn opening when riding in the rain.

Checks / Tests: The Stromer components can be tested with the SIT Test (Test Runner).

> SIT (Test Runner) - Testing components
> Battery SELF_CHECK - Recognize problems

Updated on July 14, 2025
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