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F21

F21 — Control system malfunction or uneven motor operation

Bosch · Washing Machines

What does F21 mean?

The washing machine's control system is experiencing issues, or the drive motor is not operating correctly, leading to the drum not rotating. This is often due to electrical faults.

Common Causes

  • Short circuit in control electronics (triacs)
  • Faulty tachogenerator
  • Defective reverse relay
  • Motor control issues

Repair Steps & Checklist

Click steps to track your progress.

  1. 1

    The program may be canceled. After several attempts, the machine enters 'IMPORTANT TROUBLE' mode.

  2. 2

    Check for any loose or damaged wiring related to the motor and control board.

  3. 3

    Consider running a test program if available in the manual.

  4. 4

    Contact customer support if the issue persists.

Browse all codes in this manual (47)
Verified technical data. Last updated: April 2026

Related Faults

E02E02 — Motor problemE67E67 — Incorrect module encodingF01F01 — Door not closed or laundry obstructing door
Source: Bosch Washing Machines
Open Manual (Page 2)Search more codes in this manual