Miele Dishwasher Error Code F42 — Mains Frequency Out of Range
What this means
Error F42 indicates the power supply frequency is not 50 Hz or 60 Hz as expected. Miele dishwashers monitor the AC frequency for proper motor speed control and timing. Unstable power from a generator, a failing inverter, or severe grid instability can trigger this. In rare cases, internal control board faults can cause incorrect frequency detection.
Alternate codes: F 42
Step-by-step fix
4 stepsCheck the power supply
Measure the AC frequency at the outlet with a multimeter set to Hz. It should read 60.0 Hz (North America) or 50.0 Hz (Europe/most other regions). Anything outside 59–61 Hz or 49–51 Hz is abnormal.
If powered by a generator or UPS, the frequency may fluctuate — connect directly to the utility grid instead.
Check for shared circuit issues
Heavy inductive loads on the same circuit (large motors, compressors) can cause momentary frequency disturbances. Try running the dishwasher on a dedicated circuit.
Solar inverters and battery backup systems can sometimes output imperfect sine waves that confuse the frequency detection.
Power-cycle and retry
Turn off power for 5 minutes, then power back on and start a cycle. If the frequency disturbance was temporary, the code should not return.
If F42 only appears during storms or high-demand periods on the power grid, it is likely an external power quality issue.
Inspect the control board
If the power supply measures normal but F42 persists, the frequency detection circuit on the control board may be faulty. This requires professional board diagnosis.
A power line conditioner or surge protector with frequency regulation may help if the utility supply is marginally unstable.
When to call a professional
If the AC frequency measures normal at the outlet but F42 persists, the control board's frequency sensing circuit has likely failed and the board needs replacement.
Information compiled from manufacturer service manuals, official troubleshooting documentation, and appliance repair industry resources. This guide is for informational purposes only — always consult a qualified technician for complex repairs.
Learn more about our sourcesParts you may need
Main Control Board (ELP)
Part #Model-specific · $200–$500
If frequency detection circuit is faulty
Links may earn us a commission at no extra cost to you. We only recommend parts relevant to this repair.