mypros+
Error code reference

Miele Washer Error Code F4255

EFU fault low voltage; EFU 235 input voltage <320Veff, phase missing or fuse tripped.

Miele codesMiele washer codes

EFU fault low voltage; EFU 235 input voltage <320Veff, phase missing or fuse tripped.

MyPros+ Max

Get the full diagnostic procedure for F4255.

  • Step-by-step tests with expected resistance, voltage, and continuity values
  • Wiring diagram references and connector pinouts from the OEM service manual
  • Verified part numbers when replacement is required
Get the full procedure

$29/month · Cancel anytime · Or $9.95 3-day pass

What F4255 means on a Miele washer

The F4255 error code on a Miele washer indicates a fault with the EFU (Electronic Frequency Unit or power conditioning module), specifically that the input voltage has dropped below 320 volts effective (Veff) on the 235V input circuit. This code is triggered when the appliance detects that the incoming supply voltage is insufficient for safe and proper operation. The EFU monitors the AC input to ensure stable power delivery to the motor drive and control systems, and when voltage falls below the defined threshold, the unit faults to prevent damage to downstream components.

The most direct causes of this fault are a missing phase in the supply line, a tripped fuse in the electrical supply circuit, or an actual low-voltage condition from the household or building electrical supply. In three-phase installations or certain high-current single-phase setups, a lost phase will immediately drop the effective input voltage well below the 320 Veff threshold. A tripped breaker or blown fuse on the supply side will produce the same result, as the EFU registers the loss of voltage on that leg.

Before assuming the EFU module itself has failed, technicians should thoroughly inspect the incoming power supply: verify fuse continuity, check breaker status, and measure actual line voltage at the terminal block under load conditions. If supply voltage is confirmed within specification and the fault persists, the EFU module may have an internal fault and will require further testing or replacement.

Source: manufacturer service documentation.

Common causes of F4255

  1. 01

    Tripped circuit breaker or blown supply fuse

    Wiring / connection

    A tripped breaker or blown fuse on the circuit feeding the washer will cut voltage below the required 320 Veff threshold. Check the breaker panel and any dedicated fuses on the appliance supply circuit and restore power before testing further.

  2. 02

    Missing or lost phase on supply line

    Wiring / connection

    In installations where a phase is lost due to a wiring fault, loose connection at the terminal block, or utility supply issue, the EFU will detect the drop in effective voltage and trigger F4255. Inspect all supply line connections at the terminal block for corrosion, looseness, or breakage.

  3. 03

    Low voltage from building electrical supply

    Wiring / connection

    If the household supply voltage is consistently below the minimum threshold, possibly due to utility issues or an undersized supply line, the EFU will fault. Measure line voltage under load conditions with a calibrated multimeter to confirm.

  4. 04

    Faulty or damaged supply wiring to the machine

    Part replacement

    Damaged power cord, corroded terminal connections, or loose internal wiring between the supply input and the EFU can cause a voltage drop that triggers this code. Inspect the power cord and all connections for physical damage or heat stress.

  5. 05

    Failed EFU module

    Part replacement

    If all external power supply factors have been confirmed as correct and the fault persists, the EFU module itself may have an internal failure causing it to misread or fail to accept the incoming voltage. Component-level testing or replacement of the EFU would be required.

See the test procedure for each cause

Frequently asked questions about F4255

What does F4255 mean on a Miele washer?
F4255 indicates an EFU (Electronic Frequency Unit) fault caused by low input voltage. Specifically, the washer has detected that the incoming supply voltage has dropped below 320 Veff on the EFU 235 input circuit. This is typically caused by a tripped fuse, a missing phase, or a low-voltage condition in the electrical supply. The machine shuts down to protect its components until the power supply issue is corrected.
Can I fix F4255 on my Miele washer myself?
Some causes of F4255 are DIY-accessible, such as resetting a tripped circuit breaker or replacing a blown supply fuse. However, if the problem involves internal wiring, terminal block connections, or the EFU module itself, a qualified appliance technician should perform the repair. Working with the electrical supply to a large appliance carries serious shock and fire risks if not handled correctly.
Is it safe to keep using my Miele washer when F4255 is showing?
No, you should not attempt to operate the washer while F4255 is active. The error indicates the appliance is not receiving adequate voltage, and running it under these conditions could damage the motor drive, control electronics, or other internal components. Resolve the power supply issue before resuming use.
Will resetting my Miele washer clear the F4255 error?
A simple reset will not permanently clear F4255 if the underlying power supply problem has not been fixed. The EFU continuously monitors incoming voltage, so the fault will return immediately or shortly after restart if the voltage remains below 320 Veff. You must identify and correct the root cause, such as restoring a tripped breaker or repairing a wiring fault, before the error will stay cleared.
How much does it cost to repair a Miele washer F4255 error?
Repair costs depend on the cause. If a tripped breaker or blown fuse is the issue, costs may be minimal, typically in the range of a few dollars for fuse replacement or no cost at all for resetting a breaker. If internal wiring or the EFU module requires replacement, professional repair costs can range from around $150 to over $500 or more depending on parts and labor rates in your area.

Related Miele washer codes

All Miele washer codes
View all 254 Miele washer codes

78,000+ service manuals · 160,000+ error codes · 55+ brands

Get Started

$29/month · Cancel anytime · Or $9.95 3-day pass