Water Level / Pressure Sensor Fault
The F86 error code means the water level sensor (pressure switch) in your Miele dishwasher is sending incorrect or out-of-range readings to the control board. This sensor monitors the water height in the tub — if its readings are unreliable, the board cannot manage fill and drain cycles safely.
~30%
DIY Fixable
$150-350
Typical Repair Cost
45 min – 1.5 hrs
Pro Repair Time
Quick Assessment
Answer to continue safely
Is it safe to keep using?
No. An unreliable water level sensor can cause overfilling (flood risk) or underfilling (pump damage). Do not use the dishwasher until F86 is resolved.
Can I reset the code?
Yes. Yes. Turn off at mains for 10 minutes with the tub empty. If the pressure tube was temporarily blocked, cleaning and resetting may fix it.
When to stop immediately?
Stop if you notice: The machine overfills noticeably, Water leaks onto the floor during a cycle.
Symptoms You May Notice
Incorrect water level in the tub
The machine may overfill or underfill because the board is getting wrong level data
Machine does not start draining
If the sensor reports the tub as empty when it is not, the drain cycle may not activate
Cycle stops at unexpected points
The board pauses the cycle when water level readings do not match expectations
F86 may appear intermittently
A failing sensor often gives erratic readings — correct on some cycles, wrong on others
Possible Causes
Blocked Pressure Chamber or Tube
The small air tube connecting the tub to the pressure switch is blocked by food debris, grease, or mineral deposits. This is the most common cause (~40%).
DIY PossibleFailed Pressure Switch
The pressure switch (analog or electronic) has drifted out of calibration or failed.
Requires ProfessionalCracked or Disconnected Air Tube
The rubber tube from the tub to the pressure switch has cracked, slipped off, or developed a pinhole leak.
Requires ProfessionalSump Blockage
Debris in the sump area prevents water from reaching the pressure chamber, giving false low readings.
DIY PossibleControl Board Input Fault
The input circuit on the PCB that reads the pressure switch signal has failed.
Requires ProfessionalSafe Checks You Can Do
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1
Clean the Filters and Sump
Remove and clean all filters. Clear any debris from the sump area — a blocked sump can prevent water from reaching the pressure sensor.
A clean sump ensures accurate pressure readings at the sensor.
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2
Run a Hot Empty Cycle
Run the hottest cycle empty with a dishwasher cleaner. This can dissolve grease and deposits in the pressure chamber and air tube.
Add 2 cups of white vinegar to the bottom of an empty tub before starting.
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3
Power Reset
Turn off at mains for 10 minutes. The pressure sensor may need to recalibrate to the ambient (empty tub) pressure.
Make sure the tub is empty before resetting — the board uses the initial reading as a baseline.
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4
Check for Standing Water
Before starting a cycle, open the door and check if any water is sitting in the tub from a previous incomplete cycle. If so, run a drain-only program first.
Residual water throws off the initial pressure reading and can cause F86.
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5
Monitor Fill and Drain Behavior
Start a cycle and observe: does the machine fill to the correct level? Does it drain completely? Note any inconsistencies for a technician.
If the machine alternates between overfill and underfill, the pressure sensor is likely failing.
When to Call a Professional
Contact a qualified Miele technician if:
- F86 persists after sump cleaning and pressure tube inspection
- The water level is consistently wrong despite a clean system
- The pressure switch does not respond to manual testing
- The air tube is cracked, disconnected, or blocked deep inside
- The machine is under warranty
Need Professional Help?
Find qualified Miele technicians in your area for proper diagnostics and repair.
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