Dishwasher
E12
The E12 error code on a Miele dishwasher indicates a limescale or soiling build-up in the heating circuit — specifically on the flow heater. It’s a moderate fault that will stop your machine cleaning properly, but in most cases it’s fixable without a call-out.
What does this error mean?
Miele’s E12 code means the dishwasher’s internal sensors have detected that the flow heater (the component that heats water as it circulates) is heavily scaled or fouled. This reduces heating efficiency and triggers a protective shutdown. If ignored, it can cause the heater element to burn out permanently, turning a cheap fix into an expensive one.
Est. repair cost
£0–£20 DIY descaler fix; £120–£200 for professional flow heater or sensor replacement
🔍 Likely causes
🛠️ Step-by-step fix
Run a dedicated dishwasher descaler cycle: use a purpose-made product such as Miele’s own descaler (or a reputable alternative like Finish Dishwasher Cleaner). Add it to the base of an empty machine and run the longest, hottest programme available (typically 65–70°C).
Check and top up the dishwasher salt reservoir, found at the base of the wash cabinet. If the salt indicator light has been on for some time, the internal water softener may be saturated with limescale — top up the salt and run two back-to-back descaler cycles.
Clean the filters: remove the coarse and fine filters at the bottom of the dishwasher, rinse them under the tap, and scrub gently with a soft brush. A blocked filter restricts flow and worsens scale deposits on the heater.
Reset the machine after descaling: switch the dishwasher off at the mains, wait 30 seconds, then power it back on. Run a short hot cycle to see if the E12 clears.
If the E12 error persists after two descaler cycles and a full reset, the flow heater or NTC sensor likely needs physical inspection or replacement — do not attempt to dismantle the heating assembly yourself, as this involves draining and accessing sealed electrical components. Book a Miele-approved or qualified appliance engineer.
📞 When to call a professional
If the E12 code returns after completing two full descaler cycles, refilling salt, and resetting the machine, the flow heater element or temperature sensor has likely failed and needs replacing. Call a Miele-approved service engineer or a qualified appliance repairer and tell them: ‘My Miele dishwasher is showing error code E12 — I’ve descaled it twice and it hasn’t cleared.’ Do not continue running the machine, as a failed heater can cause further damage to the control board.
⚖️ Repair or replace?
A professional repair — typically replacing the flow heater or NTC sensor — costs around £120–£200 including parts and labour in the UK. Miele dishwashers are built to last 15–20 years, so if your machine is under 10 years old, repair is almost always the better financial decision. If it’s over 12 years old and has had previous faults, compare the repair quote against a new mid-range Miele (£699–£900) before committing.