Bosch Dishwasher E12 Code: Limescale in the Heat Pump
Updated
Short answer
What E12 means
In Bosch's words, condensed: there is limescale build-up in the heat pump, and the dishwasher needs to be descaled (Bosch).
What Bosch says to try
- Descale the dishwasher; Bosch sells its own descaler.
- If your dishwasher has a water softener function, use softening salt to prevent it coming back.
Unplug the appliance or switch off its breaker before reaching into any part of it. Codes and steps vary by model, so check your manual too.
If the code comes back
Bosch says limescale builds quickly in hard water areas, so regular descaling is the prevention. Usually a descaling, not a repair. A dishwasher heating element, if damaged, runs $150 to $300. (Angi, dishwasher repair cost (updated Apr 6, 2026))
This code is a direct hard-water effect. Water across Winnebago and Boone counties is very hard; see your town's number in the hardness table and what it does to appliances in hard water and appliances.
Related
All Bosch codes on one page: Bosch appliance repair. The appliance: dishwasher repair. This site is independent and not affiliated with or authorized by Bosch; if the appliance is under warranty, contact Bosch first.
Quick answers
What does E12 mean on a Bosch dishwasher?
Bosch says it means there is limescale build-up in the heat pump, and the dishwasher needs to be descaled.
How do I clear E12?
Bosch's steps: Descale the dishwasher; Bosch sells its own descaler. If your dishwasher has a water softener function, use softening salt to prevent it coming back.
What does it cost if E12 keeps coming back?
Bosch says limescale builds quickly in hard water areas, so regular descaling is the prevention. Usually a descaling, not a repair. A dishwasher heating element, if damaged, runs $150 to $300.
Rather have someone fix it?
Tell us the appliance, the brand, the model number and what it is doing. A local technician calls back with a time and a price before any work starts.