Bosch Dishwasher E04 error code

E04 means the dishwasher's self-test found faulty heater electronics. The control ran its internal check on the heating circuit and it failed.

Also shown as: E04, E:04, E 04

Last updated: October 6, 2026

Quick answer: Bosch dishwasher error code E04: heater electronics self-test fault. The most common cause is failed heater electronics on the control module. Try this first — reset power at the breaker. If that does not clear it, clean the spray arms.

What causes the E04 error?

  • Failed heater electronics on the control module
  • Heavy limescale on the heat pump insulating it
  • Clogged spray arms reducing water flow past the heater
  • Power surge damaging the heater circuit
  • Failing flow sensor confusing the self-test
  • Worn circulation pump straining the heater circuit

How to fix Bosch E04 — step by step

Work through these in order, from simplest and safest first. Stop as soon as the code clears.

  1. Reset power at the breaker
    Turn off the breaker for a few minutes, then restore power. A glitch in the self-test can clear. If E04 returns on the next cycle, the fault is real.
  2. Clean the spray arms
    Remove the upper and lower spray arms and rinse them under running water. Poke out clogged holes with a toothpick. Poor spray flow can make the heater self-test fail.
    Safety warning: Turn off the breaker before removing spray arms.
  3. Descale the dishwasher
    Run the hottest empty cycle with a dishwasher descaler. Limescale on the heat pump is a known trigger — the heater cannot transfer heat through the scale layer.
    Safety warning: Use a descaler made for dishwashers, not harsh acids.
  4. Call Bosch support if it persists
    Bosch's official guidance for E04 is to contact Bosch Customer Support at 1-800-944-2904. Heater electronics faults need professional diagnosis.
    Safety warning: Do not attempt heater circuit repairs yourself.
Related guide: Dishwasher troubleshooting — fix common problems, with links to every dishwasher error code we cover.

When to call a technician

Stop and call a qualified technician if any of these apply:
  • E04 returns after reset, cleaning, and descaling
  • The dishwasher is under warranty
  • You suspect the control module or heat pump
  • There is any sign of water leaking near the electronics

Frequently asked questions

My dishes are not drying and E04 shows. Related?

Yes. The heater handles both wash heating and drying. Faulty heater electronics affect both.

Can limescale really cause an error code?

Yes. Scale insulates the heater so it cannot reach temperature in time, and the self-test flags the circuit as faulty.

Is E04 the same as E09?

No. E04 is the heater electronics failing the internal self-test. E09 is a heating circuit interruption (often the element itself).

Sources

Every meaning and fix above was checked against official manufacturer documentation:

FixCode provides general troubleshooting information only — not professional repair advice. If you are unsure about any step, stop and call a qualified technician. Repairs done incorrectly can be dangerous and may void your warranty.

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