Bosch Washing Machine E04 error code

E04 means the AquaStop anti-flood system detected water in the base pan. The washer thinks it is leaking, so it runs the drain pump and blocks the cycle.

Also shown as: E04, E:04, E4, F04

Last updated: October 6, 2026

Quick answer: Bosch washing machine error code E04: leak detected (AquaStop). The most common cause is water leaking into the base pan from a hose or seal. Try this first — unplug and check for visible leaks. If that does not clear it, cut back on detergent.

What causes the E04 error?

  • Water leaking into the base pan from a hose or seal
  • Over-sudsing lifting water into the base area
  • Failed float switch stuck in the tripped position
  • Leaking inlet valve dripping into the base
  • Cracked sump or pump housing
  • Washer not level, pooling water at the sensor

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. Unplug and check for visible leaks
    Unplug the washer. Look around and under it for water on the floor, and check the inlet hoses at the back for drips. Dry up any standing water.
    Safety warning: Do not run the washer while water is pooled underneath it.
  2. Cut back on detergent
    Too much detergent or non-HE detergent creates excess suds that can trigger the flood sensor. Run the next loads with the correct measured dose of HE detergent.
  3. Tilt check for base water (technician)
    A technician can safely tilt the washer to drain the base pan and find the leak source — usually a hose clamp, the door seal, or the pump. The leak must be fixed or E04 will return.
    Safety warning: Do not tilt a full washer yourself. Water and the concrete counterweights make it very heavy.
  4. Reset after the base is dry
    Once the base pan is dry and the leak is fixed, plug the washer back in. The code clears when the float drops.

When to call a technician

Stop and call a qualified technician if any of these apply:
  • E04 returns after drying the base
  • You find active dripping from hoses, the seal, or the pump
  • The float switch is stuck or broken
  • The washer is under warranty

Frequently asked questions

The washer keeps pumping but will not start. Is that E04?

Yes. When the flood sensor trips, the washer runs the drain pump continuously as a safety response and refuses to fill.

I do not see any leak. Why E04?

Small drips collect in the hidden base pan where you cannot see them. Even a slow inlet-valve drip can trip the sensor over a few cycles.

Can too much detergent really cause a leak code?

Yes. Excess suds push water where it should not go, including down into the base pan past seals.

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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