Bosch Dishwasher E04 — What It Means & How to Fix It
During its power-on self-test the Bosch dishwasher found a fault in the heating electronics, so it shows E04 and holds back rather than energising the heater — a technician diagnosis after a single reset.
What this code means
E04 is raised by the dishwasher's self-check at the start of a cycle: the control electronics that manage the flow-through heater reported something out of range before washing even began. Because the heater runs on mains voltage and the fault is in its control circuitry, the machine sensibly refuses to power it. This is detection working as intended, not a loading or filter problem.
E04 is tied to the heater self-test on Bosch dishwashers. One power reset rules out a momentary glitch; a repeat means the heating electronics need a technician's meter, not a setting change.
Most likely causes
| Cause | How likely | DIY-fixable? |
|---|---|---|
| Heater control circuitry on the main board failed its self-test | Common | No — technician job |
| Temperature sensor feeding the heater logic is reading out of range | Common | No — technician job |
| The flow-through heater element has gone open or shorted | Occasional | No — technician job |
| Transient electronics glitch at power-on | Less common | Yes — power reset only |
What you can try yourself
- Turn the machine off at the breaker, wait two minutes, and restore power so the self-test runs fresh; a one-off glitch clears here.
- Check that household hot water reaches the kitchen tap, since an unusually cold supply can stress the heating logic on some cycles.
- If E04 shows again at the start of the next cycle, stop and book service, because the heater and its electronics are mains-voltage parts behind the tub.
- Mention to the technician whether dishes have been finishing cold and wet, which points at the element rather than the sensor.
When to call a technician
- E04 appears at the start of every cycle even after a reset.
- Dishes come out cold and dripping, suggesting the element is not firing.
- The breaker trips or there is a hot-electronics smell when the cycle begins.
Typical professional repair cost: Diagnosis runs $90–$160; replacing the heating element/pump assembly or the control board commonly lands between $200 and $450 with labor.
Frequently asked questions
Why does Bosch E04 appear before the cycle even heats?
The dishwasher runs a self-test at power-on, and E04 means the heater electronics failed that check before washing started. The machine blocks the cycle rather than energise a circuit it cannot trust.
Is E04 the same as the E09 heating fault?
They are related but not identical. E09 flags the heat pump's internal heater during operation, while E04 is the self-test catching a heater-electronics fault up front. Both end up as technician repairs because of the mains-voltage heater.
Can I keep using the dishwasher with E04?
It is best not to. Even if a cycle limps through you will get poor drying, and you would be running a machine that has already flagged a heating-circuit fault. Wait for the repair.
Related Bosch codes
- Bosch Dishwasher E15 Water reached the base pan under the tub and Bosch's leak protection locked the machine — sometimes a genuine leak, often a one-off spill or condensation that clears once the base dries.
- Bosch Dishwasher E24 The dishwasher can't drain properly — start with the filter, then the drain hose path, and don't skip checking that the drain pump cover is seated.
- Bosch Dishwasher E25 The drain pump itself is blocked or its cover is loose — and Bosch makes the pump cover owner-accessible, so this is one of the most fixable codes the brand throws.
- Bosch Dishwasher E09 The heating system isn't raising the water temperature — beyond one reset, the flow-through heater is a mains-voltage part that belongs to a technician.
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