Bosch Washer Er:04, the Control Board Cannot Drive the Door Lock

What Er:04 means

A washer showing Er:04 has a door that may look fine, yet the control cannot operate the lock correctly. Bosch's two service documents point at one part: the triac, a switch on the control module that powers the lock. One calls it a failing triac or module, the other a bad triac or a stuck door relay. For the Vision series the documented remedy is replacing the control.

Common causes of Er:04

Triac on the control module burned out
Door relay stuck on the board
Control module problem affecting the lock output

✓ One safe check you can try

1. Turn the washer off at the breaker and leave it for ten minutes. 2. Switch the breaker back on and start a short cycle. 3. If the code appears again immediately, stop. A reset is worth a single try because a stuck output can sometimes release, but it will not repair a part that has failed on the board.

! Why to stop there

The control module carries line voltage, and opening the console while it is connected risks a shock.
Replacing the lock when the real problem is the triac sends you home with a new part and the same code.
Board repairs involve static-sensitive parts, so poking at them with the wrong tools can end in a full module replacement.

Opening a panel yourself does not automatically cancel a manufacturer warranty, but it can cause accidental damage, and some manufacturers set their own service conditions. Check your warranty terms, or ask us, before deciding.

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Er:04Er:04 questions

Is a reset likely to clear Er:04?

Rarely, but it costs nothing. If the output was only stuck, a ten-minute power-off can release it. When the code returns right away, the board part has failed and needs to be replaced.

Does the control board have to be replaced?

Bosch's own Vision manual lists replacing the control as the remedy. On some models a smaller board-level repair is possible, which we confirm after testing the lock circuit.

Is it safe to use the washer in the meantime?

Without a working lock output the machine will not start properly, so there is little to use. Leave it unplugged if it behaves oddly or smells hot.