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Error code reference

Bosch Washer Error Code Er:04

Door control broken

Bosch codesBosch washer codes

Door control broken — faulty Triac/control module or oversudsing.

First step from the service manual

Check for oversudsing; if not present, check Triac and control module.

The complete diagnostic procedure includes additional test steps, resistance specifications, wiring diagram references, and component test points.

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What Er:04 means on a Bosch washer

The Er:04 error code on a Bosch washer indicates a door control fault. This code is triggered when the control system detects an issue with the door locking mechanism's electrical circuit, specifically pointing to either a failed Triac component within the control module or a problem with the control module itself. The Triac is a semiconductor switching device responsible for controlling power delivery to the door lock assembly. When it fails, the machine cannot reliably confirm or control the door lock state and will halt operation to prevent unsafe use.

Oversudsing is also a recognized trigger for Er:04 and is typically the first condition to rule out. Excess foam generated by too much detergent or the wrong detergent type can interfere with sensor readings and electrical components, causing the control board to register a door circuit fault even when the hardware is intact. This makes oversudsing the most approachable and lowest-cost cause to investigate before moving on to component-level diagnosis.

If oversudsing is not present, the diagnostic focus shifts to the Triac and the control module. A faulty Triac may show visible burn marks or fail continuity testing. A control module failure can produce the same symptom without any outward physical damage, requiring substitution or bench testing to confirm. Both components are part of the main electronic control assembly, and replacement of either typically resolves the fault if oversudsing has already been eliminated.

Source: manufacturer service documentation.

Common causes of Er:04

  1. 01

    Oversudsing from excess or wrong detergent

    Wiring / connection

    Using too much detergent or a non-HE detergent in a high-efficiency washer generates excess foam that can disrupt sensor and electrical circuit readings. Check the drum for visible suds and run a rinse-only cycle to clear them.

  2. 02

    Faulty Triac in the control module

    Part replacement

    The Triac is a semiconductor switching component that controls power to the door lock circuit. A failed Triac can prevent the door lock from receiving proper control signals, and it may show visible burn damage or fail electrical testing.

  3. 03

    Failed control module

    Part replacement

    The main control board governs all door lock functions, and internal board failure can produce an Er:04 code without any visible damage to the board. This is typically confirmed by substitution after the Triac and wiring have been checked.

  4. 04

    Wiring or connection fault in the door lock circuit

    Wiring / connection

    Loose, corroded, or damaged wiring between the control module and the door lock assembly can interrupt the signal the board uses to verify door status. Inspect harness connectors at both the board and the door lock for damage or poor seating.

  5. 05

    Defective door lock assembly

    Part replacement

    Although Er:04 points primarily to the Triac and control module, a door lock assembly that has failed electrically can place unexpected load on the Triac and contribute to the fault. Test the lock assembly's resistance to confirm it falls within specification.

See the test procedure for each cause

Frequently asked questions about Er:04

What does Er:04 mean on a Bosch washer?
Er:04 on a Bosch washer indicates a door control fault. The error points to a problem with the Triac semiconductor component, the control module, or oversudsing that is disrupting the door lock circuit. The washer stops operation when this code appears to prevent running with an improperly controlled door lock.
Can I fix the Er:04 error myself without calling a technician?
If oversudsing is the cause, you can resolve it yourself by running a rinse cycle, reducing detergent use going forward, and switching to an HE-rated detergent. If the fault persists after ruling out oversudsing, the Triac or control module will need inspection and possible replacement, which typically requires disassembly of the machine and comfort working with electronic components.
Is it safe to use my Bosch washer while it is showing Er:04?
No. The Er:04 code signals that the washer cannot reliably control or verify the door lock, and the machine is designed to halt operation when this fault is present. Running a washer with a compromised door lock circuit creates a risk of the door opening during a cycle, which could cause water damage or injury.
How much does it cost to repair a Bosch washer with an Er:04 error?
If oversudsing is the cause, there is no parts cost involved. Triac repair or control module replacement typically involves parts costs ranging from roughly $50 to $300 or more depending on the specific board, plus labor if a technician performs the work. Getting a diagnostic visit from a qualified repair technician will give you a more accurate estimate for your specific model.
Will resetting my Bosch washer clear the Er:04 error code?
A reset may temporarily clear the code, but it will return if the underlying fault has not been corrected. If oversudsing caused the error, clearing the suds and allowing the machine to reset may resolve it for good. If the Triac or control module is faulty, the error will reappear as soon as the machine attempts to operate the door lock circuit again.

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