What Er:04 Means
Er:04 on a Bosch front-load washer means the control cannot drive the door lock correctly. Both service documents name the same component: the triac on the control module that switches the lock, described in one as a faulty triac or control module and in the other as a defective triac or a stuck door relay. The documented remedy in the Vision manual is to replace the control.
Common Causes of Er:04
- Triac on the control module failed
- Door relay stuck on the control board
- Control module fault affecting the lock output
🔧 One Safe Check You Can Try
Cut power at the breaker for ten minutes and restore it, which is worth one attempt because a stuck output can sometimes release. If the code returns immediately, the fault is on the board and no amount of resetting will change that.
⚠ Why You Shouldn't Go Further Than That
- The fault is on the board that switches mains voltage to the lock, which means a component that has failed while carrying line current.
- Bosch distinguishes this from a lock or harness failure, so replacing the lock will not help even though the symptom is about the door.
- The control module in these machines sits behind the fascia, and its connectors carry both mains and low-voltage circuits side by side.
- Boards are model and revision specific, and a fitted one is rarely returnable if it turns out to be wrong.
Opening a panel to inspect or repair something yourself doesn't automatically cancel your manufacturer's warranty — but it can risk accidental damage, and some manufacturers do have specific service conditions. Check your product's warranty terms, or ask us, before deciding.