I could not find this information on the web anywhere, so I’m posting it here in case it is useful to someone. (Disclaimer: This worked for me and many others — some slight variants are posted in comments, which you might try if it doesn’t work for you. No promises, of course.)
My 13-month old Bosch Vision 300 Series Washer displayed error code E:27 (E27). Of course, I was just out of warranty.
This error code is not in the user manual, but some research on line indicates that it is a door latch fault. The problem is that the washer will not operate and the door is latched closed.
You can manually release the latch by removing the lower panel (Torx fasteners, I think) and finding a wire lanyard that releases the latch. However, I had read that there was a diagnostic code that could be used to reset the latch solenoid via the control panel.
There is no service manual available on line, as far as I can tell.
Here is what worked…
1. Set the knob to off.
2. Hold down both the Spin Selector button and the Allergy Rinse button simultaneously.
3. While holding these two buttons down, rotate the knob one click to the left, to the “cold” position.
4. At that point, the display will show a diagnostic code and the unit will enter a self-test mode. In my case, the solenoid latch started clicking repeatedly. I pressed the Spin Selector button once or twice, which resulted in the display of new codes and then the release of the latch.
5. I set the knob back to off, and the washer now appears to be operating.
6. You’re done.