error 25

Ok, you'll need the service tool to explore deeper. 25 is a communications error between one board and the rest of the boards. Get into the Technical Alarm Log, and the number after the error points to the suspect board. There's too many to list here in this message. Report back with the ID # and we'll go from there. 

As with most issues on these devices it seems, you just have to swap parts until the problem is resolved.  The service manual suggests the following order: 

I would personally start with the easier to swap components in the pneumatic section.

Depending on ID #. If repeated, replace parts as follows: 0

: Report to MCC HSC for further information.

1: PC 1772 Monitoring.

2: PC 1775 Plug-and-play back-plane.

3: PC 1778 DC/DC & Standard Connectors.

4: PC 1781 Inspiratory pressure transducer. 5: PC 1781 Expiratory pressure transducer.

6: O2 cell or O2 cell cable or PC 1772 Monitoring.

32: PC 1784 Expiratory channel or PC 1772 Monitoring.

33: Gas module Air or PC 1772 Monitoring.

34: Gas module O2 or PC 1772 Monitoring.

35: PC 1772 Monitoring.

256: PC 1771 Control.

512: PC 1777 Panel. 784: N/A

That is a commincation error between the Monitoring PCB 1772 and everything else in the ventilator. This could be a hardware or software failure. The first thing you should do is reinstall the SW software because the software may be corrupt. The SW (service software) is only available to Maquet field service or to people that have attended their training school and bought it. You can also use the SW software to troubleshoot, if that does not fix it, as you randomly swap every board to identify which one is not communicating. This is not an easy problem to trouble shoot. FYI: The user display and lower pneumatic unit have to match ID. If you swap a display, you will need to reload the SW software.