[StefVan]

When you say "disconnected the E-DIFF", what did you disconnect exactly? To really eliminate the E-DIFF you have to disconnect both hoses from the quick couplings. A lot F430s start to suffer from internal differential leaks. If after disconnecting the E-DIFF hoses you still have the same pressure drops, then you know for sure that the problem is at the F1 side. Pump cycling every 120secs with engine off is not normal. With engine off, the pressure should hold a very long time, I mean hours.

 

[StefVan]

Does the quantity of total available hydraulic fluid decreases in the reservoir? If not, you definitely would have an internal leak at the actuator allowing the fluid to flow back instantly depressurized as soon as the actuator is operated (failing teflon seals). It can also be a leaking solenoid valve at the Power Unit blocked open causing a big instant drop. EV #1/#3/#5 are all 3 used for N and 1st gear engagements.

 

[StefVan]

Changing the accumulator is a always a good thing to do but will not fix your issue. You have 100% an important internal hydraulic leak you need to fix as the pressure drop happens only when your engine is running. Checking your actuator would be a good start.

Some more useful tips here: Smart eMT F1 Relay ECU - Recommendations - SIS Techno - Scud Ing Swiss

 

[StefVan]

Interesting, thanks for sharing, it looks like you've fixed the first step of your issue as the pressure is now holding up longer (about 5 min?).
Is the "Good accumulator" graph with ignition on only or engine idling, warm or cold?