Onan false low oil pressure shut down

My 7.5 HDKAJ1145C Ser#C973658705 shuts down after 13 seconds and fashs
a code 2 (low oil pressure). This has been an intermittent problem.
It has a Spec F inverter installed approx 3 years ago by a factory
technician due to corrsion on the plug pins because the factory failed
to apply diaelectric grease during assembly. I changed the oil
pressure switch on the engine. The generator acts the same. I have 25
hours of intermittent use since changing the switch. The generator may
run 20 min, 3 hours, or 13 sec. I believe the problem is a false low
oil pressure shut down caused by a bad circuit board
*300-5030-----CS-0102800128* in the inverter. Maybe a cold soider
joint or faulty component. I would like a circuit diagram of this board
so I can trace the low oil pressure circuit and look for the problem.
I'm trying to avoid spending another $1000.00 plus on a replacement
inverter. The board does not appear to be available for purchase
without buying the whole inverter? Please help.