2003 SL500 R230 42,500 miles

I'm at wits end and no garages around who know the system well, i know more then them and that's not saying much
Cant afford to start throwing parts until something fixes it. Def cant afford to go to the MB Dealer.

Red ABC warning light comes on Drive careful

With iCarsoft MB v3.0 scan fault code low pressure 0 BAR i can clear it , comes back on start up , clear it again, comes back on start up .

I can let the car sit for for 24-48 hrs and it starts up like brand new, NO red light 190 BAR pressure is great.mmWill drive 1-50 miles runs great until i shut it down then comes back.

1) Fluids checked both running and not correct levels.
2) No leaks
3) No hard hits like from a bad actuator
4) Took a look at the pressure sensor left front wheel behind the wheel well splash shield pulled the wire clip, wires appeared not frayed , connector was not corroded.
5) When working properly I can go through up / down all 3 heights and pressure doesn't go below 170 bar
6) No other fault codes

I feel the pump is good otherwise wouldn't get the 190 BAR when red light is not on . something causing the pump to go to zero or just not reading the true pressure and locking the system up

I'm at a LOSS ????