Sounds like you have the sense wire swapped with the ground wire on the Oil Pressure connector or at the GEA 24 -OR- you have the Vsup wired to a +12V output instead of a +5V output (J243 - Pin 18 instead of Pin 19). Check the voltage at the Oil Pressure connector.
Here's the pin-out for the SENSATA/KAVLICO sensors.
Pin A - GND (Black wire)
Pin B - Vsup (Red wire)
Pin C - Vout (Green wire)
Retired Firmware Guy and Airplane Builder
2020 RV-14 QB -- Under construction - Tailcone & Empennage Complete.
2018 RV-7 QB -- Built, Flying
2007 RV-7 QB -- Built, Drowned, Resurrected and flying
1998 RV-8 QB -- Started, Sold
1986 Mooney 205SE
1980 Mooney 231
Aided and abetted building a number of other RV's.