I had a somewhat similar problem on a grand Cherokee where the oil pressure sending unit was shorting out as it shared the same 5v reference circuit with app, tp, and crankshaft sensors and would set codes for all three had to replace it with oem sensor and solved my particular problem. Would have to look at wiring diagram to see on the liberty if this would be possibility for you..

Randy Matthews
Technician
Danny Matthews Garage
Rainsville, Alabama, USA