Can a 04durango oil cap cause pressure loss n light to come on

No.
The oil pump in the engine produces the oil flow and the clearances between moving parts in the engine is what creates the "oil pressure" (which is why a worn engine will typically display low oil pressure).

The cap on the oil filler opening is totally irrelevant to the oil pressure being generated in the engine.

If you have low oil pressure you need to have it investigated immediately. Driving the vehicle with low oil pressure will cause engine damage because insufficient lubrication will be getting to all moving parts. If your 2004 engine is not very high mileage, in good condition and if well maintained with adequate oil changes and so on(which most are not) then the problem may be that the oil pressure relief valve is jammed open or the oil pump itself might be failing and is unable to produce sufficient flow volume.

If you have a worn engine, replacing the oil pump will not fix a low oil pressure issue solely caused by excessive clearances between moving parts due to years of normal wear or years of higher wear due to maintenance neglect.