Workhorse 8.1L Low Oil Pressure

Thanks for all of the info, I failed to mention that I smell oil when this occurs, the engine is very sluggish when pulling the hill and the warning comes up for several seconds and then goes off by itself. Both the oil and filter were changed at the dealer during normal maintenance and the used an AC Delco filter. The oil level is full and appears clean. I haven’t changed the oil sender unit, but the oil smell (nothing visual) makes me think it is more serious.