oil pump weak or bad

most probably a weak pump or system has issues

Have the actual oil pressure tested with a manual test kit... Possible failing oil pressure switch .. Also possible worn crank bearings... Test will reveal culprit.

Agree with other replies, but with a few questions to add to the guesswork puzzle; how many miles on the engine, and what is the idle specification on the under hood emission sticker? 550 sounds kinda low to me, even if it is in drive. Low idle combined with sludged up oil pick-up screen?