just had oil changed at dealer on 06 monte carlo. 177k, within a week low engine pressure/stop engine light and oil car light up while on highway. since it just came back, oil isn't low.. first time this has happened ever...no other engine symptoms.. power, fine, no knocks, no temp rise, no smells.. could they have put the wrong oil filter on? oil sending switch? oil pressure sensor?

 

if the oil level is ok, the engine is not knocking then the oil sending unit is probably nfg. Its 11yo...t.hey can fail

 

See if you can get a code thru the OBD with a scan tool.