89 C1500. Dash idiot lights

When the ignition is on, before starting, only the "Check gages" and the battery warning lights are lit up. Surely this is wrong. Shouldn't the oil warning light (by the 0 on my oil pressure gage) light up too? When I first got this truck, I took the instrument panel to a shop who checked it out and either said everything was working or fixed things so that everything ws working. I cannot remember now if, at that time, other warning lights lit up. Anyone know how to troubleshoot? Thanks, David