94 Chevy z71 check gages light

I have a 94 Silverado Z71 with a 5.7 v8 and 187,000 miles on it the engine has less than 70,000.The check gages light wont go off,oil press. is 40psi,temp is 180, Volt is 13.0 and yes the gas is full.I pulled the oil sending unit and used a mech. gauge and it reads the same as the dash.And the computer shows no stored codes.The light came on and stayed once before a few months ago but went off by itself Truck runs fine , power is good, everything works but the light is driving me nuts