my car wont start it says oil presure sensor on dash on 1990 BMW 535i

i pulled up at gas station turned car off now it wont start and says oil presure sensor it turns over but wont fire up

Asked by for the 1990 BMW 535i
There is a oil pressure sensor under the right side where you put the water in car its cheap easy to replace.also there is a good chance it could be your fuel pump relay switch or fuel filter or fuel pump but its best to start with the relay switch or filter