1999 Ford F-150 90,000 miles 5.4 Triton V8

My f-150 has been trouble free since I purchased it used 6 years ago. Recently the oil pressure gauge intermittently indicates 0 pressure for several minutes, then will return to normal. The oil/coolant light also is illuminated. I have checked both oil and coolant levels and they are within limits. I assume it is an oil pressure sensor or sending unit problem because of the above oil pressure gauge problem. My check engine soon light illuminated for several days, but has now gone away. I understand by searching on the internet that ford doesn't have a "key sequence" for checking general OBT codes like other manufactures have.