Diagnostic Aids
WARNING: This page is about a different car, the 1995 Chevrolet Corvette. However, it is still accessible from the selected car via links, so may be relevant.
An intermittent may be caused by a poor connection, mis-routed harness, rubbed through wire insulation or a broken wire inside insulation. Code 48 could be caused by a vacuum leak. Check short and long term fuel trim for being in optimum range (both banks).