As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
LGA/DCA - FLT 6421 - ON TAKEOFF, THE NR 1 LOW OIL PRESSURE LIGHT ILLUMINATED. FOLLOWED ABNORMAL PROCEDURES, OIL PRESSURE REMAINED NORMAL. REPLACED NR 1 ENGINE OIL FILTER AND NR 1 OIL BYPASS PRESSURE SWITCH. RAN ENGINE NR 1 OIL PRESSURE/BYPASS LIGHT OPERATIONAL CHECK NORMAL. (X)