As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
During climb out from SGF. The left oil pressure gauge dropped to zero then fluctuated between zero and five PSI. The crew performed the emergency shut dowm check list, declared an emergency. The crew returned the aircraft to SGF. and landed with out incident. After checking the connection on the cannon plug and reinstalling the plug the system checked good IAW. The Fokker Maintenance Manual Chapter 77.