Similar chart here with links to the pinpoint tests. https://charm.li/Ford/1989/F 150 4WD Pickup L6-300 4.9L/Repair and Diagnosis/A L L Diagnostic Trouble Codes ( DTC )/Testing and Inspection/Manufacturer Code Charts/ very strange though. Double check with a friend to count the flashes again, and see if the codes come up the same as you initially observed.
Detailed repair manual for the 1989 Ford F 150 4WD Pickup L6-300 4.9L.