Mustang GT V8-4.6L SOHC VIN X (1998)
Trunk/Liftgate Sensor/Switch (For Alarm): Testing and Inspection
Measure the installed switch resistance using Rotunda 73 Digital Multimeter 105-R0051 or equivalent. The resistance should be more than 25,000 ohms.
If not, replace the luggage compartment lock cylinder switch.