heres some info that might help you better diagnose your radio problem.
Audio System Inspection and Verification
ICP Self-Diagnostic Mode
NOTE: To enter the ICP Self-Diagnostic Mode, the ICP must be ON and in radio tuner mode (AM/FM).
i'm thinking you have a wiring problem, heres 2 wiring diagrams for your radio.
i would check the power and grounds.
hope this helps you
mike
you could install an aftermaket radio, i would still go through the wiring.
see ya
Mercury Technician
over 13 years as a ford,lincoln, mercury technician at a large dealership