P0340 Fault Diagnosis and Fix for 2002 Ford Windstar - Camshaft Position Sensor Circuit Malfunction

I own a 2002 Ford Windstar and recently encountered a P034-0 diagnostic code indicating a 'Camshaft Position Sensor Circuit Malfunction'. Before this issue, the vehicle would frequently stall and required repeated restarts to regain operation. On the morning of the check engine light activation, I drove approximately one mile from home to work at a stoplight. During acceleration, the engine dropped in RPM and then recovered when I released the gas pedal—this behavior was normal until about two miles from work on the freeway. At that point, the vehicle exhibited difficulty shifting gears; it would accelerate, then rapidly drop back down, creating a sensation of not being able to maintain gear. After exiting the freeway and coming to a stop at a traffic light, the engine ran roughly but did not stall. I made it to work and parked for about five hours before driving to lunch. During that trip, the vehicle ran roughly again with intermittent high-pitched squealing. Later, while running errands, the roughness persisted along with occasional squeals. After completing one errand, the car stalled at a light when attempting to accelerate—restarted twice, but each time it made a squeal before dying. On subsequent driving, the squeal continued intermittently until I reached 45 mph on the highway, where it became persistent and only stopped when I reduced speed below that threshold. I checked transmission fluid levels and found them within acceptable range. To avoid repair shop costs—where technicians have previously only replaced fouled spark plugs without identifying root causes—I attempted a DIY fix. My question: What are the most likely causes of P0340 in a 2002 Ford Windstar? Could it be related to the camshaft synchronizer housing, which contains the sensor? Is the intermittent squeal originating from the synchronizer or another component? How can I diagnose and repair this without professional help?