I have a 2004 3.9 V6 mustang. It had a sqeaking sound. I took it to the shop several times and replaced the belt, tensioner arm, water pump, ac compressor and alternator. The steady squeak is gone, but now it has a loud screeching sound that comes every 5-10 minutes. There is also a Service Engine light on that says something is wrong with the crank sensor. My mechanic says the crank sensor is fine. Any ideas what it could be?