Sounds like something I'm chasing. Aside from the high pitch noise...
I too have had the SES light pop up on several occassions. First off
you need to get your code scanned. Over here, Autozone will do this
First time the SES light fired (P0303 engine misfire - cyl #3)... fuel
injector #3 had to be replaced. This was *after*
I had already
replaced the plugs, wires and coil pack. My guess is that none of the
electrical parts needed to be replaced.
Second time my '97 Escort started running like crap (no SES light this
time) I could clearly hear a vacuum leak under the hood. I had to
replace the 90 degree rubber elbow that feeds into the line for the PCV
valve. Car ran like a champ (very smooth) after that.
Now, again I'm chasing down a SES light. This one is troubling since
after diagnosing the P0301 code I was convinced it was another
bad/clogged injector. My car also has nearly 130k on it. I replaced
injector #1 as well as the plugs. I also tested the coil pack and just
recently replaced the wires. Now... I'm getting 2 (!) codes firing,
P0301 and P0303. I ended up dropping off the car to a trusted mechanic
as I'm done trying the shotgun approach.
I hope you have better luck than me.