I have two F250s 7.3L diesels for my company, a 2000 and a 2001. The 2001 is making a weird noise when you turn on the accessories but not the engine. There's a component in the front of the engine compartment on the driver's side, as far into this front corner as possible, that makes an "I'm dying" electronic sound. I was told this is a fuel modulator, yet can't find much on the internet when I google "Fuel modulator F250". Can anyone help me to better identify this part (I could snap off a photo after it stops raining outside) and possibly why it makes such a horrible noise. The truck runs fine now, but my other F250 doesn't make this noise and I'm worried this one will die at the least convenient time.

Thanks for your time and help.