Beeping Noise that only stops when the parking brake is applied

Seat belt? On or unplugged?

 

This would be My guess... Seat belt is not buckled... Or on some fleet trucks, a door is not shut tightly.

 

Does the seatbelt light go off?

 

I have the same problem. Taken the truck to the dealer 3 times in the last 5 weeks, it kept getting worse, at 1st it would beeb for 20 seconds. Then anywhere from 2 to 3 minutes. Now its on continuously.
Code 520581-2 is showing as the fault code.

 

Some of these trucks have door plunger switches built into the lower side of the dashboard facing the door if they break it will cause the a constant ding noise

 

Low air or dumped airbags are a continuous buzz.

Door or seatbelt is my guess. The seatbelt switches are prone to fault. You can unplug them near where the seatbelt bolts to the floor.

IIRC, you have to replace the whole seatbelt to replace the switch... If that is the issue.

 

I'm having the same problem on my KW T880. Did your problem get fixed? What was causing it?

 

I unplugged one of two plugs on trucks location system to eliminate a faint continuous beep. The aftermarket tracking unit was under drivers seat