Diddy -- Mo' Decibels, Mo' Problems

Diddy's arm and his ass were in a sling Tuesday, after Miami po-po nailed the rapper for blasting music in his tricked out Jeep so crazy loud ... he couldn't hear the cops tell him to turn it down.
Diddy: Click to watch
Miami Beach PD tells us P.D. was rolling in his whip around Miami Beach, music blaring, when a cop pulled up to the car and asked him to turn the music down. When the Bad Boy CEO didn't comply -- or even acknowledge -- Diddy was pulled over and ticketed. The fine will run Diddy about a Benjamin -- good thing he doesn't have to pay Aubrey O'Day anymore.

FYI -- We're told Diddy was "very cooperative."