Of course, you would never consent to letting them check your trunk, because you wouldn’t give them any reason to ask, right?
If they found drug paraphernalia in your trunk, it may or may not be probable cause for a search of the rest of your car and the people in the car, and if any of you guys have weed on you, then the trouble really happens. If they found the pipe and didn’t want to search you or you car, they would probably confiscate it and run tests, then charge you with some charge, you’ll have to look up your laws in Los Angeles to find out what charge exactly.
Then again the cop could also not give a hoot and let you go on your business. But that’s not a risk I’m willing to take really.