If you want him to stop completely, then you must control the peeing. If he can get far away enough from it, he will pee in the pen. Keep him in the crate when you are gone. When you're home, he's out of the crate, but with you on the leash attached to you going everywhere you go. You must remember that for some dogs peeing a little bit away from their den is far enough, some dogs want to be a long ways away from the den, and then some dogs need to learn what's the right distance for you (meaning outside). Allowing him the freedom of the pen and allowing him to pee there freely is like saying you're ok with it. And you must be consistent. Every day the same way, never get complacent and just put him in the pen for a break.

You also must completely remove the scent of the urine, and for that I always recommend Simple Solution or Nature's Miracle. Follow the directions on the bottle and they both work wonders.

Of course if you live in a house that you own, do what we did and install a pet door. Best $ we ever spent!
Don't forget to praise that pupster like crazy when he pees outside! My neighbors must have thought I was nuts when I praised Chester!

Good luck!