Why is my amp gong into protection mode?

Why is my amp gong into protection mode, Its brand new 1600watt 2 channle Boss GT 1800 right out of the box. I have 2 12'inc pioneer TS-W301R 800watt MAX 150watt RMS right out of the box. When I turn everything on at a low lev, its fine but when I turn it up it gose into protection mode. Its not over heating, I went from a 4 gauge ground to 8, Took the paint off were its grounded, new fuse, Tuned it right EVERY THING!!! If you know whats wrong or have ay suggestions please let me know its driving me freaking crazy!

how do you have the subs wired. and you said you went from 4 guage wire to 8 guage wire for the amp?

I have the 12's briged, yea went from a 4 to an 8 gauge for the groud. And I had it running for a while and the amp is getting hot and goes into protection mode. If I were to get a cap would that not happen?

you're load on the amp is too low ...... that amp is only 2 ohm stable (4 ohms bridged), you have 2 4 ohms subs in parallel - making a 2 ohm load on the amp. It's not too bad at low volume, but the impedances can vary quite a bit when the sub starts moving a lot.