Welcome to JOF. Just take a peek under its belly for tubes - if you find others and if there's no valve, look in the space above them for a panel to gain access. Mine has a panel on a vertical wall in the basement that when removed, let's mt open the low point drains.
2014 Eagle Premier 331RETS
2016 Silverado 3500 DuraMax/Allison
1975 Corvette & a couple ATV's