Like onetonford said they are usually very close to the water heater. Most of the time the WH and by are not in the most user friendly spot to get to and may sometimes hidden. On our TT it was under the bed in the "master bedroom", I almost have to crawl into the compartment under the bed to get to it. On our old TT it was under the sofa, I could see it and I could reach it, but I just couldn't do both at they same time where it was placed. Good luck!!
TT-2013 Passport 3220BH
TV-2004 F150 FX4, not exactly stock...
with 2001 Kodiak K215: 2010-10, 2011-12
with 2012 Grey Wolf 26BH: 2012-19, 2013-24, 2014-11, 2015-6
with 2013 Passport: 2015-13, 2016-15 booked