2013 Sierra Electrical gremlins - no electrical power sometimes, everything electrical starts flashing

[malfar]

Sometimes when  truck is unlocked and I get in and turn the ignition nothing happens - no crank, no lights, no radio - nothing.  if I try it a few times it fires up and dash etc is  normal.  The other day it was locked and the key fob wouldn't unlock it, no lights flashed etc - try a few times and finally worked.  In these instances it's like there is no battery in it.  I changed the battery because I knew it wasn't good.  Day after I put battery in - truck fired right up but dash and radio blinked on and off rapidly for 20 or 30 seconds.  Today fired right up but dash lights all lit up normal, radio, heater etc came on ,  then flashed off,  came back on .   After it does the flashing thing I often get a "Service trailer brakes" error on the dash, which disappears on the next start.  Any ideas where my issue is?

[dna9656]

Any weird electrical problem is  usually a bad ground or several bad grounds. GM has all the ground locations in their manuals, probably the electrical manual, you won't find it in the regular maintenance manual. You might do a search on the Internet for ground locations on your truck. These trucks are known for loose and /or corroded grounds. You could have a bad ignition switch. Possible neutral safety switch; other guys will chime in, I'd see what else the forum has to say.