2001 GMC Jimmy

Recently having major problems starting my 01 jimmy. Sometimes it will start with no problems, usually it won't start no crank, no nothing. As if there was no charge in battery.(Brand new battery at full charge) brought the truck to gm shop, checked thoroughly said everything is running fine, starters fine, charging system fine etc. Even got the to disengage remote start, still no change. Funny thing is when at gm, hooked up to their huge charger, started fine everytime? Been asking other mechanics, usually told me starter? Or crank sensor? One even told me to run a secondary battery? Which I don't want to do if not necessary.(Haven't tried any yet) So after multiple towing and shop charges, still scratching my head. Please help, any information will be greatly appreciated.
April 21, 2007.

Could be the build-in security guard system-theft deterrent device that's preventing it from starting.

Or it could be losing power from the ignition switch thru the neutral safety switch, starter relay or the starter itself.

What's the problem here, Is it the starter cranks the engine over and refuses to start or won't even crank over at all?

Apr 22, 2007.
Won't crank at all

Apr 24, 2007.
I had a similar problem with my 97 sumurban randomly loosing power and not starting and it was the negative battery cable connection at the battery. When I had a new battery installed the person didn't get it tight. Fought it for months till I figured it out.

Duane Olson
Jul 11, 2007.