2007 Freightliner Columbia Detroit Shut Down Issue

Can anyone help figure out what's causing truck to start fine shut down while idling then wont restart? The dash won't light up. When it does start as long as I give it throttle it won't shut down. When I take my foot off throttle it dies and dash dies. Two mechanics later including Freightliner dealer still no answers. Put 4 new batteries in changed ignition fuse, power relay in dash fuse box. Checked wire connections are right to and from batteries. Before truck shuts down I can get power relay click a couple times then dash dies truck dies.