A dealership tech can't fix a problem he can't identify, so your job is to identify where the problem is and conditions under which it occurs. At $125 per hour or more, it gets pretty expensive, quickly, to have the tech look further.
I would suggest you subscribe to ALLDATDIY.COM (or similar online publication). I believe it costs about $25 for a 1 year subscription and about 2X that for 5 years. Either choice will likely save you many times the cost of the subscription. When you subscribe, you get information about YOUR TRUCK, not other similar trucks, other years, 4X4 vs 4X2, etc. So the coverage is not as broad as other hard bound reference books, Chiltons, etc.
ALLDATDIY.COM has all the DTC's for your trucks and all the TSB's which can be very helpful to see if there are similar situations which have been addressed by Chevrolet. Example in my 2008 version, there are 10 TSB's for Electrical problems.
Here is the outline for one of them:
Electrical - Multiple Warning Lamps/Shifting/Driveability Issue Information
Electrical - Multiple Warning Lamps/Shifting/Driveability Issue
Information For the Procedures to Diagnose and Repair the Above Conditions
Chafed Wiring Harness at Transmission Case Retaining Clip
Multiple Wires Cut and/or Corroded
Inspection of Fuse Block - I/P (Left Side) For Loose Connector X1
Chafed IP Wiring Harness Near Park Brake Pedal Assembly
Chafed IP Wiring Harness at Left Side Junction Block Mounting Bracket
Chafed Wiring Harness at Adjustable Pedals Motor
Chafed Wiring Harness at Transmission
Chafed ECM Wiring Harness From Bracket Contact Near Engine Intake Manifold
Chafed Wiring Harness at Rear of Engine Intake Manifold
Chafed Wiring Harness at Chassis Body Mounts Left Side Frame Rail
GMLAN Terminator Resistor 2007 Vehicles
Data Link Resistor 1 2009 Vehicles
Rear Chassis Mounted Data Link Resistor 1 Chafed Wiring Harness
Inspection of Engine Harness Connector X109
Inspection of Engine Harness Connector X115
Hybrid Models (HP2) Chafed Wiring Harness
Hybrid Models (RPO HP2) Data Link Resistor 2
Hybrid Models (HP2) Equipped With Onstar(R)
Lost Communication With Various Control Modules and DTCS Set
Inspection of Electronic Suspension Control (ESC) Module Connector
Repairing Fretting Corrosion
I believe you have a circuit problem somewhere, perhaps a problem on the LAN communications line, fuse box, etc and it will take lots of detective work to shake, twist, pull, squeeze, etc, those wiring bundles until you can find the one where the problem exists, and you can reproduce the problem in your garage. Once you can find a way to reproduce the problem, a tech can figure out how to do the repair if you are stumped about that part of it. The answer/solution/fix for one person is unlikely to be the same as found on other trucks although possible. It might be good to start a post where all of you with this similar problem can post what you have done and what you have found so that all can benefit by the collective effort and knowledge.
I would make sure that the batteries are fully charged; that the battery cables inside and out and both ends are absolutely clean and shiney and tightened properly. Don't just look at them, get out a metal brush or sandpaper and make sure to remove any corrosion whatsoever. Check both ends of the battery cables, and don't forget the alternator cable. Add a light coating of di-electric grease before putting back together. Check your ground cables in a similar manner. If you live in salt country, this is especially important. Maybe even run and additional ground from the firewall ground point near the brake booster to the engine or battery, just in case the ground isn't 100%. Check and clean your mega fuse connections on the passenger side firewall in a similar manner. Make sure to disconnect both batteries when starting. Gotta have the basics correct before anything else electrical can be expected to work correctly.
2008 Silverado LT, CCLB, Edge Insight CTS
2009 Arctic Fox 29-5T, Silver Fox Edition, Onan 3600 LPG generator