Yukon 6.0L P0300 and other codes

[Model.700]

Hello GM guys, I'm working on my fathers 2003 Yukon Denali with a 6.0L engine. As of today, the truck has been shaking on idle, and vibrating at speed. I went to the local O'reilly's and got the codes of

 

U1000 Class 2 Data Link Malfunction

U1016 Lost Communication With Engine Control System

U1096 Lost Communication With Driver Information & Instrument Panel Cluster System

P0300 Random - Multiple Misfire Detected

P0305 Cylinder 5 Misfire Detected

 

I pulled off the top and right side plastics to get ready for what's to come. Where should I start, fuel, spark, or air? Should I replace coil packs or start on something cheaper? The coil wires appear to run through the header and under the engine, which is weird.

 

Any help is good help, thanks!

 

 

EDIT: thought I might add the truck can run and drive, it just shakes from stop to medium speed

[Dnt]

Pull #5 spark plug and take a close up pic and post it. If it looks like this one we will have solved your issue.........

[Model.700]

Pull #5 spark plug and take a close up pic and post it. If it looks like this one we will have solved your issue.........

I'm not familiar with the whole coil pack design, is there a plug under the pack, or no plug at all? Thanks for responding!

[rdnkcpa]

Coil packs are on top of the valve covers. A spark plug wire runs from the coil to the spark plug. I think you are used to looking at Overhead Cam engines which usually have the coil pack on top of the plug. The plugs are on the side of the head between the exhaust manifold outlets.