2015 GMC Sierra Misfire w/traction light on

[Gurprit Dhaliwal]

Hello team, new to the forum and new to the GM truck world. 
 

Issue: truck seems to be misfiring under heavy load. The engine light will begin to flash and traction light comes on. After a minute or so, traction light will go off but engine light will remain. Codes cleared and drives fine until another misfire. No issues while truck starts. 
 

I’ve replaced the coils, wires and spark plugs. Cleaned up 4 grounds (ECM, and the 3 under the truck on the driver side). 
 

I’ve attached the codes present. P300 and rest all U codes. I’m at loss. If there is anyone experienced this please help! Next step is the stealership. 
 

link to video. 

Edited March 20 by Gurprit Dhaliwal
Added video

[silveradosid]

even though your in the wrong forum, misfires under heavy loads is an indication of your cats are plugged, constant U codes can be caused by a weak battery