Tomato

Had them years ago on my 2008 Silverado - loved them.

Had the same thing and it was caused by a bad Michelin tire.

I sent an email to Banks asking if they have observed this. In addition, I asked if they had a programming solution of any kind.

Haven't had that issue, but could it simply be a loose ground or primary positive battery cable? I've experienced similar issues as a result.

America's Tire ordered larger stems and will attempt to rebuild the trailer sensors for me. I will report back when complete.

Anyone found a bull bar for our 2020 HD's yet? Built in light bar a big plus...Thanks.

Key takeaway is that it sure seems to be coming from the EGR system.

Did some searching and Banks did a teardown on the L5P. Looks like it could be the new EGR system. They mention valves, so it could definitely be that. See pic and link. http://www.trucktrend.com/how-to/engine/1702-a-peek-inside-the-duramax-l5p

This is the second area where the sound is most pronounced. It is the back tube coming off the top of the motor.

I spent a few minutes with my listening device (stethoscope) and found that the thumping was most pronounced and resonated where I am pointing with the orange handle in the 2 pictures. I do not know diesels well at all, but I believe this is all part of the turbo, right? Good to note that I did not pick anything up at the bottom of the motor or on the tops of the valve covers. Thoughts?

You don't think it is at too slow of an RPM to be a rod knock? Too bad we can't connect a timing light to compare. Or is there a way to connect some sort of tool to each cylinder that tells you when it reaches TDC?

For what it's worth, and as I mentioned in another post, it definitely sounds like a pump of some sort to me. I notice that the knock comes on for 1-2 seconds right at cold start-up, then the overall sound of the motor changes (hard to describe, but like a higher idle and maybe a change to injection timing versus compression due to the cold start). Then the knock stops for 2 minutes or so. Also, it seems to be knocking at less than engine speed (could rule out an issue with rotating assembly). If it is not the fuel/lift pump, could it be something with the turbo? I am not familiar with how it works. Could it be some sort of waste gate "puffing" or something?

There are 2 TSB's on this. The first calls for Road Force Balancing of the tires, and the second is for a power steering module reprogram. Mine was fixed with replacement of 1 front tire. There are lots of posts on this.

One of the key upgrades to get the new towing capacities was to the overall cooling system. These definitely seem to be running a lot cooler than my previous Duramax, and neither of my last 2 came with a winter grill cover to help it run warmer in cold temps...

I had the Roll-n-Lock way back on my 2008 Silverado Long Bed. I really liked the locking mechanism and that it retracted like a window shade. The Retrax fit and finish is much nicer, but the locking mech is not as nice, and it needs to be pushed to open. And they do fit in the garage. Chevyguy85 just has the wrong garage :).