Take it to a dealer.

 

I absolutely 2nd @low-tec
Take it to a dealer

 

I hard were you accelerating? just wondering

 

I did take it to a dealer, mis-diagnosed on throttle body. I already have an appointment on Monday at my purchasing dealer. There seems to be a fair amount of searchable events similar to mine and was hoping for some insight on what the fix might be. There's been reports of faulty harnesses, fuel injectors, modules, etc. The method of acceleration was your basic more gas pedal going up hill not gunning it. During the limp home it would retrigger with even the slightest push of the pedal....I had to feather the gain in speed over 5 or 10 seconds. Imagine that on I-95 😝. Once it happens it's a pull over, turn off vehicle, open door to shut the electronics down and restart. This has to happen 4 times in succession before the CEL goes away.....this should be fun.

 

Okay, what code is setting?

 

The generic P2101 Throttle Actuator A Control Motor Circuit....

 

That's a missing piece of relevant information.
Since the the throttle body has already been replaced, this is most likely a wiring issue.
Your going to want to start with carefully checking the wire harness from the throttle body back to the ECM, carefully for points where it has chaffed against something, or been pinched during assembly. Then unplug both connectors and test the terminals for proper tension. If that's good, test each circuit for good continuity using a digital ohm meter, you want to see a couple tenths of an ohm at most, then check that they all have infinite resistance to a solid ground. Remember, we have both ends of the circuit disconnected at this point. If you still haven't found anything at this point, I would say you need to test each circuit's ability to carry some load. Connect one end of the circuit to a verified good ground, then with an incandescent test light (not an LED) connected to battery positive power touch the other end of circuit, the light should have it's full brightness. If the light is dim, or doesn't light at all, you have a compromised circuit.
From here you have 2 choices, you start disassembly the harness to find point of failure, I have had some luck in this and been able to find points where the insulation is suddenly narrower, this is because there is brake in the conductor inside. But, often times the more expedient repair is going to be to restring this circuit.

Hope that helps. Good luck in getting it fixed.

 

Dropped her off at the dealer yesterday and got a loaner 👍🏻 They managed to get her to jump the shark twice yesterday and called late afternoon saying it would need to stay another day. Don't know if that's good or bad. The phone app lists the service issues as Engine & Transmission System and the system status lists the Tranny and the Throttle Control....guess we'll see later today.

 

I got the truck back on Thursday and drove it some miles and all seems well. They verified the P2101 code and over the course of the 4 days were able to recreate the kick-out to limp mode on acceleration I was experiencing. Got numerous Onstar notifications to this effect. They did trouble shooting on the throttle body per Document ID 5417364. Replaced throttle body per service document ID 6143238. Test drove and no further issues noting that issue could be triggered when vehicle is hot and throttle open past 35%.They did additional testing on wired connections. Found that the ECM was loosing connection on K20, pin 30. All other connections tested good. Replaced the ECM and tested on interstate with elevation change and an additional 25 miles in mixed driving with no issues. (*almost). Friday morning I went out to reset some settings reset by the service techs and looked under the hood.... 😝 The techs forgot to reinstall the cowl/shroud over the engine behind the intake. Drives fine though and I'll take it back on Monday to get the covers reinstalled....

 

Glad to hear that they got it all sorted out
Oops on the Engine Cover
After working on something for so long they wanted to see it gone and just lost track of the cover