Need ATF exchange information for 2015 Tahoe

[bdbull]

I'm about to do an ATF exchange, pan drop, filter change, etc. on my 2015 Tahoe. I've done this before on this vehicle (4 years ago) and my 2010 Avalanche, but didn't take any notes or pictures along the way. Now I can't remember which line I pulled to do the exchange. I have the brass adapter that "plugs" into the radiator in order to pump the fluid out but I can't remember where I need to put it. Can anyone help me determine where I need to put this adapter in order to pump the fluid out? Here are some pics of both sides of the radiator and the adapter. I've labelled the pics D for driver, P for passenger and the lines are numbered in order from top to bottom. If I figure this out, I promise I'll take pictures and notes this time.

 

[swathdiver]

I'm not familiar with the K2 cooling system. In general, you want to insert that adapter at the line coming out of the internal transmission cooler which on your 2010 was the top line on the passenger side near the air filter.

 

[bdbull]

Wanted to follow up on this in case anyone comes looking for this info. Everything I found online and ChatGPT said the return line was #2 on the passenger side. I can confirm with 100% certainty that is not the case on my Tahoe, and it was not fun to clean up. It turned out to be #2 on the driver side at the bottom of the radiator. Procedure went flawlessly after I got the mess from the first attempt cleaned up.