Rapid Horn Honk - Reminder of Something?

[Back in Black AT4]

Hi there - 2020 AT4 6.2L Sierra owner here - every once in a while upon turning off my truck, I'll get a rapid horn honk burst similar to when you leave you keys in the truck...it's almost like it is trying to notify me of something...I had some DTC's stored in memory...I wonder if that is the cause and I should get them cleared by the dealer (or get a tool to do it myself)?

 

Any other ideas?

[Colossus]

did you try honking back at it?