maybe try wiggling the harness along it's length, w the engine running and while watching it log if you can? For my '12, I believe the harness goes across to the engine, then down under the front of the engine, then back to the ckp sensor.
I can't believe a dealer person would BS me. I never got anything about the cover warranty with the purchase. I just looked in the truck and nothing there, unless they will handle it for the customer.
Amp Power Steps are worth every penny (or should I have said dollar?). They go down and out further than any other step bar and are useful to enter AND exit the vehicle. With bars, people use them to step in but just drag their leg across the dirty bar when exiting as they aren't useful being so far inward. Power steps also go up and tuck away preventing them from hanging up on anything. I've had mine for 14 years and they've been completely trouble-free with just an occasional spray of lubricant.
Similar to what AndrewF said, on my 2024 2500HD, I used 84663240 harness, 84670050 harness, 84166962 retainer, and 25774623 receptacle. Everything simply plugged together, no individual wiring. All from GMPartsStore.com for about $152, including shipping.