Not sure if this helps but my past and very recent experience is: I owned an 2002,2006,2010, and now 2013 Avalanche.
Last week I purchased Prodigy P2 at CW and it had to be hard wired per the Prodigy rep, no harness but wires were blunt cut with tow pkg. my previous Avalanches were the same but GM had provided the harness, they no longer do that.
If you look to the left of steering column you (up pretty high) should see bundled and wrapped and possibly marked for the BC. My thinking is unless you want to remove to another vehicle, just use the one harness that is included with the P2 and just joking the wires with the proper connectors to the blunt cut ones provided by GM. Don't confuse the harness connection with the other harness connectors, they are merely plug ins for dealer and mechanic to test systems etc etc