I have a 2003 Yukon SLT and over the past few (very cold) days there has been a rhythmic noise coming from the passengers side cargo area. It occurs every 2 seconds and repeats over and over. SOund like a whoosh of air and a squeek (cant make this stuff up). I have everything turned off and it still happens (no heat on, stereo, etc). Anyone know what component is tucked away back there that might be causing this?