Sorry for the delay getting back to you; as usual, I’m just managing to keep my nose above the water line. I’m not quite sure what the issue with your Nav might be. There are 2 separate systems involved. The first is the compass. In the original installation, the compass sensor is part of the rear-view mirror. The calibration described in the forum is for this system only. The Nav system can’t give you the direction you’re pointed unless you are moving because it has to calculate the difference between 2 or more GPS fixes. I checked for TSBs and found nothing applicable. The antenna for the system is the same one as for satellite radio. There is a splitter module inline between the cable coming from the GPS/Satellite antenna that plugs into 2 separate connectors on the back of the Nav head unit (a pink one and a yellow one). See the attached diagram. I have had issues with all 3 components (antenna, cable and splitter module) on different vehicles that cause issues like you’re describing. The problem is that the only way to diagnose this issue is swapping parts. I have some antennas and cables that I have used for testing (didn’t fix the problem on particular vehicles), but I think they are all truck parts and the connector genders may be wrong. I could try re-flashing the Nav unit, but it’s not likely that the software is at issue after 2 years of normal operation.