Ok, I have a 2016 Yukon XL Denali, and after having the signal disappear a couple times in 2017, now I have the red light on my ONSTAR mirror and my GPS says I am 50 miles away and can not locate me. I called GM and asked about the recall 15155 and they said my vin number was not part of that recall. The only thing I could do is have my case escalated for the time being and I now have a 48hr wait to see if a supervisor can investigate the matter. I told the representative that I was experiencing similar issues as mentioned in the service bulletin, except I haven't seen any water inside the car. She said then it is not the same issue then.
So after I got off the phone I went outside and inspected the antenna. I thought well maybe it doesn't have a tight seal to the roof? As soon as I started inspecting the rubber seal and nudged it with my fingers a decent amount of water came out. There is a weep hole in the rubber but it is on the back (high side). The water appeared to be pooling in the front. (the lowest point).
We have a 2000 Tahoe with approx 250K miles on it, and the thing runs like a champ. The LS motor is what sold me. I purposely purchased this car a year after it was released so they would have worked out all the bugs. Between the the roof bow/noise issue, and some other things, I think they figured it out by the time we purchased ours. I have been really happy with this vehicle so far. The 6.2L LS and 8 speed transmission, with the MRC has been as good as expected. Even getting on average about 17-18 MPG around town, and 22 MPG on the freeway. I hope GM will take care of this issue with the antenna, so we can continue on with it for many years to come.