Bsull

Hi and I hope someone can help me. I have a 2010 GS coupe with the Bose sound system and XM. I do not have factory nav. I have two Garmin GPS units, an older Streetpilot 2730 and a brand new Nuvi 1450.

The problem is I lose all GPS sat reception when I change from FM to XM. I've tried putting the GPS unit on the left side of the dash, the center, the right, same problem. I've tried holding the unit in the center above the rearview mirror, same problem. I tried putting the unit down on the center console, same problem. The only place both units will work is about a 1/2 inch in front of the dash above the center a/c vents and behind the seats. Not really a solution. The problem is very repeatable, with both units. Sat reception comes back in just a couple of seconds if I change back to FM. Garmin is no help. They suggested I have the Chevy dealer move the XM antenna.

Has anyone else experienced this problem? Does anyone have a potential solution? Any help or suggestions would be greatly appreciated.

vetteright

I have an '08 coupe with XM and I have a Garmin Model 785 WT mounted in a cup holder bracket (installed in the forward cup holder) which elevates the unit to a height of 5" above the top of the center console to the bottom of the unit (8" to the top). It is approximately 7" from the face of the radio to the front the nav unit. I listen to XM all of the time and I have not experienced any loss of signal to my nav. The XM antenna(s) on my car are located in the outside rearview mirror housings (I think that yours are, too, but not sure). Mystefying for sure; obviously something must be interfering with your Garmin, but can't imagine what it would have to do with the XM signal.

Bsull

Thanks. My problem is very repeatable. Select XM the sat reception goes away over about 5-8 seconds. I can see signal strength decrease on the GPS info page. When I select FM sat reception returns but in much shorter time period. Since nobody else seems to have this problem, only thing I can figure is bad/open ground somewhere in the car between radio control, antenna or reciever. Car going in for service soon, I'm gonna ask the dealer to take a look. I'll let you know how it turns out. I'm also thinking of trying an external GPS antenna, but that limits the units that I can use/buy, the Nuvi 1450 doesn't have external antenna capability. I would rather solve the problem and not have to use external antenna.

Bsull

Here's an update to the issude I posted a bit ago. Brought the car in to dealer to see if they could find problem. Unfortunately, even after explaining how, what, where, when and leaving the car and problem GPS with them, their answer was "could not duplicate the problem." I didn't drive more than a 1/4 mile away and I lost GPS signal so I don't know how much troubleshooting they actually did.
I did a little more myself, here's what I found.

With an external antenna connected to GPS, I cannot get good reception if I put the antenna anywhere forward of the steering wheel. Placing it on the dash, reception drops in about 5 seconds to no signal. I don't know how this figures in to the XM interference, but if I move the antenna toward the Onstar antenna in upper right of windshield, I can watch reception decrease to zero in 1 or 2 seconds. I I put the antenna behind the seats, pretty much anywhere, reception is acceptable, with windshield mount and antenna on the bottom of the rear glass, I get best reception. Makes GPS useable but still not the best solution.

I think my coupe has electronic gremlin somewhere and it's gonna take some time to find it. I'll update as I get more info. Stay tuned.

Bob