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Discussion Starter #1
At the beginning of July we noticed that the Navigation system didn't show the correct mapping information. The top right of the screen shows a GPS with a line through it. We don't use the Nav very often, so not sure when this issue really started. The dealer had it for routine maintenance (oil, rotation, etc) the last week of June. I noticed the next day after we picked it up that the maps were not working and "thought" maybe it just needed to be driven around a bit more since it had been sitting in the garage all weekend. We drove from KC to STL a few days later and it still didn't work.

- Maps show me in Detroit
- GPS with a line through it on top right
- OnStar LED is still Green
- Nav Info showing 0 satellites

Any ideas on what to look at here? Where is the antenna? Where is the splitter I have read about?
 

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How bad does your neighborhood look? Maybe you really *are* in Detroit!

Sorry. Couldn’t resist that one.

I don’t have NAV, and I’ve got a 2011(so maybe somewhat different) - and I’m cramped for time here (gotta get to work), but my Helm Manual says the NAV antenna is the one on the roof. There are actually 2 more antennas in the rear window glass for AM/FM, and the schematic shows 2 coax cables from a “K46” Radio Antenna Module going into the radio unit.

The only thing showing up for “Navigation” in the Index (and these Helm manuals are famous for deficient Indexes ... I’ve added numerous entries of my own along the way), is for a “Navigation Signal Splitter”, which is a small box, sitting vertically, held in with 2 bolts, under the driver’s side knee bolster, above the brake pedal. The manual says “Disconnect the electrical connections”, so it has a couple of wires plugged into it.

The knee bolster is just the flimsy plastic panel held in with either 4 fasteners (Nox), or 2 fasteners (Terrain).

But personally, I think your system is working, it’s just confused as to where it is. I think you’ve got either a configuration problem (lost its “home” position), or your software got updated or needs another update (now) ... for whatever reason.

Good Luck! I gotta run ... really late now!!

UPDATE:
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There are also DTCs (OBD Codes) like "B125C" which would indicate a indicate a Satellite Antenna 1 Circuit Short to Battery, or Ground, or even an Open Circuit.

Wait ... THIS might be what it is: The "Communication Interface Module". A dealer scan tool (sorry, I know) is capable of reading the status of this module. Things like "GPS signal present YES/NO", Signal Strength (a number between 0..100, but "68" is expected, for some reason).

This module is located very close to the Splitter behind the Knee Bolster. It's a rectangular box with two bolts on one short end, and one on the other short end.

As for the routing of the antenna cable, it's depicted as coming off the antenna, going toward the liftgate, then looping back, along the roofline, on the passenger side, where it turns left, and goes through a hole above either the driver's seat or pillar between doors, then down to the dash and into the Communications Module, Splittler, and Radio.
 
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I have had similar problems. I believe that it was water getting in, but I let the dealer sort it out. The GPS antenna is the little numb under your radio antenna. I know my dealer unscrews the radio antenna to take it through their car wash.

I had the wrong city and the GPS with a slash a few times, but more often my issue was that my location was off by about 10-100 yards. Meaning, the GPS was going the right direction, but constantly thinking I was on side streets and telling me to turn. Out on the interstate, it just didn't know what to do. Now when I take 16 hr trips, I take my old garmin as a back up measure. I never felt it was fully resolved since there was no clear cut problem and solution, but the issue has been gone for year. Maybe try unscrewing your antenna, look to signs of water, and leave it off and park in the sun. Let it thoroughly dry out. Odds are good you have some more significant wrong. I do kind of recall seeing someone else with this issue here. I think they found a TSB that there was a software glitch. You dealer should be able to check for TSBs for free.

If you google it, there was a calibration procedure for the internal compass. I think you need an empty parking lot, and drive in circles. Probably not related though, the GPS should trump the compass.
 

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Discussion Starter #5
Today I popped the hood to add washer fluid and I see blue crap hiding under the cover for the Negative battery terminal. Crap....
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Nasty looking mess hiding under there.
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A bunch of baking soda and water cleaned all of that gunk off of there easily. The biggest problem was that the vertical battery clamp was corroded badly and didn't want to release. I had to work for about 15 minutes to get the clamp off of the battery post.
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The cause of all of this? The case split.
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The Terrain is my wife's vehicle...but she usually drives my vehicle since it is the high mileage beater....about 4 years ago my vehicle left her stranded at work....because of....a cracked battery case around the terminal. On that car, it was bad enough the cable clamp actually broke. In 20 previous years of car ownership, I have never had battery failures like this. On my car, it is all completely hidden unless you pull the engine bay covers off. At least with the Terrain I happened to see it when filling the washer fluid....otherwise I bet within a few weeks this clamp would have been destroyed and broken off as well.

Why in the world is this added to this GPS thread you may ask? Because after the battery was disconnected, our GPS is functional again. Go figure. It has only been a single drive to test, but for the first time in over a year, our car didn't think it was in Detroit. I will keep an eye on it to see if it continues to behave....and when it doesn't, I'll disconnect the battery again to reset what ever it is that doesn't cycle when the ignition is off.
 

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Do yourself a large favor and get a new negative battery cable.
The neg cable splits 4 ways, the engine, unibody frame rail, current sensor, and dedicated ground to the BCM.
A corroded cable can cause all kinds of problems.

Get a new OEM cable, not a cheap one and you will get a new current sensor installed on it.
 
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Discussion Starter #7
It will be on my list this fall. I need to see how much work it will really be to determine if I will tackle it myself or not.

My TL ate through that clamp and cable....it was a $65 part and the dealer charged about $100 for install. I need to compare what my local GMC dealer will charge for a similar service. If similar to Acura, I will drop it off for them to deal.
 

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I did my negative cable about a year ago when my original battery died.
Pull the battery and battery tray and everything is right there, get it from the top.

Took me about an hour and a half, I was cleaning a few things as I went.
I could do it in an hour if I was on the flat rate clock.
This was for a V-6.
 
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