First off, this site is awesome! There is so much good info here for AVIC users. Hopefully you guys and lend a hand with my situation.

I have an 02 GMC Yukon XL with an N1 in it. The unit was installed by Al & Ed's locally, and I have used it for the past year without problems. Everything on it is original with no mods or hacks other than the parking brake being grounded (per my request to watch DVD's while I am moving)

About 2 weeks ago, I realized that my superchips programmer that I used to use on my dually works on my Yukon as well. I thought would try to get some better gas mileage out of it, so I tried to modify the stock ECU. My Yukon has Onstar, even though I don't use it. When I installed the superchips, it said to remove the fuse to the Onstar to continue. I did, modified my ECU, and drove home from work. On the way home with the Onstar unplugged, the navigation was all out of whack. The speed was way faster than I was going, and the map showed me almost 100 miles away from where I was by the time I got home 11 miles from work. When I got home, I reverted the superchips back to my original stock ECU settings, and reinstalled the Onstar fuse. Onstar light came back on, and truck was back to stock. I reset the calibration on the N1 and drove to and from work over the next couple days. It won't recalibrate. I don't get any signals now from the truck to the unit, and when I also checked to see if I had sat signal, it says OK, but doesn't show satellites like it used to. I used to be almost full sat reception, now I have none, but it says OK.

I checked all my connections to the brain and the unit. Everything seems to be as it should. I tried to reset the unit, unplugged the battery...basically everything I can think of. I would rather fix this myself without having to go back to the installer and pay someone for my mistakes. Anyone have any ideas to this??

Thanks in advance!

Dave

Are you saying that you left the OnStar fuse out after you used the programmer? You are supposed to reinstall the fuse(s) afterwards. You only need to remove the Info, SEOB1, radio, etc. fuses during the ECU reading and programming, then you reinstall the fuses.

No, I re-installed the SEOB1 fuse that powers the Onstar after I returned the ECU back to stock. The Onstar light is green now and appears back in normal operation.

Did you reinstall the fuse after uploading the Superchips program?

No, you can't have that fuse in while installing the program beacuse the onstar is on. The superchips doesn't work, read or program with the onstar working.

Fuse came out to program, was out while using program, and went in after I returned the ecu back to stock.

For some reason, I didn't catch when you said to reinstall after programming. I just reprogrammed the ECU with the superchips again, and reinstalled the fuses. I reset the N1 from the front of the case and put it back into sensor initializing mode. I still don't have any sat signal, but it says OK next to the little satellite symbols. We'll see what happens now.

After over 100 miles and 2 days now, still no satellites show up, and no position movement. Any other ideas?

Bad or loose gps antenna.

First of all, you should replace the fuses you removed while programming the ECU ONLY after you are done with the Superchips upload. You only need to remove the fuse while saving the original (stock) program and uploading a program into the vehicle, because the OnStar unit peiodically sends out data on the same line as the OBDII port, so the programmer will save this data as part of the stock tuning file. Very bad. Tow truck time. It's also not a good idea to have a cellphone nearby while saving or programming, since the phone puts out so much radiated noise (the bpppt, bpprrt, bzzzrrrt noise you hear through your stereo when your phone rings or is in use) that the programmer will save that digital noise as part of the program. Again you are pushing your truck, walking and cussing. Now, as far as your GPS, cntrylvr is probably right. It sounds like your antenna is bad or not connected properly. Where did you put it?

I reinstalled the fuses, returned the ECU to stock. The Yukon runs fine, so I think I lucked out. Thanks for that info! I would have been pissed if I had screwed up my ECU! I redid the Superchips programmer the way you described, and it is working fine, so I am ok there.

As for my antenna, I don't know what could have happened unless it just went bad. It was weird that it just happened to happen when I did the programmer. When the program was first installed, and I didn't replace the fuses like i was supposed to, it still worked, it was just reading way faster than it should, which I just related to me modifying the size of the tires in the programmer. Then when I returned it to stock, the GPS stopped working all together.

The location of it is right above the drivers head on the roof, and I have always had all but 1 of the satellites on the signal strength. I checked the connection at the remote unit, and it seems ok. I checked the length of the cable to the antenna, and there are no pinched areas, rubbed areas or anything that would lend to it being bad. I guess I will check the shop that I had it installed back in April last year and see if they have another antenna.

Something that I also noticed is that the speed sensor isn't reading anything anymore. Could that be related to the GPS antenna not working or could that be another problem with the VSS signal now not working as well?

I should have left well enough alone!

Here is something else you should know. http://www.pac-audio.com/bulletins/bull ... h=C2R-GM24