Thread: Onstar hack 2001 Yukon XL

Originally Posted by grepzen

No, same network for mil and pub use. The mil has access to more signals that provide greater accuracy.

LAT/LONG + HEIGHT!!! Sweet for using as aimpoints for PGM's.

Nice information guys. Thanks for the links, I will be sure to look further into this

Originally Posted by WakeBdr

Just make sure you have the correct Onstar hardware. I have a 2003 Tahoe that has a different board in it. The 2003+ models have different hardware and cannot be hacked using this mod.

OnStar started its switchover in 2002 so some cars have the correct modules and some don't. The easiest way to tell is if there are two boxes - one is the computer, the other is the cellphone used by OnStar. The newer modules are a single box with the GPS and cellphone integrated into the circuit board.

Originally Posted by Peoples

How would you go about figuring out that you just need to solder these 4 pins to your serial port?....thats crazy? Do these guys work for onstar?

No, some people just enjoy hacking stuff apart to figure out how it works. Reverse engineering can be fun sometimes.

The GPS module used inside the older OnStar boxes is actually a Motorola GT Plus OnCore GPS receiver. Details are here - http://www.motorola.com/ies/GPS/products_legacy.html. I pulled the OnCore module out of an old OnStar unit I got from the junkyard and used a modified version of the first circuit on this site - http://neutrino.phys.washington.edu/~berns/K2K/TACGPS/ - to build an RS232 serial interface for the board. Its been working great ever since. I can post the modified schematic if anyone is interested.

I have a 2001 Tahoe, which I assume has the same setup as the Yukon. My GPS antenna is located right behind the rear view mirror, in the top center of the windshield.

The Onstar GPS antenna seemed to get a pretty strong signal. But I don't use it anymore, so I can't tell you how strong of a signal I received, compared with the signal from an antenna mounted on the roof. I can't recall ever having a problem determining my location or receiving a satisfactory signal strength, though...

Originally Posted by Peoples

How would you go about figuring out that you just need to solder these 4 pins to your serial port?....thats crazy? Do these guys work for onstar?

It's not that complicated... Inside the Onstar box, plugged into a socket on the Onstar board, is a Motorola Oncore GPS module. This GPS module is used in other equipment, not just in Onstar stuff, and the pinouts are all labeled in the freely available Oncore manual.

I bought the same Motorola Oncore unit off of ebay that is used in the Tahoe. It came with a serial interface board and an antenna, so I just used that one and hooked the original car antenna back up the onstar unit, so now my onstar light is green again... And I mounted the antenna on the roof, in front of the sunroof. The cable runs behind the sunroof rubber edge? (I don't know what to call it), then over the roofliner, then down the a-pillar, back behind the dashboard, etc...Looks good, though...

i have a 99 escalade that has onstar...i already bought the bu 303 and its working great..would i have to spend some money to get the hack to work? if so ill just stay as is..if not ill do it and sell my bu303