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Saab9-5 · 03-12-2005, 06:16 PM

Quote: 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.

Quote: 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.

03-12-2005, 06:16 PM	#14
Saab9-5 Constant Bitrate Join Date: Mar 2005 Location: Ponta Delgada, Azores Posts: 222	Quote: 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. Quote: 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.