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What You Will Need

Your vehicle came with OnStar. You had purchased it new and included was a free year of service. This was nice. Neat little features. But after using it for a while, you found you really didn't have much use for it, let alone, paying $19.95 a month for it. Not to mention, the analog OnStar systems have been all but left unsupported. Now your vehicle has about $1000.00 worth of hardware in it that is useless. Until now!

Why not tap into this hardware and put it to use? You paid for it, you own it. Sure, you can buy a Portable GPS, or even a "Puck" to stick on your roof for a similiar effect, but what fun would THAT be?

The following pages explain how to do this, step by step, on a 2002 Chevrolet Avalanche. Most OnStar systems use the Motorola Oncore GT+ Receiver. You will need to verify that if you have another vehicle other than the Avalanche. Even if you have an '02 Avalanche, I still recommend checking. Have heard some have the Sony unit, and I have not yet come up with the pin-out assignments for this unit. This will be described later.

To utilize this modification you will need:

  1. A laptop with a serial port. I have tested this using a port replicator to USB setup and it works fine. May be an issue with the computer thinking the Com to USB adapter is a mouse on boot-up. For now, boot up before connecting the OnStar cable to the port replicator.
  2. WinOncore Software. You can't download this anymore. This link is no longer available. Contact me to get a copy.
  3. RLC-1 3v/5v RS232 Level Converter available here (International) or Here (US).
  4. Female DB9 to Male DB9 Serial Extension Cable. (Radio Shack)
  5. Tools - Torx driver set, Soldering Iron, and misc. screwdrivers and wrenches.
  6. Mapping software of choice. You will need a generic NMEA compatible program. I am using Microsoft Streets & Trips 2003 with great results.
  7. Patience and a steady hand. It can take some work to remove the box let alone find it. The soldering can be tedious.
  8. Streets & Trips Refresh Rate timing patch.

So, let's get started. Remember, this is based on a 2002 Chevy Avalanche. Different model vehicles hide their OnStar units in different places, so good luck.

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