AnswerMost GM cars anbd trucks locate the starter relay right on the startrer itself. GM calls it a solenoid.
Actually, there is a separate relay as well as the solenoid. This relay is in a fuse panel, either under the hood, or maybe even in the kick panel fuse panel.
If you can get to the starter, try this:
Turn the key to "on". With the car in PARK (double check this, it's important)
look into the starter area. You'll see a big cable and a small cable both coming to the starter. Use a screwdriver to short these two together, keeping your hands, arms and hair AWAY from the belts!
If the car turns over, starts acts like it's going to run, but quits as soon as you remove the screwdriver, you may have a bad relay. This relay not only allows the starting system to START the car, it also allows the ignition system to function.
That's why it starts and tries to run, the power is back feeding through the system and giving power to the ignition coil when you short the starter. As soon as you pull the screwdriver away, the ignition loses power, and the engine coasts to a stop.
I've seen the relays priced anywhere from 25 to 50 bucks, depending on where you get it.