READ YOUR CODES!!!! That's why the MIL (Check engine light) exists. All you need is a paper clip.
Here's a picture I hijacked from Corral.net:
You don't need the voltmeter. Just jumper the gray connector depicted as that little rectangle jumpered to the connector in the upper right bevel corner. The double-headed arrow is the paper clip. I just keep a wire with a spade connector on each end in my glove box to do this on the road.