Polarity on a 1994 Plymouth Voyager

Hello all, my little brother has a problem with his van 93 Voyager 3.3. I removed his negative cable to check for a draw and I happened to also hook up the test light to the negative post and then to the negative battery to ground terminal the test light lit up! I don't think this is normal for even a Mopar product. By the way one of his complaints was a spark when he tried to connect the negative terminal to the battery. Any thoughts would be appreciated.

The sparking is normal all the modules need power. Ck this link for parasitic draw test if that is your problem.
http://www.popularmechanics.com/cars/how-to/repair/how-to-stop-car-battery-drains