Yerg

I KNOW THIS IS PROBABLY A BEATEN HORSE BUT ...2002 grand Cherokee 4.0 4x4. It has the dreaded battery drain. I've read all the articles and checked just about everything. New battery, charging good .
I disconnected the negative cable and placed a test light between the negative cable and negative battery post. It lights up. So I pulled every fuse and relay and no change. Disconnected the starter leads, no change. When i touch the positive or negative side post it has a nice spark. What could be drawing this much power. It drains the battery overnight if left hooked up. No after market anything just a stock jeep. ANY HELP IS APPRECIATED

dave1123

Try disconnecting the alternator, all the wires. If you have a door open or the underhood light on, the BCM is still live and drawing power.

SteveMongr

The following link is helpful regarding WJ battery drain.
http://www.jeepforum.com/forum/f310/...ining-1315420/

Yerg

Actually I opened all the doors and flipped the latch. I located it down to 2 fuses. One is the amp radio fuse and the second is the courtesy lights. If you pull both fuses the draw stops. Put one or the other fuse in and the test light comes back on. What do the have in common? Could it be the headlamp switch?

Yerg

UPDATE...Scanner says pcm has internal malfunction. Guess we're starting there..any thoughts

Yerg

Correction ECU internal failure

SteveMongr

Following link shows location of all modules. http://wjjeeps.com/modules.htm

94zj318

The first step I'd do is a parasitic draw test. You disconnect the terminals on the battery and connect them to a multimeter (look up how to do it BEFORE you do it, or else you might mess up your Jeep's PCM (computer)). You'll set the multimeter to measure amperage (DC 10A), and hook the leads up accordingly. Then take a reading of what the amperage rating is with no fuses pulled. To get an accurate reading, you'll want to make sure all doors are closed, and the lighting control stalk switch set to "Off". This is because the lights regularly come on when you have the doors open, and that will cause the amperage rating to change. After that, have a helper stand outside to read the multimeter screen while you pull each individual fuse inside the Jeep one by one, having your helper read the amperage rating out to you with each fuse pull (also, yell out the fuse number to your helper after each fuse pull). If there's a significant change in amperage after a certain fuse is pulled, find out what that fuse powers. That's your parasite (the problem).

dave1123

"Bleepin' Jeep" on YouTube has a very good video on parasitic draw and goes farther in diagnosis than most others.

94zj318

Right, so does Chrisfix. His video was on a PT Cruiser, but everything is universal, LOL.