Parasitic Drain

Hi guys/gals,
I have a 1996 Jeep Grand Cherokee 4.0L Limited with a battery that goes dead after sitting for two days. I am horrible at electrical diagnosis! I subscribed to the premium channel here and purchased the book to follow while watching each video. I have a basic understanding of testing for a parasitic draw. I have a good battery with 12.62V and clean terminals! With a low amp clamp around the negative cable and the leads connected to a vantage ultra on the low amp 20 scale, I am reading .32 amps. (I forgot to write it down and that is what I recall seeing sorry) which led me to believe I have an issue. I then did voltage drop across the fuses in the power distribution center. The 50amp fuse, (fuse #11) is showing .19mV drop. Every other fuse is showing .00 as they should. I traced the circuit to the Junction Block in the right hand kick panel. Without opening any doors i climbed through the window and bent myself in a way that i could do VD across the fuses. Fuse #7 (20A) is also showing .19mV drop. The BCM and the auto headlamp light sensor/VTSS Led are the only things alldata is showing on that fuse. I pulled the connector for the auto headlamp light sensor/VTSS Led and the VD is still present. I had previously removed the knee bolster on the driver side so I was able to pull the plugs on the BCM....which led to my VD to go to .000. This is where I need help! First....according to Power Probe fuse charts, a .2mV drop across a 20amp mini fuse is equal to 62mA of current flow. Am I correct in thinking this is not within spec? If so, how do I test further to verify if the BCM is at fault or if I have a component connected to the BCM that is at fault? I really wanna learn to do this kind of work because I enjoy the thrill of the hunt if you will! I am just starting to dive into this leg of auto repair and have lots to learn so please be kind!! I spend most of my free time watching SD's videos and case studies, but free time is minimal at best right now. Thanks for any help! Jeff

Good start!
Make sure you "zero" amp clamp before use. Then just pull that suspected fuse(s) and watch the current draw. Do you get acceptable current draw when you remove 50A fuse?
Here is what mitchell thinks of your circuits.

I would look for any aftermarket accesories on the vehicle you may not be aware of particular a hidden anti-theft system but any aftermarket equipent such as GPS or ICE or phone charger could be the drain.

I tend use voltage dop accross a a fuse only as an indication where to look, once a circuit is under suspiscion I usually put an ammeter in the circut to measure the current directly using a Fuse Buddy or similar.




Your fairly 0.32 amp draw is large parasitic drain might not be the whole problem
As a rull of thumb a battery will start a vehicle on 50% charge according to the battery manufacturers listings for models where I am in Europe a Grand Cherokee should have a battery of between 74 and 88 amp hours capacity when new. A 0.32 amp draw over 48 hours is a fairy hefty 15 amp hours but that shouldn't be enough to cause starting problems until the vehicle has sat unused for 4+ days. I suspect your battery may have taken damage through repeatedly slow discharged and followed by rapid recharging when the engine starts..

Hi…

I see that you are on the right track, lets get into it a bit deeper, you found the you have draw on the 50 amp fuse, ok lets look the circuit that was provided by (Borntoroll) .
The 50 amp fuse is showing power and all other you tested are at 0 so, lets just focus on the 50 amp fuse. look at the diagram the 50 amp supplies power to 4 other branches each has a fuse . you can un plug each one and watch your meter at the 50 amp fuse and see if you have 0 draw when you see that you found the circuit at fault.
Now you need to do the same thing with each item that fuse powers, un plug each thing one at a time until you find the problem part.


I would start with the instatement cluster as there are known for doing this …


Good luck

Doc n2mx

Thank you for your help! I unplugged Instrument cluster and draw was still present. I am getting a VD at fuse #7 fyi. I unplugged the auto headlamp sensor and no change. I unplugged BCM and that is when VD/draw went to .000 as they should. So my issue is with the BCM or something attached to it.

Yes see what is in that circuit and do the same unplug each and look to you see 0.
you get the idea , now the BCM could be the problem so beware...

does your car have the amplifier? like in the diagram?

I believe the amplifier was part of the factory stereo head unit which has been replaced. I am planning on unplugging the connector at the aftermarket stereo and checking my draw. Unfortunately I have to work outside and we are expecting heavy rains for the next few days so I wont be able to do much until it stops. Will keep everyone posted! Thank you thus far for your guidance!

The latest test results are as follows......
Fuse #7 in Junction Block removed and replaced with home made fuse buddy jumper. Low amp clamp around wire of fused jumper. My draw is .06Amps with BCM totally removed. One at a time i plugged in connectors...Connector "A" (Black 24 pin no change....second connector 14 pin black connector no change....final connector "B" (White 24 pin) reading jumps to .14 Amps. My issue is something on one of the circuits in the white 24 pin connector at the BCM. Is there an easy way to eliminate or pinpoint which one without disconnecting 16 different possible devices? I like to try to work smarter and not harder unless there is no other way! Thanks for the help thus far!!

I did not dig very deep into the diagrams on this one but I have seen a few vehicles with the rear wiper causing a battery drain the rear wiper motor has power going to it all the time to allow it to park. If it can not go to full park position it will keep power on and continue to attempt to go to the park position and drain the battery. Just something you may want to check I have had a Lincoln Navigator and a Chevy Equinox that had a battery drain and it was the rear wiper causing it sure will not hurt to check it.

Rottiguy76 wrote: The latest test results are as follows......
Fuse #7 in Junction Block removed and replaced with home made fuse buddy jumper. Low amp clamp around wire of fused jumper. My draw is .06Amps with BCM totally removed. One at a time i plugged in connectors...Connector "A" (Black 24 pin no change....second connector 14 pin black connector no change....final connector "B" (White 24 pin) reading jumps to .14 Amps. My issue is something on one of the circuits in the white 24 pin connector at the BCM. Is there an easy way to eliminate or pinpoint which one without disconnecting 16 different possible devices? I like to try to work smarter and not harder unless there is no other way! Thanks for the help thus far!!

We need to be careful about this test. The 24 pin connector may contain the main power and ground for the BCM, so this does not necessarily mean our problem is within this connector. Make sense?
Let me look at the BCM diagram and see if we can find some direction. In the mean time, you have an inductive amp probe that you could go around each wire and test.

97 Jeep ZJ LImited 5.2
Same issues. Erratic gauges, lights door locks and an eventual stalling (had to get towed home). The parasitic draw still exists as I let the car sit for a few days.
I don't throw parts at what I think is the propblem, however, I did replace the door bushings as the door would drop when opened. I also replaced the LF and RR door lock solenoid (they failed).

The FSM shows that the 50 amp fuse feeds Circuit breaker2 in the junction block, fuse 7 and 8 and if I recall fuse 9. Fuse 7 (20 amp in the Junction Block) are on the same circuit as the Instrument cluster, BCM, anti theft arm light, Auto headlights, diag connector and radio amp. Fuse 8 controls the trailer tow, rr wiper motor and lift glass.
I've cleaned grounds, tested sensors, fuses and relays and everything still seems to point to the BCM.
In other searches to this issue on Jeep related forums point to anywhere from, broken wires at the door hinges, tailgate and lift glass switches, power door lock modules. I would isolate those again to be sure.

I am at a point that I think the BCM is the culprit. What tool are you using to diagnose the BCM. The Factory manual seems to show the DRB III (Chrysler diagnostic tool is needed for the BCM test). The DRB is also needed to reprogram the a working BCM. Unless there is an alternative, it looks like I may rent a DRBIII or if I can get one to pay for itself, buy one, used. Keep me posted and I will do the same. I'm new here, so I apologize for the long message.

If you unplug the other 2 connectors on the bcm and the draw is still there, then the problem is without a doubt an issue with the wires on your 24pin white connector. On the diagrams provided, what connector # is it?

To pinpoint the bcm being the problem, leave the connector plugged into bcm, then you would have

• disconnect all components from that harness
• Check amperage one by one as you isolate components
• If draw still exists, unplug bcm connector while all components remain unplugged
• Check all wires for continuity to power or ground (there should be none if all wires are able to be isolated)
• If no shorts are there, it's the bcm.

Rottiguy76 wrote: My draw is .06Amps with BCM totally removed. One at a time i plugged in connectors...Connector "A" (Black 24 pin no change....second connector 14 pin black connector no change....final connector "B" (White 24 pin) reading jumps to .14 Amps.

Ok so you have to be cautious about your results, as you're working your way back to the white connector, leaving the other connectors plugged in. Like I said, if draw is there with only the white connector plugged in, you have it isolated.
Fuse 7 is a power input to bcm that could leave through the other connectors to a component not on your white connector..

Redo the test, but remember to power the vehicle down before you take measurements. Roll the windows down, latch the doors, go ahead and unplug the other 2 bcm connectors, get your fuse buddy installed along with test equipment and wait 30-45mins. See if the draw is still there. If not plug in the other bcm connectors, wait for power down and check the draw again.

The process is meticulous, but necessary. Good luck

Here are the connector pinouts from the FSM. Hope this helps anyone.