Need help with BCM testing!

Hi guys/gals,
I posted a question on here about a week or so ago in regards to parasitic draw. I have a 1996 Jeep Grand Cherokee 4.0L with a battery drain issue. Through my initial testing I narrowed the issue down to the 50 amp fuse #11 in the power distribution box under the hood. I checked the wiring schematics for this circuit and found it goes to the junction block. I checked each fuse in the junction block for any Voltage Drop. I found fuse #7 for the cluster was showing .22mV where all other fuses where showing 0.00mV as they should. I unplugged the cluster thinking it was a common failure part and there was no change. I installed a home made fuse buddy in place of #7 fuse in the junction block and used my vantage ultra with a low amp clamp set to low 20 amp setting. The reading was .13amps or 132mA (the vantage was in auto range mode). I did some more digging and found that when connector "B" white 24 pin at the BCM is unplugged from BCM my draw goes to .04amps or 53mA and I confirmed no draw by installing #7 fuse and doing a VD again and found 0.00mV as i should. My issue now is how do i verify if the BCM is at fault or something on the connector "B"? I checked by unplugging headlamp switch, multi function switch, light sensor, rear wiper switch, and no change. Customer has since informed me the dash lights would flash/flicker constantly while driving. Nice time to tell me this....grrrr. Anyway, I unplugged everything i can see that would relate to the dash lights and had no change. I assume this may be a result of drain issue and not the cause! I am stuck...please help!!!!! Thanks for reading, Jeff

Hey Rottiguy76! The only thing I can think of beyond what you've tested already is a possible network issue, causing the BCM to stay powered up. Looking at the diagram, I see an overhead console, the automatic temp control, radio, vehicle information center, driver door module, passenger door module, memory seat module and PCM on the CCD network. Any one of those modules that is transmitting with the key off could cause the BCM to never power down.

The diagrams I have here at home don't ID the BCM connectors with letters, just C240, C241 and C383. Can't tell if your connector B has the CCD network on it or not. Anyway, I was thinking you could get the draw to start up again, and scope the CCD pins at the BCM for activity (after a power-down period of ~45 mins). If you find some, then start disconnecting these other modules until the activity quits. If you find no activity, then I'd say that's another strike against the BCM.

Hi..

I just had a jeep with some of the same issues, you just stated that the customer told you that the dash lights go on and off for no reason, Jeep has a problem with the TIPM I changed the TIPM and all is well in jeep land.
TIPM big fuse box under the hood driver’s side, NOTE remove the battery first..

Doc n2m

For reference, I found this little tidbit:



Not exactly a known good waveform, but it seems like 2.5V is neutral for the CCD bus.