QuestionQUESTION: Hi, I have an '01 LHS with a bad BCM (stereo dead, climate control freaked out, NO BUS messages, all up to recently have been cleared by power drain, now the stereo won't come back). I have a dealer who can order one, and think I have located it behind the fuse box (that's my first question, am I on the right spot?). How tough is it to replace? Are there any "step by steps" I should be aware of? Is this possible for a decent shade tree mechanic?
thanks,
dave
ANSWER: Hi Dave,
It is not a complex process to remove and install the fuse box (called the junction block)/bcm unit, and then to separate the bcm from the block. *The one 'trick' is that when you first turn on the ignition to start the car after the bcm is installed you want to wait for at least 15 seconds before trying the starter to allow the bcm to communicate with the pcm to learn the VIN. But you do have to have the vehicle theft security system 'enabled' using a diagnostic readout box III at a dealer, if you want to keep that feature. I would be interested to know what the dealer charge for just programming the new DRB, and what it would be to do the removal and install as well. I can't see how the mechanical issues in removing and installing should take more than an hour.
That latter part looks pretty simple: disconnect the battery, remove the end cap of the dash, disconnect a couple of screws that hold the lower dash panel and then pull rearward to release the clips and then disconnect cable from hood release handle and wire from deck lid release, remove the knee blocker, remove the under-column air duct(s), remove four screws that hold the modules, disconnect wire harness connectors from the junction block and the bcm, remove the module from the mount, remove bcm wire connectors and rke antenna connector, and take out the module entirely. Then you remove the three screws that attach the bcm to the junction block and slide them apart (the two are electrically connected at the interface) and you remove the three screws for the rke module and transfer it to the new bcm. Then you reverse the process.
That is an outline of the process. Talk it over with the dealer.
Roland
PS:I have modified my answer from how I had it originally. I found the procedure for installing the BCM for the '01 LHS and it indeed appears to be the case that you should be able to install it yourself and start the car, but then go to the dealer to 'enable' the theft security system using the DRB III.
---------- FOLLOW-UP ----------
QUESTION: Hi Roland, thanks for the answers on the BCM, you were dead on. The new one dropped in no problem. Now I'm on to the next challenge.
Long after the BCM started having problems, and before I put the new one in, I started having battery drain issues. Recently, it took just about a day to render it useless (down to 5-6vdc). I was hoping this was a short in the BCM, but no, it's still happening. I've narrowed it down to one fuse, #7 on the end panel, labeled Illum Lamps/Park Lamps.
If I leave that one disconnected, the battery holds. Putting an ampmeter on it, it's a little weird. It'll show .55 to .68 draw (depending on where the battery is), for about 3-5 seconds, then drop quickly to zero. Almost like a capacitor charging. If I pull the meter off, then back on, zero, unless I wait a couple of minutes in between, then it does it again. It's not like it's a steady draw. I'm trying to figure what on that circuit would cause that.
Have you seen this before, or have any ideas I could try?
thanks again,
dave
ANSWER: Hi Dave,
There are three circuits that draw on fuse 7: the park lamp relay both coil and output current) and all the external lights except the headlamps (and if you have the headlamp leveling feature that too is involved, though I don't know what year that came in (somewhere between '99 and '04), the instrument cluster, and the high beam relay actuation coil. You could try pulling the relays one at a time to see if the current draw disappears, and if not then the cluster is using the current for unknown reasons (perhaps to store something in its memory, if it has one).
So try pulling the relays and see what happens both to the measured current draw and also to the overall battery run down. Once you figure out which we can think about what might be doing it.
Roland
---------- FOLLOW-UP ----------
QUESTION: Okay, this is getting weirder. I pulled all of the lights related relays, no effect. The draw remained constant. The relays are labeled Fog Lamp/Headlamp High/Headlamp Low and Headlamp Park. What's weirder is I think I found a second problem. I rechecked two underhood fuses that I had seen minimal draw ( <.05 amp) before, and one of them is now consistently drawing over 4.5 amps. I swear I've checked this one a half dozen times before. That fuse is underhood, labeled 30amp "Stop Lamps". If I pull the dash fuse #20, the only one labeled stop lamps, the draw continues.
The first problem is still there, with currently about a .70 amp draw across dash fuse #7, like we talked about, and now this new one is there. I can't see a light on anywhere, and I'm starting to wonder if someone is sneaking into my garage and tapping resistors in just to see if I'll go nuts.
Please tell me this doesn't sound crazy.
AnswerThat 'stop lamps' 30 amp fuse is also known as fuse I. It does power the anti-lock brakes via fuse 20, but it also powers a bunch of courtesy lamps (the M1 circuit in Chrysler engineering parlance) via a paraller feed to fuse 19. If you pull fuse 19 that will cut out the draw on fuse I which is probably what is draining your battery. Basically you have a courtesy light 'on' all the time that you aren't aware of: the most likely are the glove box lamp or the trunk lamp. OR you could have had a door open when you did your measurement so that what you were reading was all the courtesy lamps ablaze!
As for the original observation:
The 0.7 amp draw is possibly then the instrument cluster, but that wouldn't run the battery down the way you described. You could unplug the cluster to test that theory. The 'ignition off' draw is supposed to be around .05 amp. for the whole car after everything has has a chance to settle down. The TCM by the way will normally draw 0.5 amp for about 20 minutes after you turn the ignition off, so that might be the cause of that too. So see what happens after about a half hour of waiting around.
But if you didn't have the door open, it could be your trunk light is 'on' intermittently for example due to a flaky/mis-operating switch.
Roland
