newprotest.org: BODY CONTROL MODULE

BODY CONTROL MODULE

March 27, 2011
by: jovial_cynic


In addition to the transmission issues that Dodge Caravans are known to have, having the instrument cluster go out is another common problem which I had the luck of experiencing. And similar to the transmission problem not actually being a transmission issue, the problem with the instrument cluster has nothing to do with the instrument cluster.

On the Dodge Caravans (and many other Dodge vehicles, apparently), the Body Control Module (BCM) controls several functions of the minivan:


Automatic door locks
Battery protection
Chimes
Compass/mini-trip support
Courtesy lamps
BCM diagnostic support
Door lock inhibit
Headlamp time delay
Ignition key lamp
Illuminated entry
Instrument panel dimming
Mechanical instrument cluster support
Power door locks (with/without remote keyless entry)
Sliding door memory lock
Vehicle Theft Security system (VTSS)
Windshield wipers / washers (front and rear)


I read through as many forums as I could to see if I could trace down the root of the problem. If I could avoid buying an expensive part for the van, that would be ideal.

The first thought that was that I'd have to replace the BCM outright, which I could pick up for about $100 on eBay. However, the problems with the instrument cluster not showing anything was intermittent. Sometimes, I could tap on the cluster and it would kick back on. That didn't sound like a computer issue. It sounded more like a loose wire, so I pulled the BCM plugs and checked everything to make sure that there wasn't anything amiss. After that, I pulled the instrument cluster to see if anything seemed loose back there, but I couldn't identify any problem.

After a little while of dealing with the intermittent gauge cluster problem, I noticed that there was also a problem with the heating/AC controls. I could turn the air on and off, but the temperature and direction (face, floor, defrost, etc.) was stuck on defrost. This didn't seem like it was related to the BCM, but the problems started at the same time, so I decided to see if I could find a common ground between the two that could be causing the problem. I was going at this blind, because the wiring diagram in my manual didn't show any common grounds.



Pulling the heater control panel was a matter of removing four screws: two shown above the CD player, and two down below, under a cover above the cup holder.



There are three plugs to deal with. The plug with the 21 pins turned out to be interesting.



Unfortunately, my wiring diagram pin-out only explain what pins 1 through 19 control.



It's hard to see in this photo, but the bottom-right pin was brown, in contrast to the other shiny silver-colored pins. I didn't think much of it, but then I looked at the plug itself.



Yup. The spot that held pin #21 is melted. There is a loose connection at that location, and the repeated arcing heated up the plug and ended up coating the pin, severing the connection entirely. After a couple of minutes of scrubbing the pin and tightening up the plug, I put it back together and my instrument panel worked perfectly.

Weird, right? Why would a break at the heater control have anything to do with the instrument cluster, via the BCM? Wiring efficiency, I guess. Having common grounds across different circuits saves on wires, but it sure make it seems like there are gremlins in the system. On the other hand, it did make it a little easier to trace down the bad ground, because I went into it assuming that the problems were related. The forums I've read on this problem have never linked the gauge cluster and the heater controls. In fact, the responses I read to someone else with the exact problem stated to view the two systems separately, and to start with replacing the BCM. In this case, that wouldn't have helped.
np category: caravan
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COMMENTS for BODY CONTROL MODULE


Amy said:
I'm an art history professor and I'd love to show a slide of your metal laocoon to my class. Is this ok? And could you provide, title of work, date made, and approximate dimensions? Also do you have any higher res images of it? I teach a combo of studio and art history students, and they really enjoying seeing contemporary takes on ancient art. Please email me back - thanks!!
April 24, 2011


kt said:
I happened to take mine apart and the exact same thing happened to us. Same story. I've been looking for replacement pieces, that is near impossible to find. I'm hoping for the same remedy as you found. May I ask how you cleaned the pin? Did you need to buy a new plastic 21 pin cartridge? Thanx
June 30, 2011


Randy said:
Automobile manufacturers have a goal of eliminating the possibility for owners to do routine maintenance on their own cars. Each year, the devise new systems that rely on their in-house dealership massively expensive diagnostics and flashing computers. This means that consumers are completely at the mercy of dealerships to keep their cars running. Unfortunately, mercy is very scares at automotive dealerships and it is common for what used to be simple automotive repairs to cost a small fortune, much to the delight of the dealerships and auto manufacturers. What can you do? Get and maintain a vintage auto. Up until the early 90's, most cars were still fairly easy to navigate and repair without multi-million dollar diagnostic computers. The never the car you buy, the more you can expect to spend on maintenance down the road. You might avoid some of this by letting go of cars once they reach the 5 year old mark as that's usually when most troubles begin. As consumers, we have to pressure car makers to stop making the upkeep of vehicles beyond our reach. Do your homework and do some research. Then, vote with your purchase (or lack of).
October 13, 2011


Randy said:
This is a good thing to check. In may cases, it will not be the pin. Many erratic issues can be traced to faulty switches, physical wire issues, inter-system issues where other computers or components are involved and yes, the BCM itself can actually go bad. It's not as simple as going to the junkyard and buying a replacement BCM. Each vehicle had it's BCM specifically programmed for the unique set of accessories and features that were purchased with that particular vehicle. So unless you manage to find a vehicle with the exact same set of options that yours had, you may still encounter problems. As vehicles become more dependent on sophisticated computer systems, we can expect to see more and more of these problems as vehicles age simply because electronic components age and fail over time especially in humid environments such as most vehicles endure parked outdoors for years on end. Capacitors are often the first to go but any electronic component will eventually fail due to use and exposure. In the case of the common Dodge / Chrylser / Plymouth Minivans, the manufacturer and dealers are enjoying windfall profits by pricing these parts n the stratosphere. Currently, Dodge demands upwards of $800 for a BCM. I'd estimate their cost at this point to acquire these BCM's due to huge scales of economies with these vehicles to be under $30 US. Great for Chrysler / Dodge, not so good for consumers.
April 25, 2012


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