Chrysler Repair: BCM and PCM: can one cause the other to fail? Or is this a cover-up?, transmission control module, body control module

Question
I recently took my car in for repair because it went crazy and did things on it's own and wouldn't start. The dealership that i took it to said they called Chrysler and they told him it sounded like the Body Control Module. I paid to replace that and it still wouldn't start. They then told me that they again called Chrysler and were told that the bad BCM had made the PCM go bad. I picked it up today and now the wipers aren't working they said that maybe the wiper motor froze up or maybe a wire isn't connected correctly. They have had this car for a month and it's still not right. Is the dealership right about the BCM making the PCM go bad?
thanks mike

Answer
Hi Mike,
That is an interesting question. The PCM and BCM are networked with the air bag module, the instrument cluster, the transmission control module, and maybe other units depending upon how the car is equipped. They share two wires that carry a bias of 2.5V + and - along which digital data are transmitted. I don't see a basis for how one unit's failure would damage another unit. The failure of one unit can shut down this "CCD bus" system, but I have never seen a history where one part's malfuntion did further damage to another part of the system. I believe that the pcm was the only part that was bad, and they just replaced the wrong part and charged you for it nonetheless.
I would go back to the dealer and request that they reinstall the original bcm and see if the car will still start and operate, and if so ask them to refund the labor charges and part price for the bcm. They should have given you the old bcm and pcm by law (at least in many states) so you can either give them the original bcm to try that while you are there to inspect the result or call you when they find your old bcm and allow you to attend this test of the original bcm. I believe there is a good chance that the bcm was unnecessarily replaced. If you can't get satisfaction I would try the Chrysler regional service rep and if that fails small claims court. They should not be able to charge you for a repair that does not repair the problem, only for the pcm replacement which did repair the problem.
The wipers are controlled by the bcm so the dealer should be responsible for correcting that problem as well because the wipers worked before they removed the bcm.
I would be firm about correcting this botched repair job. If they want any kind of reputation and to avoid a small claims court appearance they should be willing to negotiate restitution. The fact that they called Chrysler is an indication to me that they don't have a competent mechanic on the premises to deal with this sort of problem.
Please let me know what you can accomplish in getting satisfaction.
Roland