BCM eats PCM, can't reset?


I posted some while ago about a Chrysler Cirrus on which I could not disarm the alarm; after much ado, it’s at the dealer, and the dealer says:

Well, it looks like at some point someone replaced the factory BCM with an aftermarket one (which was not correct in some way). So that needs to be replaced, and it has also “contaminated” the PCM, which now also needs to be replaced. [This despite the fact that no work has been done on the car between the previous “working” and now “not working” states, so it has definitely run fine in the past with all the current parts.]

My question: is this a reasonable diagnosis?

I’m skeptical because I know a little about computers (dangerous?), I frankly don’t follow this “contamination” process. I doubt anyone’s writing viruses for automotive firmware. In the worst case I’d imagine that maybe the bad BCM, out of the blue, writes some setting to the PCM that doesn’t work with this exact car, and okay it dies. But then you pull the bad BCM, and at worst the (correct) PCM should be un-“contaminated” just by reprogramming the flash (or EEPROM or whetever it uses to store its code) with the correct code. It’s obviously writable since the BCM allegedly wrote to it, so it’s not at all clear to me why the PCM also needs to be replaced.

Could someone help educate me on these things? :slight_smile:




Sounds like BS to me.

Time for a second opinion from another Chrysler shop.
Make sure you look up the new and old shops to make sure they aren’t part of the same parent organization.


It sounds like a great one but if the BCM is replaced, yo have to assume that they will try reflashing he ECM before they TIO (throw it out). So far, the story hasn’t ended.