QuestionQUESTION: Have a 1997 Chrysler Sebring Convertible JX with a 2.5 V6.
Have had engine cooling fan (won't shut off) and A/C (clutch won't engage) issues. Narrowed down to the BCM. Found one with same number except for last character. Went from "AB" to "AC", which I was told by a dealer that it was just the software revision.
Replaced the original BCM with a used one. Car started right up with no issues other than I lost my keyless entry and the used BCM had 50K more miles. Fan and A/C issue still existed. Since it did not fix issue I put the original BCM back in. After re-installing original BCM, the engine dies after 2-4 seconds like it's out of fuel but my keyless entry worked. Checked all fuses and relays but everything looks good. Put used BCM back in and runs like a champ. Went to unlock door next day with the key and alarm started going off. Will not stop when car started. Unhooked battery to shut off alarm.
Would like to put original BCM back in because used one has about 50K more miles on it and I would like my keyless back. Any suggestions?
ANSWER: When you change out a BCM or PCM in a vehicle that has a security system you have to program those two unit such that they recognize one another as having the same VIN. That can only be done using a Chrysler DRB III diagnostic readout box at a dealership. I am surprised though that they told you the engine problem was the BCM (body) rather than the (PCM), but the new problem you are experiencing would be the same either way. Maybe you meant you changed the PCM?
Similarly, the keyless entry settings are stored in the BCM so if that is changed the DRB again has to be used to program it to recognize the fob unless you happened to get the fob for the vehicle where came the replacement BCM. So it is likely that a dealer or a shop with an advanced box that has this capability will have to do it.
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QUESTION: I did replace the BCM. Chrysler dealer told me it was plug-and-play. Another person I asked told me that when I replaced the BCM with a used one, it basically reprogrammed the PCM to look for the security settings of the used BCM and cannot be reversed. I have access to another PCM the has the same part number as my original. If I remove the used BCM, install the used PCM, and then re-install the original BCM, would the used PCM then be reprogrammed by the original BCM back to normal? Kind of confusing and hard to follow, but I think it makes sense if the BCM will reprogram a PCM.
AnswerHi Dan,
I don't think so...the manuals speak of the intervention of the DRB being brought to bear on the situation when one or the other is replaced. I don't think one can be expected to program the other. I don't have personal experience because I don't have a DRB III, just 'book-larning'.
The impression I get is that while the pcm and bcm do obviously communicate with one another, neither has the ability to change the other's settings. That can only be done with a DRB.
As I understand it, you want to use the original BCM with a new/used PCM. According to the '98 PCM manual, if the PCM is changed and you don't update its VIN and its recorded mileage on the vehicle, then a diagnostic trouble code will be set in the ABS system (if equipped) and in the airbag system. That may not prevent you from driving the car but it will probably turn on the warning lights. A DRB is needed to do the updating. The remote will likely work with the old bcm installed. If you have a sentry key immobilizer system (the key with the bulge) then you will likely find that the pcm will not be accepting of the key and the engine will shut down after 2-3 seconds, thus requiring the DRB to correct that problem.
