So a while back my dad (who was helping me do a timing belt change) put the battery in with reverse polarity and it killed the BCM. Well i bought a junker bcm off the internet in hopes that I wouldn't need a reprogramming. One of the things I was worried about was the variety of different part numbers Chrysler has out for what seems to be the same part. I can put some at ease by saying the part number of the BCM i pulled off ended in 38 and the one I put on ended in 37. And apart from one thing (maybe) it works perfectly (with no program).

Some things to note:
-Replacement unit was off of a 2006 (same year) V6 (different) Sport (same). All cabin features are the same and all cabin features now work again (radio, lights, chime, keyless entry, rear hatch etc.)
- I had the impression that the body control module controlled ONLY these types of things but the Liberty has its quirks. The oil pressure sensor and possibly the water in fuel sensor are both effected in some way by this module (OPS was confirmed through service manual diagnostics).
- As soon as I replaced my BCM i got a WIF and OP light (that did not go away after erasing with OBDII tool). The WIF was simply because I had replaced my fuel filter head and hadn't bothered to plug it back in (it went away the moment I did that).

I speculate that the BCM is still programmed for the gasser and is looking for a phantom pressure from its old (now scrapped) V6 liberty. I'm not sure on the oil pressure difference between the two engines but I assume they'd be different enough to confuse the BCM. It could also be that the cheapo OPS is out or I've lost continuity but I'm currently too lazy to crawl under with the dmm and start diagnosing.

Any ideas or speculations? Why would the BCM have anything to do with these sensors?

Hope I helped anyone else in such off an unfortunate circumstances. I'm also glad to have a radio, door locks and cabin lights back finally.

I think there is a good chance that the BCM may need some programing to correct the Oil Pressure light...I will see if if I can find the different oil pressure ratings between the CRD and the Gasser.

I am surprised that you did not blow more things up with the battery polarity swap such as the BCM/TCM or blow the "Fusable Link" inside the thick lead from the alternator to the battery!

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2002 Export CRD 2.5 Sport

I'll be taking it in here soon for some programming to see what that changes. Another interesting development is that I'm in part time 4x4 according to my lights

It may have gotten the Tcm a bit. Afterwards I started having the hard shift from 2-3 and delayed shift from 3-4 ( from 35 normal to about 45). It goes away for a bit after I've disconnected negative which says its electrical to me.

This is because the switch on the transfer case that controls the indicator light has either gone bad or has fallen out of sync.


This seems to be a common problem with the 545rfe in the CRD. I dont know what the solution is but its not related to the BCM. It might clear up on its own.

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U.S. Army Retired

I thought the Oil pressure sensor on the CRD sent out either a yes or a no(as in "yes your engine is about to blow up", or "no your engine is not about to blow up"), not an actual pressure reading.

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2006 CRD - GTB2056 turbo by Dieselguy86, Eco Trans Tune, Lift Pump, Week's, HDS Tstat, Racor Filter, ARP's, OME 790's+Top Plate, JBA 2.5", JBA UCA, Moab's+265/75R16, ARB Bull Bar, 4.10's, TrueTracs

I agree with the transmission, more than likely the battery being out for a while made the tcm reset and it will relearn the shifts again.

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2005 kj CRD, samco, suncoast tc, provent, Kennedy lift pump, GDE ECO full torque, 2nd gen filter head, 245/70/16 a/t tires, mopar light bar, fumoto oil valve, OEM Skid Plates, ARB Front bumper and HD OME, tru cool LPD47391 40k GVW tranny cooler (stock cooler delete), FF Dynamics e-fan and shroud, rocker arms replaced, HDS2 190F thermostat.

Well according to the circuit diagrams it is a three wire potentiometer which gives a variable reading according to the pressure.....this is for the CRD! All three wires go to the BCM.


The Gasser on the other hand has a simple ON/OFF two wire switch going directly to ground from the PCM.

So you would need the correct sensor for the correct engine, correct wiring loom and correct connectors for your application! but seeing as only the BCM here has been replaced I would definitely expect that the BCM would need re-programming

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2002 Export CRD 2.5 Sport

I would agree with both of these comments. My BCM was toast a few years ago, and though it messed up many things, it had no impact on you two issues. My BCM was replaced by a dealership that didn't program it correctly, and I had all sort of buttons not working, but then it was reprogrammed, and everything was good again.

As for your hard shifting, I had the hard shifting for awhile this summer after towing a trailer off and on for two months, but then the problem seemed to correct itself after I stopped using the trailer. Is it possible that the learn feature just needs some time to adapt?

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2005 Black KJ Sport CRD,
GDE Full Torque ECO TUNE, GDE Transmission ECO Tune,
Samco British Racing Green Hoses
Build Date 1/05
200k miles.
Original Owner