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ECM <--> BCM PCI comm question

2K views 6 replies 3 participants last post by  kevinfish 
#1 ·
Hi everyone:

Can anyone tell me if the PCI from the ECM to/from the BCM (pin 1, C3 on the BCM) is supposed to be bidirectional?

I cut the wire and I can see data trying to come in from the ECM to the BCM but nothing trying to come back from the BCM to the ECM.

Or do I have a bad BCM?

Also, if I have to replace that, is that something a reasonably equipt shop/scantool can reflash with my VIN and mileage?

Is there anything else they'd need to flash it with?

Our local Mopar dealer is no help at all.

Thanks,
-Kevin
 
#2 ·
Depending on what car and trim level you have...

You might be better off getting an ECM and BCM pair from a junkyard car. Thats the cheapest method. No programming needed, only issue will be the mileage will change.

Now, if you find a dealer that can program the new BCM you could go that route but its more expensive as you know and you gotta find a dealer that will even do it for you.
On older cars, there were several wires and the BCM acted like a splice connecting all them together. So in your case you may have that setup and it may be normal.
After the 02 year when they combined the ECM and TCMs together is when they changed this.

Sent from my SM-G975U using Tapatalk
 
#3 ·
oh yeah, I forgot to mention I have a '99 w/a 2.7 and no SKIM.

According to the '00 schematic I'm reading I have the older style cuz all the PCI comm seems to come into the BCM and then from there goes to the diagnostic data port.

The question is, if I break that line between the BCM and the PCM shouldn't I see attempted communication coming from both sides in a key on engine off configuration? Cuz right now I'm only seeing it come from the PCM side and nothing from the BCM side (plus when I do the keydance I don't get any trouble codes but it the odometer just goes back to showing the mileage) and that is what led me to think that there was a comm problem between the BCM (that it is my understanding displays the codes it gets [mostly] from the ECM and to poll the various modules to send up their codes when the key is so "danced").
 
#4 ·
Are you still dicking around with the car with the "Bastardized" 2001 engine wire harness?
 
#5 ·
Are you still stuck on that? I've verified 100% that the wiring harness has been successfully converted to 1999. Every contact has been continuity checked to only go where the schematics say it should go and no other contact.

Please don't comment if you don't have anything constructive to contribute and you don't have the answer to my ACTUAL question.
 
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