Cadillac Repair: fuel data center, ohmeter, purple wire

Question
my fuel data center displays a "d" at all times now. I switched plugs on the fdc and ecc when i did the ecc displayed a "d". what else can i do to try and fix it. also what i a bcm connector or bcm and where do I find ct719

                      thanks mike

Answer
Hi Mike, Looks like you have done alittle diagnosis already and swapping the panels was the first step. Too bad you didn't mention the year and model so I could be more specific in my reply.
The BCM/ body control module is another computor that controls certain things and the FDC and ECC are some of them. The BCM is usually located behind the glovebox area and has 2 groups of wires put in connectors so the BCM can be replaced without having a bunch of wires sticking out.
CT719 could be a ppl/purple wire that goes into position B1 at the BCM connector and position V of the FDC. Both connectors have letters cast into the side to give their location. I am useing a 1991 Sedan Deville book to give you this info.
So the next step would be to unplug the BCM connector with the key off that has CT719(you will need a wiring diagram for the year and model car that you have because they all aren't wired the same) and the FDC connector and then take your ohmeter and put 1 meter lead to metal/ground and touch the other to the terminal for CT719 and see if it shows a reading other than OL or infinite. If it does then the wire is shorted/touching metal and will need to get repaired. If the wire is ok then the BCM is bad and needs to get replaced. There was a service bulletin that covered special diagnosis so knowing the year and model of your Caddy then the bulletin might apply and special testing might need to get done. Hope that helps explain things. Bill