1996 Town and Country LXI with VTSS alarm system.

I bought my van from an owner who gave up trying to get the gauges to work reliably even after replacing the BCM. I studied the forums and found the cluster soldering repair, which fixed things for about 9 months. The gauges started failing again so I did the usual fixes like battery disconnects, and IOD fuse pulls, but that only fixed things for awhile. I bought another cluster from a junkyard, and soldered it, and that also worked for awhile, but not always.

Now things are worse. The gauges are dead and none of the tricks are working. The CCD bus voltage is only 0.5 volts on both sides, instead of my usual 2.1 volts (I don't seem to get the proper 2.5 volts). I have tried all sorts of things like replacing door switches for the VTSS, and I even pulled the BCM and sent it away to have it checked and repaired, but that was an expensive disappointment, since nothing improved when I got it back.

I have been disconnecting modules and noting ccd bus voltages. If I pull the BCM the voltage goes up to 1.5 (dancing), and if I pull the PCM or CAB the voltages might vary 0.25 volts, but I can't get up to the 2 volt level where the gauges would light back up. Does anyone have any oddball fixes that worked for them? I've got to try something. Thanks.

 

Disconnect the overhead console.

 

Thanks for getting back to me. I tried that, as well as every other module on the ccd bus. The bus is made up of the BCM, the instrument cluster, the PCM, TCM, radio, hvac controls, airbag controller, antilock controller, overhead console, and the data link connector where I check ccd bus voltages. You can't disconnect everything at once, since then there would be no source of voltage or termination, so I left a few modules connected, and added or subtracted one or two at a time.

If the BCM was not connected, and the PCM was not connected, I would get 1.0 volts (dancing readings as the bus communicated). Adding back the PCM would get the voltage up to 1.5 and then adding back the BCM, would pull the voltage back down to 0.5. I am concerned about why the bus is not the 2.5 volts it should be.

I've had the PDC (power distribution center) out and looked to see if any wires were damaged by battery acid. All looked OK. Anyplace else I can look - fuses, wires, or grounds - that have proven to be a trouble spot for somebody?

 

Just a heads up for anyone in the future with similar symptoms. After checking the wiring harnesses for chafed wires or corroded grounds, and finding nothing amiss, I bought another BCM on EBAY and tried it out. Everything suddenly worked. My ccd voltages were 2.5 volts, instead of the 2.1 volts I had always gotten on my old BCM. My guess is that the old one worked, but badly - just enough to appear fine for awhile, and then to fail intermittantly. Just happy to have the van back again.

 

I've read of a similar problem, voltage on CCD bus signals degraded. In that case bus termination resistors or pull-up resistors in the BCM were failing. From the description they're an easy replacement (if you can identify them). They're only few cents at an electronics store.