Chrysler Repair: OBD II communication failure, drb iii, plymouth voyager

Question
My 98 Plymouth Voyager passed smog easily yesterday except for a MIL/Check Engine Light Test due to OBD Communication Failure. In the past, I read my OBDII codes at Autozone and some readers would work, while other readers would not. It will not pass smog at this Test only station without them reading the OBD results.  Should I take it somewhere else? Does Plymouth have a unique setup that only the dealer can read?

Answer
Hi Rob,
There is nothing I have heard about Plymouth (or any other of the mini-van marques) regarding this being a generic problem. I checked my '98 body diagnostic procedures manual and it suggests a couple of approaches;
1. go to the data link connector under the dash and verify that pin 4 is well grounded and that pin 16 has 12V on it (if not check the fuse labelled IOD in the powerbox under the hood). Let me know if either appears open or flaky and I can describe the wiring to those two pins. We also can check the wiring of the data bus pins to the network.
2. the other is to try serially detaching each of the modules that are on the data bus, and then see if the reader recognizes they are detached. If not, then the specific7 detached module is likely needing replacement. The order of testing is:tcm,pcm, infinity radio(if equipped), compass/mini-trip (i.e),instrument cluster,anti-lock brake module (i.e.), HVAC control, bcm. If all are recognized then replace the reader cable or the reader.
I readout with the Chrysler DRB III might be the fastest way to id the problem but there would be a charge of probably $80 or so for that. If you have a volt-ohmmeter at least check pins 4 and 16.
Roland