Chrysler Repair: Chrysler T & C 1997 service engine soon light, obd ii reader, kurt hoffmann

Question
Hi Roland, I have a 1997 Chrys. T & C van w/3.8 litre V6. I ave 170 k miles on the van. At 135 k, I had a new Chrys.replacement transmission installed at a local reputable trans. shop. I can't remember for sure, but the "service engine light" either was on before or came on after the new trans was installed. The dealer told me it needed a new computer, wiring hareness and trans. control module all parts very expensive). The car fails Calif. smog because of the engine light. I took to a private shop and they installed a new computer. This did not solve the problem. Scanners don't seem to be able to communicate with the cars computer. Light was off for a while but is back on now. In addition, after the new computer was installed, the lights on all the cars climate system (on dash below the radio)were blinking. Now, some son't light up when engaged, and the a/c and recirculation buttons are still blinking. Sorry this is so long...any suggestions? thanks,  Kurt Hoffmann  

Answer
Hi Kurt,
Any problem with communication to the engine controller is challenging. When you say the scanners 'don't... communicate' does that mean that absolutely no response from a query or do they get a specific P plus 4 digit code that has that meaning? If the latter, what is the code number?
Your van is right at the cusp of the phase in of the OBD-II diagnostic code system. There is an outside chance that it might be able to read out some codes using the ignition key:
Turn it to run,off,run,off,run and leave it on run, accomplishing this in 5 seconds or less. Then observe the check engine light to see whether it begins to flash, pause, flash, pause, etc. Count the number flashes before each pause if you get that sort of behavior. Then write back and tell me the numbers of flashes before each pause.
If you can't get any codes that way, and you can't get any codes from an OBD-II reader then the wiring from the test socket to the computer will need to be checked. I don't have the troubleshooting manual for the van but rather from the contemporary car lines, and if you could examine the wire colors of all the wires on the 16-pin under dash code reader plug I could see if they are the same as in the car lines and then we can figure out where they go to and check each one for continuity using a continuity testor.
On the A/C heater control unit, those blinks are another form of self-diagnosis restricted to that unit. If you can tell me which push buttons the unit has I might be able to give you a procedure to test that unit, based on the car-based ATC unit test procedure. Does the heater system show any problems?
I'll respond to the All Expert site and to your email address. In order to keep a working record of this exchange, please copy this and your original question back into a new question at the site, after giving them the correct email for you.
Roland