Chrysler Repair: Oxygen sensor, and Map sensor diagnosis problem, plymouth neon, snail mail

Question
I have a 1997 Plymouth Neon 2.0 sohc, the MIL light came on a couple of weeks ago with no symptoms. The scanner showed a lean code and a shorted downstream o2. I replaced the sensor with a dodge sensor. The light returned, this time no lean code, but the shorted o2 returned with a no activity code for the downstream. I have key power hot, ground from the pcm, and body ground is good. I am showing no activity on the input to the pcm. But i seem to have good continuety from the pcm to the pigtail for the sensor. Should i suspect a bad sensor first or try to run a new wire, or possible suspect pcm? I've ignored the prob til now and now have a Map sensor code showing overboost is above range. Could they be relate?

Answer
Hi Seth,
I have the powertrain trouble shooting manual for that engine (1998 version, but close enough). However I haven't worked on that one yet. If you could tell me exactly which trouble codes you have, I could take a look at the instructions for the various codes, or better yet copy them from the manual and snail mail them to you. You seem to have a good knowledge of the engine, and maybe just having the specific trouble shooting  instructions would get you to a solution.
Roland