Chrysler Repair: transmission wont shift out of a low gear, transmission shop, logical approach

Question
i own a 1993 crysler lebaron. it has 78 thousand miles. i have never had a problem with it, till the other day. i was driving it on the highway and it seemeed to be stuck in first gear. the engine was running high, but the car would't shift up. nothing else seems to be wrong. is there somthing i can do to fix this?

Answer
Hi Ina,
That sounds like the behavior of a 4 speed automatic, which has gone into limp-in mode, which the transmission will do to protect itself when it experiences a problem. There is a blue 6-pin connector beehind a small door at the very left hand end of the dash which gives access to both the engine and the transmission controllers' memories by means of a readout box.
An independent transmission shop with a reader and a "data link connector" to mate with the connector under the dash can readout the fault code number(s) stored in the memory that is going to explain what is the problem. It is a two-digit number in the Chrysler system of transmission codes. Make sure that you get the transmission fault codes, not to be confused with those for the engine.  Once you get the readout, ask for the numbers, what they mean and what they propose to do. Then write back and we can compare it to the shop manual.
Do check the transmission fluid level to verify it, and if any is needed only use ATF +3 or +4, never Dexron.
This is the logical approach to the problem.
Roland