Chrysler Repair: Transmission wont shift out of 2nd gear: 99 Sebring, odometer mileage, 4 digit numbers

Question
Hi
I have a 99 Chrysler Sabring Convertable automatic. I believe it is a 6 cylinder. I just bought it used and seemed to drive fine yesterday. Today when driving to work in stop and go traffic it stopped shifting gears and wouldnt come out of 1st. I stopped at a station and put fluid into the transmission being it was low. When I started it back up and left it was shifting gears again. Later that day I was driving delivery and seemed to still be working fine except when I came off the highway it gave a hard jerk then wouldnt come out of 1st gear again. I stopped turned of car then restarted and it started shifting again. Then when I started to slow down and then speed back up it jerked and wouldnt come out of first. Can you tell me what is causing this?

Answer
Hi Tonya,
The transmission is behaving in this manner because there is something wrong with its functioning which its electronic controller has sensed as a "fault" which requires attention by a transmission expert. When something like this happens, the transmission protects itself by only driving in 2nd gear which avoids using more parts than necessary. It is called 'limp-in mode'.
The fault is given a code number and stored in the memory of the controller. You may be able to find the number by using the ignition key: turn the switch "on-off-on-off-on and leave on". Then watch the odometer (mileage reading) on the cluster to see if it changes and substitutes one or more 4-digit numbers, which would be the fault codes. It may not do that, but it is worth a try.
If not, then you can go to an Autozone parts store if there is one near you and ask if they do code readout free by means of a readed that plugs in to a socket under the dash. If that isn't practical, then go to an independent repair shop you might trust and ask if they will do the readout for around $40. The most expensive would be go to a dealer who will likely charge $80.
When you get the fault code numbers ask what they mean, what needs to be done and how much it will cost? Then write me back and we can evaluate where things stand.
If there was any warranty implied in the purchase of the car, then just take it back and tell them that the transmission has a fault and cannot be driven except in limp mode.
One last point, it is important the the transmission fluid be called ATF + 3 or ATF +4, or that too can exacerbate the problem. If you added something different then that should be drained out as part of the remediation of the process and new fluid put in.
Please let me know what the code numbers are and we can go from there.
I would also check the trans fluid level again. It may be that you just have a large leak of fluid (that needs to be corrected) as that too will cause a "limp-in".
Roland