Chrysler Repair: Trans Fault Code 720, 731:99 Chrysler Sebring, chrysler sebring, weather seal

Question
I have recently experienced the problems with my 99 chrystler sebring that when i went and had it hooked up to a diagnostic machine at local auto parts store the number and the problems that came up were as follows: The PMC has detected an incorrect gear ratio condition in first gear #P0731, The PMC has received a signal to turn on the "malfunction indicator lamp" from the transmission control system #P0700 and The PMC has determined that a malfunction excists in the electrical circut for the output speed sensor #P0720.  I have never had any problems before today.  The part store has told me to contact the dealership and they are not in today. Can you give me an idea of what the problem may be? Do you think it may be an electrical problem?  Thank you for your time.
Shannon

Answer
Hi Shannon,
Thanks for getting me the description of each of those codes, even just for verification.
The 3 codes are self-consistent and point toward the output speed sensor's signal being at fault. They would cause the 731 and 700 codes. Now it could be a simple wire (there are only two) problem between the sensor and the transmission controller, but it is common experience that the sensor itself wears out. If you have any inclination to replace it yourself you could do with wrench because it simply screws in the the side of the trans that faces the front of the car, at midlevel height, just to the right of the base of the shifter "tower" whose lever is moved when the driver changes the gear selector. You could have a friend move the shifter so you can see what I mean. The sensor has a two-wire plug at its tip held in place by a plastic locking tab that you only need to gently lift with a finger tip and then you can release the plug. For verification that you have located the sensor, the wires' colors should be light green/violet and dark blue/brown. Then use a box or open-end wrench to remove the sensor. there is a weather seal that you want to preserve and reinstall with the new sensor. Apply a force of about 20 lbs to the wrench to loosen and tighten the sensor in place. Then put the plug back on the tip and you should solved the problem.
If you don't feel up to it, maybe you have a friend who with these instructions will do it. The sensor itself costs about $75, and the dealer may add a charge of $100+ (they will want to do a readout, which they will charge for, for example) to put it in which you can save. If it is a wire problem they will probably spend $200 to find it or not, so my theory is spend a modest amount for the part that is the most likely cause of the problem and install it yourself. You won't waste much if you are wrong and can save a good amount on labor; and sooner or later you will need the sensor anyway. Make sure you get the correct replacement sensor for the year and engine/trans combo in the vehicle.
Roland