Chrysler Repair: 2001 Dodge Grand Caravan

Question
Hello Mr. Finston!  I have a 2001 Dodge Grand Caravan 3.3L gas/Flex Fuel vehicle.  I am the second owner of the vehicle, (my Grandparents being the first owners) which has NEVER had any mechanical issues.  I have had regular maintenance done on it and it has never failed me.  Then all of a sudden the check engine light comes on, and it is jerking on down shift I would say probably 2nd gear. Almost at stop???  I took it to Auto Zone to have a diagnostics check.  The guy said that the speed sensor needed to be replaced. so I bought the part and replaced it.  Everything was good for about a week, and then it started again. This time it was the other speed sensor. So I bought and replaced that.  Same thing... Everything is fine for about a week, then all over again.  So, I exchanged both sensors under warranty, and replaced them at the same time.  This time it was about two weeks.. and here we are again. So now I am here!  I took the codes that they gave me from Auto Zone, and these are them: P1790, P0715, and P0700.  I have no idea what they mean, and I am in desperate need to figure out what is wrong with my vehicle.... Any help would be most appreciated!!! Thank you

Answer
Hi Rebecca,
The 0700 is just an 'alert' that other trans codes being also noticed, but if it were there alone then it may indicate that there is a problem with the transmission control module itself.
That is an expensive part and I would not get into that without further code revelation.
The 1790 means the problem appeared immediately after (within 1.3 seconds) of a shift.
The 1715 means that the comparitive speeds 'seen' by the two speed sensors are not correct when comparing between the two readings given the gear that is in use. If that were true and accurate it would say there is some internal transmission "slippage" that requires a rebuild. It might instead be an issue with the input speed sensor function, or the harness/connector of one of the speed sensor could be 'open' or short-circuited. Another possibility is a malfunction of the transmission control module.
My first inclination would be to verify that the two signal wires, one for each sensor, that connect to the transmission control module's plug are patent and are not shorted together or to the ground wire which is the third wire.
The dark green/violet "ground" wires on pin 1 of both speed sensors' plug is supposed to be connected to pin 13 of the transmission control module's plug.
The dark green/white wire on pin 2 of the input speed sensor is supposed to be connected to pin 52 of the tcm plug and the dark green/brown wire on pin 2 of the output speed sensor plug is supposed to be connected to pin 14 of the tcm. Those connections should be tested and the wires gently flexed while the measurement is taken. Also verify that the two wires for each sensor are not shorted together while disconnected from the sensor.
Other than those measurements the other possibility is that the transmission control module itself is faulty, but I would not opt to replace that right now.
So start with that and see whether something is revealed as being wrong. There are many specific codes that might appear and give a better idea of what is really wrong.
Roland