P0715 - Input/Turbine Speed Sensor Circuit Malfunction
P0720 - Output Speed Sensor Circuit Malfunction
P1899 - Park/Neutral Position Switch Stuck In Park or In Gear
You have fault codes directing you to the circuits that need to be diagnosed. Don't go looking for other unrelated stuff. The first concern is it is very unlikely you have three sensors that failed at the same time. Instead, look for what they have in common. In this case that is the wiring harness. The second thing to be aware of is the neutral safety switch is no longer the inexpensive, reliable switch that worked fine for many decades. It is a "range sensor". This one has five separate switches in it that turn on and off at different times. Those must agree with the short list of acceptable combinations. When any one of them does not go to the correct state, code P1899 will set.
Any one of these three codes will send the system into limp mode. Inspect the wiring harnesses first for signs of wires rubbed through, then for corrosion on connector terminals. The next step would be to use a scanner to view live data and see if either speed sensor is generating a signal. Also look at the Transmission Range Sensor to see how it is listed. I have a Chrysler DRB3 scanner for all of my vehicles. That shows the gear that is selected as interpreted by the Transmission Computer. You may be able to get an idea as to the cause of the problem by watching how it acts while moving the shift lever. If an incorrect gear reading only occurs when shifting between forward and reverse, with the engine running, for example, a good suspect is something related to a wiring harness that is flexing when the engine rocks. If the problem shows up when the engine is not running, an intermittent contact inside the range sensor becomes a better suspect. A problem in the range sensor could act up every time you shift to a certain gear, but it is usually the only suspect when the incorrect readings show up intermittently as you shift back and forth.
Wednesday, April 5th, 2017 AT 2:59 PM