It sounds to me like the 12V signal going into your TCU to make it function isn't getting there. I actually have this wire running through a toggle switch so I can turn it off and lock my auto tranny in 1st gear for rock crawling. Your tranny is acting just like mine does when I have this power to the TCU switched off. Pin C15 on your TCU plug should have 12 volts going to it whenever the ignition is turned on. I bet that power is not getting there in your Jeep. If that power is not getting to your tranny it acts pretty much like a manual tranny. Only it goes directly to whatever gear you have selected with the shifter. I.E....how you say it will go to Reverse or Drive only. I bet if you put it in 1, it will go to first and if you put the shifter to 3 it will also go to 3rd gear. Check for the 12V signal at pin C15 on your TCU plug. Make sure you have your igntion switched on.

 

u can delete this thread i figured it out to be a faulty tps sensor

 

I was just going to say check your TPS had mine drove me crazy and a customers doing the same thing, but both would shift after the vehicle got hot.

 

I gave my NSS a cleaning because I had problems starting it and also because the reverse lights didnt work.

Now the reverse lights work and all is ok (kind-of, for now...)

A concern I have is that I cant start the engine in NEUTRAL. Surely it should be able to start in 'N' , right?

 

I drove my XJ for a couple of years with the TCU unplugged...had to shift manually which means 1st-3rd-OD.

If the trans shifts fine with the TCU unplugged, there isn't anything wrong with the tranny. It is the electronics--either the TCU or one of the billion or so sensors feeding info to the TCU.

 

That is a good lesson for all of us so the thread stays. Thanks for sharing your final fix solution.

 

no problem..