Howling_wolf

ok I have a 93 Jeep Cherokee 4.0 aw4 transmission 4x4
I have been working on this for awhile so hear it is its stuck in limp mode so it only shifts in 1-2 R gear no D so Iv been wire tracing for a long time Iv replaced the tps iv been driving it with the tcu unplugged I just now got schematics for the tcu and pcm and traced it down I have no power to the D wire when in Drive with key on engine off and now I have no power to the 1-2 gear wire the wires go to the Shift Position Sensing Unit and I have power going to the dark blue/white wire so I don’t realy know so does that mean my shift position sensing unit is bad and how would I test it

sean882

When you say the Shift Position Sensing Unit, I believe you are referring to what is called the Neutral Safety Switch (NSS) around this forum, and the fsm, even though it isn't a standard nss. It is also responsible for reverse lights, among other things. Heres a Link with some info about it, as well as how to clean it out. I'm not sure how you would go about testing it, maybe someone else on here knows?

Also, I'm not sure of what you mean by the "D" wire in the schematics. Which schematics are you looking at? It would make it easier to help if we were all looking at the same diagram/same labels, if you could post it.

moparboy

Having a similar issue on my '98. Was wondering how I go about fixing this.

I may just go ahead and buy the Chilton's and figure out if it can be cleaned.

syncview

first of all, disconnect the -ve terminal of your battery for like 20 mins and then reconnect. Start the engine up and keep it running for about 3 to 5 mins.. some revving and shut it down. Start up again, disconnect the NSS Switch connector which is near to the valve cover.. your Jeep should keep running. Now try driving in D and see what happens, oh and plug the TCU in before doing all that :P The NSS doesn't ANY signal when the shifter is in D position, so it should drive fine if your transmission and TCU are working fine.

And all that may sound stupid, but believe me.

Search for 'engine is revving fine', a thread made by me.. and have a look. Good luck and do get back to us.

fantic238

Hehe, sincview has become an expert about this issue...

syncview

Thankful to you Fantic :P

Howling_wolf

Well I put a new NSS in and got the power back to 1-2 gear but I did everything SYNCVIEW said to do and still will not shift out of 1-2 gear while in Drive so its like its stuck in limp mode its got 12vdc on C15 on the TCU plug but when I unplug it and shift it manually it works fine so if it's the TCU how can I test it to find out