NSS... Is it necessary?

Hey,

'88 XJ JC Laredo 4.0L Auto 4WD.

Been reading alot of NSS posts lately and what comes to mind is that what of the NSS; is it absolutely necessary?

It controls the ability to start only in neutral or park, right? And, it turns on the Back-up lights.

What about doing away with the NSS by figuring out which wires tell it that it's in N or P and then connecting them together so it thinks its in N or P all the time and wouldn't it then start in any position then?

Anyone's tried this please let us know which wires they connected.

Thx, Phil

Are you planning on making this a trail only rig or are you planning on driving it on the streets too?

The NSS is a SAFETY device (hence the word in the name). If you plan to run your jeep on the street, I would highly encourage you to keep the NSS.

As far as the connections, you can find a diagram of it in the FSM (you have already donwloaded this haven't you?). It will tell you which pins are connected for a given shifter position.

Are you planning on making this a trail only rig or are you planning on driving it on the streets too?

The NSS is a SAFETY device (hence the word in the name). If you plan to run your jeep on the street, I would highly encourage you to keep the NSS.

As far as the connections, you can find a diagram of it in the FSM (you have already donwloaded this haven't you?). It will tell you which pins are connected for a given shifter prosition.

Hey Saudade,

Thx 4 the reply. No, Street Machine only couldn't justify spending a lot of money to fix her up then bash it all to hell on the trail (tho it would be fun).

Since it is a Safety Device thereby preventing you from starting in gear. I'm the only one who uses the Jeep so no danger of that. lol

However, if I connect the wires to fool the NSS into thinking it's in N or P what about the Back-up Lights will they still function normally?

btw - Yes, I've DL the FSM but haven't perused it yet ;) And, I'm only attempting this so I won't get stuck anywhere if the NSS fails then the only other thing to think about failing is the CPS. Which is new.

Thx, Phil

If you completely eliminate the NSS, you'd have to rig up some other switch for the backup lights. If you're only worried about NSS failure, you can easily jumper the wires at the connector which is fairly easily accessed from the engine compartment. I carry several jumper wires with alligator clips and a few "pigtails" with various connectors (M/F) on them, just in case I need to bypass something.

The FSM will indicate which terminals are connected for various positions of the shifter. Make a copy or write them down and leave it in your glove box.

If you have a 4 speed tranny then you need to jumper the B and C wires together. By doing that it sends a signal to the ECU that makes it think it's always in park and can be started in any gear. And on the contrary by jumping those 2 wires together it will not disable the backup lights. I have done this on my 92 cherokee sport and also installed a push button start switch and the backup lights work without any problems.

If you have a 4 speed tranny then you need to jumper the B and C wires together. By doing that it sends a signal to the ECU that makes it think it's always in park and can be started in any gear. And on the contrary by jumping those 2 wires together it will not disable the backup lights. I have done this on my 92 cherokee sport and also installed a push button start switch and the backup lights work without any problems.

Hey Dave,

I have the AW4 Automatic. I think it's the "Selectrac".

1. Do you think on an Automatic jumpering the B and C wires will still be the same?

2. Also, do you think my Backup Lights will still work like yours after jumpering?

Thx, Phil

Just so all who are reading this thread will know I have the AW4 Aisin 4 speed automatic with the NSS that's like $200 to replace. I do currently have the wires jumpered about 2 in. back from the plug in connector and the Jeep will start in any gear from park to 1st and the reverse lights work without any problem. In theory the 3 speed NSS could be jumpered the same way but with different wiring, following is the wiring design for the 4 speed and 3 speed tranny's. On the 4 speed in park and neutral a "good NSS" has continuity between pins B and C, in reverse there is continuity between pins A and E, in drive there is no continuity between any of the pins, in 3 there is continuity between pins A and G, and in 1-2 there is continuity between pins A and H. On the 3 speed tranny's I haven't done it but it should be the same result as the 4 speed's but for them in park and neutral the center wire should be grounded to the tranny case or any good clean ground. If any one out there own's a 3 speed and tries it by grounding the center pin to a good clean ground point somewhere let us know if it has the same effect as mine as being able to be started in any gear and if the reverse lights still work. I keep mine wired like that but it didn't fix my original problem I had with the jeep so I'm still stumped on it for now. It's a 92 cherokee sport inline 4L HO and it won't start with the ignition key at all. I've replaced the ignition switch located on the lower end of the steering column, the starter relay, starter and solenoid, cleaned NSS top to bottom and checked all contacts and it's good, tried grounding the tan/yellow wire going to the starter relay on the underhood fuse block, tried grounding the same wire going to the ECU, even tried completely removing the NSS from the circuit and providing the same ground signal and still nothing. I was at a loss as to what was causing the problem so I ran two 12 gauge wires directly from the starter to a momentary push button inside the jeep and located it to the bottom panel part of the dash so right now all I have to do is put the key in and turn it on and then just press and hold the button for a couple secs. and it does the same thing as if you were putting a screwdriver across the starter. I also was having trouble in that once I got it started that way I would put it in gear and it would drive but when I went to stop it wouldn't go into park so I shut it off and tried all the gears and it would not go into park or 1-2. So to resolve that problem there's a little actuating rod on the upper part of the steering column that's about 3 in. long and provide the steering lock that prevents the vehicle from being put into gear without the key on. So right now my jeep can start with the push button and can also be put into any gear without the key even being in the ignition which is nice if you're working on it and have to move it a matter of a foot or two. I don't recommend doing all this to any jeep as I have mine as they are all safety measures put in place to prevent people from being hurt. But by doing those few things I have bypassed alot of problems that I have seen people have with ignition and shifting problem. If anyone else tries any of this out on they're jeep let us know what result you had especially if you try jumpering the wire on a 3 speed tranny.

It control the transmission computer (later models for sure). It will give a check engine light. They call it a PRNDL switch at the dealer shops. Those are the transmission positions.

Why don't you just take it apart and rebuild or replace it?

First if you bypass the NSS like I did IT WILL NOT make the check engine light come on. Second the guys in this thread are wanting to know how to bypass it completely as everyone knows where to get a new one and how expensive they are.

I think we might be talking about apples and oranges here.

What you are doing is jumping the Neutal Safety position in what is called the Transmission Range Sensor which besides the NSS funciton, sends signals to the Transmission Control Unit. See the 2000 XJ manual (which is downloadable) on P. 410 and you will see that signal T1, T2 and T3 are sent by that switch. I say that because I had to rebuild my Trans Range Sensor for engine light, backup light and neutral start issues. If you do rebuild it you will see the wear points in it, which is why I think bypass is not a long term cure all. If you rebuild it, it cost nothing except time.

I don't know anything about the 2000 model XJ but I do know what works on a 92 XJ with the 4 speed tranny and the NSS that everyone has a problem with. On it you don't rebuild it you just take it apart and clean it and regrease it and I already did that to mine and it still didn't work so I jumpered it to totally bypass it as I'm the only one who will be driving the Jeep. I put great detail in the second post on this thread which came from the Hayne's repair manual I had sitting in my lap, I also included in that same reply the different connections the switch makes for different gears on the 4 speed which is what everyone seems to have the problem with and what Digitruck was wanting to know if it could be bypassed and would it affect the backup lights. In answer to his question yes it can by jumpering B and C together and no it will not affect your reverse lights or cause the check engine light to come on on the earlier models like a few of us own. As for other models after 97 I don't know about them as I don't own a manual for them but hopefully Jeep recognized the problem they were having with the NSS for the old 4 speed tranny and fixed it for good.

The AW4 unit has been discontinued. I still have the last year made, the 2001. I guess if I keep the old XJs long enough, I might have to do like you.

Chrysler-Benz now uses a different transmission in the 4.0L Wrangler. Even that is being replaced for 2006 (or 07) with the 3.7L and powertrain.