• Welcome to the new NAXJA Forum! If your password does not work, please use "Forgot your password?" link on the log-in page. Please feel free to reach out to [email protected] if we can provide any assistance.

How NOT to fix your XJ's Neutral Safety Switch (NSS)

B

brandonvalentine

NAXJA Forum User
Location
Nashville, TN
From the how-the-heck-am-I-going-to-get-home department comes this ninja move:

Let's say you're out somewhere and your notoriously finicky NSS has finally gone to Jeep heaven. No amount of jiggling the shifter or moving back and forth between Park and Neutral will get her started. You know, because you've been sitting there freezing your ass off trying for a good 30 minutes now. You know you should have replaced the thing last week but you just didn't have time. How do you get home or at least to a place where you can safely lift the Jeep and do the repair?

Look on the rear passenger side of the engine for the 8-wire harness coming from the neutral safety switch. There are two wires in this harness, pins B and C on the plug (two center pins opposite the clip that holds the harness together, look in a shop manual for a diagram, they are labeled on the plug in my Jeep), which control current to the starter relay. When the NSS is in park or neutral pins B and C are shorted and the circuit through the starter relay is grounded, allowing the starter to crank. What you need to do is ground this circuit yourself. Find yourself a paper clip, or in my case, a safety pin. Cut the head off of the safety pin and wedge it down the back of the engine side of the NSS harness plug between pins B and C, as far in as it will go. Voila, your Jeep will now start in any gear. DON'T START IT ANY OTHER GEAR THAN P or N!

Drive it home, and immediately order yourself a new NSS off of eBay where they're way cheaper than the dealer or auto parts store, and hurry up and get that safety pin out of your wiring harness!
 
brandonvalentine said:
From the how-the-heck-am-I-going-to-get-home department comes this ninja move:

Let's say you're out somewhere and your notoriously finicky NSS has finally gone to Jeep heaven. No amount of jiggling the shifter or moving back and forth between Park and Neutral will get her started. You know, because you've been sitting there freezing your ass off trying for a good 30 minutes now. You know you should have replaced the thing last week but you just didn't have time. How do you get home or at least to a place where you can safely lift the Jeep and do the repair?

Look on the rear passenger side of the engine for the 8-wire harness coming from the neutral safety switch. There are two wires in this harness, pins B and C on the plug (two center pins opposite the clip that holds the harness together, look in a shop manual for a diagram, they are labeled on the plug in my Jeep), which control current to the starter relay. When the NSS is in park or neutral pins B and C are shorted and the circuit through the starter relay is grounded, allowing the starter to crank. What you need to do is ground this circuit yourself. Find yourself a paper clip, or in my case, a safety pin. Cut the head off of the safety pin and wedge it down the back of the engine side of the NSS harness plug between pins B and C, as far in as it will go. Voila, your Jeep will now start in any gear. DON'T START IT ANY OTHER GEAR THAN P or N!

Drive it home, and immediately order yourself a new NSS off of eBay where they're way cheaper than the dealer or auto parts store, and hurry up and get that safety pin out of your wiring harness!
Click to expand...

Thx for the info... Some advise however .. they can be rebuilt very cheaply and easily. Instead of having to buy another one ... weither it be from ebay or the dealer.

http://www.go.jeep-xj.info/HowtoNSSrebuild.htm
 
brandonvalentine said:
Very true and very good advice. However, I've done that several times and at this point I think it's replacement time. The springs are pretty much shot.
Click to expand...

Once you replace it, can I have your old one? I'm working on a few ideas, and I need to collect some samples (some sacrificial, some not...)
 
5-90 said:
Once you replace it, can I have your old one? I'm working on a few ideas, and I need to collect some samples (some sacrificial, some not...)
Click to expand...

Well, I'll probably keep it around as a spare since these things are so expensive, but if you can convince me I'd be donating to a good cause, I might change my mind. What have you got up your sleeve? ;-)
 
brandonvalentine said:
Well, I'll probably keep it around as a spare since these things are so expensive, but if you can convince me I'd be donating to a good cause, I might change my mind. What have you got up your sleeve? ;-)
Click to expand...

Mainly, working on some replacement parts to allow you to rebuild the thing, instead of just cleaning it. I may come up with some other ideas while I'm working on that, but figuring out specs and dims on contacts and springs are where I'm starting, and seeing if a suitable replacement for the "collet fingers" around the shift shaft are where I'm starting.

Considering what the thing can cost new, I figure if I can offer "rebuild kits" that allow you to replace contacts and such (for considerably less!) is a step in the right direction. From what I've seen, the contact strips in the shell don't seem to wear down, so the replaceable contacts would be in the wiper arm.

That's essentially it at the moment - I just need to collect examples spanning pretty much every year (or group of years - RENIX, OBD-I, 1996, OBD-II...) to see what variations there are. What year is yours?
 
brandonvalentine said:
Once I get it replaced and spend a few weeks driving around with the new part on the truck so I trust it I'll get back to you.
Click to expand...

Cool. I can send you a postpaid box if you like (no reason to make you pay for shipping the thing, and it's deductible for me anyhow...)
 
5-90 said:
That's essentially it at the moment - I just need to collect examples spanning pretty much every year (or group of years - RENIX, OBD-I, 1996, OBD-II...) to see what variations there are
Click to expand...
Just how many varients are there Jon?

I have dibs on a '96 tranny/TC as stand-by for my '90. Are these parts going to swap out?
 
Hypoid said:
Just how many varients are there Jon?

I have dibs on a '96 tranny/TC as stand-by for my '90. Are these parts going to swap out?
Click to expand...

I don't know - that's why I'm collecting them.

You should have no trouble swapping the transmission. You can probably swap the NSS (I haven't checked part numbers yet, either,) but I won't swear to anything at the moment. However, I don't think there were any internal mechanical or electronic changes over the life of the box, so that shouldn't be any trouble for you (I've taken them apart from 1987 to 1995 - but the later ones I'd gotten as cores and such didn't have NSS's on them.)
 
What are the chances of a NSS from a 91 TOY 4 Runner working in my 88 Cherokee. The trans is a 4 speed but the engine is a v-6 in the TOY.
They look the same physically but I haven't looked at the connector diffrence if any. (lazy me)

I tried to run the part numbers from the online parts places and i found them to be diffrent.
If someone could cross reference it it would help.
 
B.RAIDER said:
What are the chances of a NSS from a 91 TOY 4 Runner working in my 88 Cherokee. The trans is a 4 speed but the engine is a v-6 in the TOY.
They look the same physically but I haven't looked at the connector diffrence if any. (lazy me)

I tried to run the part numbers from the online parts places and i found them to be diffrent.
If someone could cross reference it it would help.
Click to expand...

Fair to middlin', I'd say. The RENIX AW4 NSS connector is a 4x2 Deustch, and I think Toyota used a lot of Deustch connectors. I remember the connector because I found it odd - RENIX uses mainly Delphi Weatherpack connectors, so it stands out...
 
5-90 said:
Fair to middlin', I'd say. The RENIX AW4 NSS connector is a 4x2 Deustch, and I think Toyota used a lot of Deustch connectors. I remember the connector because I found it odd - RENIX uses mainly Delphi Weatherpack connectors, so it stands out...
Click to expand...
Swap the connectors perhaps????
The reason I ask is because I have access to the parts from the 4 runner and I do plan on doing the NSS fix.....just woudering if it could possibly work.
 
You could probably reterminate, if you have to. Splice it into the connector removed from your OEM NSS (which I could probably still use, if you don't hack up the body.)

Do you need a truth table for the thing? If you have an FSM, you have one - if you have a Chilton's, you might (I don't recall.) If you have neither, I have my 1990 FSM handy - and the truth table for the 1990 is the same as the 1988, so I could scan it and email it to you.
 
5-90 said:
Do you need a truth table for the thing?
Click to expand...
Forgive my ignorance....but what are you refering to here? :huh: :)
As mentioned in next post...below (citizenatlarge) .... I'm thinking of a wireing diagram ...perhaps???
 
Last edited:
Me too! lolz.. but, i imagine that he may be referring to the details about each when working correctly.. Such as, voltages etc.. on each contact?? And interactions/effects maybe?

I have NO idea how deep a Truth Table might go! TTFN! lolz
 
B.RAIDER said:
Forgive my ignorance....but what are you refering to here? :huh: :)
Click to expand...

Sorry. A "truth table" is used to cleanly display the anticipated outputs from a series of logical decisions or a multi-state switch.

Let's say, for simplicity, we have a "Logical NOT" circuit (reverses output.) The truth table for that would be:

INPUT OUTPUT
ON OFF
OFF ON

Next step - a "two-input AND" (for the output to be ON, both inputs must be ON):

IN1 IN2 OUTPUT
OFF OFF OFF
ON OFF OFF
OFF ON OFF
ON ON ON

A "truth table" can also be done backwards - where a single "input" can drive several "outputs." Since you talked me into it (and it's the only example I can think of...) I dug out my 1990 FSM and looked up the AW4 switch Truth Table ("input" is gear selector position, "outputs" are the various terminals on the connector, A thru H. "X" means that circuit has continuity with the other "X"):

IN B C A E G H
P X X (B and C)
R X X (A and E)
N X X (B and C)
D (No Continuity)
3 X X (A and G)
1/2 X X (A and H)

Damned formatting blew up when I hit "commit." I'll do a nice one later for the WiP Tech Archive anyhow, once I have a chance...

So you can now see that, if you tie B and C together on the vehicle side of the harness, the system will think that the selector is in Park or Neutral, and will allow the starter motor relay to operate (this is how you bypass the NSS.) Continuity with anything paired with terminal "A" means that the vehicle is in a range where it can move under power, but not in Drive. That way, the TCU "knows" that certain gears are not available. The default signal is "No Continuity" (Drive) - meaning that all forward gears are available.

Essentially, a "truth table" is a simple way of organising a potentially large amount of information (like for complex logical selection circuits.) However, a truth table can be used in any situation where there is some variety of decision-making being made by a switching array - like a truth table for electronic solenoid switching, or for switching a hydraulic control system with various valves. It provides a simple and concise format for presenting useful information - usually for troubleshooting, and each line may be read as "If <input> then <outputs>. Like "If gear selector is in Park, then continuity exists between B and C." But with far less ink.
 
Last edited:
5-90 said:
Sorry. A "truth table" is used to cleanly display the anticipated outputs from a series of logical decisions or a multi-state switch.

Let's say, for simplicity, we have a "Logical NOT" circuit (reverses output.) The truth table for that would be:

INPUT OUTPUT
ON OFF
OFF ON

Next step - a "two-input AND" (for the output to be ON, both inputs must be ON):

IN1 IN2 OUTPUT
OFF OFF OFF
ON OFF OFF
OFF ON OFF
ON ON ON

A "truth table" can also be done backwards - where a single "input" can drive several "outputs." Since you talked me into it (and it's the only example I can think of...) I dug out my 1990 FSM and looked up the AW4 switch Truth Table ("input" is gear selector position, "outputs" are the various terminals on the connector, A thru H. "X" means that circuit has continuity with the other "X"):

IN B C A E G H
P X X
R X X
N X X
D (No Continuity)
3 X X
1/2 X X

So you can now see that, if you tie B and C together on the vehicle side of the harness, the system will think that the selector is in Park or Neutral, and will allow the starter motor relay to operate (this is how you bypass the NSS.) Continuity with anything paired with terminal "A" means that the vehicle is in a range where it can move under power, but not in Drive. That way, the TCU "knows" that certain gears are not available. The default signal is "No Continuity" (Drive) - meaning that all forward gears are available.

Essentially, a "truth table" is a simple way of organising a potentially large amount of information (like for complex logical selection circuits.) However, a truth table can be used in any situation where there is some variety of decision-making being made by a switching array - like a truth table for electronic solenoid switching, or for switching a hydraulic control system with various valves. It provides a simple and concise format for presenting useful information - usually for troubleshooting, and each line may be read as "If <input> then <outputs>. Like "If gear selector is in Park, then continuity exists between B and C." But with far less ink.
Click to expand...
I find this information helpful...THANKS...I'm gonna save it for future use.
 
You must log in or register to reply here.

Similar threads

D
1996 4.0 No Crank, Starter Works When Jumped
2
Replies
20
Views
303
DirtySouthXJ
D
M
92 XJ ECU connector
Replies
5
Views
140
Rob Mayercik
R
C
Cranking Time
Replies
6
Views
86
CBJeeper
C
Z
1990 renix electrical issues
Replies
3
Views
91
cruiser54
C
W
‘99 4.0 - DIY ignition kill switch
Replies
6
Views
1K
techno1154
techno1154
Back
Top