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Old 05-22-13, 11:32 AM   #1
SliC300
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Default Neutral Safety Switch

Alright, so I have searched and the only thing I found was how to bypass when doing a 1jz swap. So I recently swapped my Sc300 auto tranny to a W58, and I am also swapping the auto ECU to a manual one. Would the bypass posted by Biggu work on a 2jz harness? or is his solution specifically for the 1jz? I remember seeing another post by RedPhoenix I think about how to overcome this lame switch when he converted his Sc400 to manual, but those picture won't load anymore for some reason, plus it was an Sc400, so there was no real option for him using a manual ECU.

I guess the Question is with the manual ECU installed, would Biggu's solution work? or do i not need it at all? or should I just jump the auto tranny plug (which i already did), or is there something more simple that can be done about that damn switch?

Note: I recall looking at my friends pedals, his Sc was manual stock, and seeing a switch connected to the pedal frame, i assume this switch is some sort of NSS, and I wonder if that switch is also under the auto Sc's...



It seems so simple, just jump two wires and done! problem is... which two wires...
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Old 05-22-13, 01:35 PM   #2
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The NSS depends on what body harness your car has in it, which is usually the one it came with.
So even if you use a manual ecu with a manual engine harness, your body wires that go to the NSS pin, the ignition switch, and starter are all still the auto body harness. If you look at the wiring diagram for the NSW there are 2 different ways its wired in the body harness for the sc300.

The manual one goes to one of the 2 switches on the clutch pedal, the one that gest pressed when its all the way at the floor, the other one is for cruise and that gets activated as soon as you move the pedal even a hair. 2 completely seperate switches. To bypass the NSW on a manual car, you simply remove the plug on the correct switch, and jump the 2 pins and that also means no more clutch needed to start the car at all, it will start in gear if its in gear.

for the auto, it goes through all the shifter stuff and I would think you still have to do all the stuff all the auto guys have to do even though you have a manual ecu, cause all the wiring is still the auto. remember there is only 1 pin for NSW and its in the same spot on all the ecu's its the wiring in the car thats different.

I have always wondered if one could bypass this just at the ecu, but I haven't experimented with that.
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Old 05-26-13, 03:20 PM   #3
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Great info!
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Old 05-26-13, 05:01 PM   #4
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I cannot help confirm anything for original automatic cars but I did this the other day in my original 5-speed by disconnecting that little two-wire connector that goes into your pedal assembly and using a couple of narrow jumpers from Radio Shack on it to complete the circuit.

At least on original manual cars it is that simple to do. It makes it simple to return to stock as well.

I've only heard of the need for this on cars with R154's and V160's with pull-type clutches however, especially high clamp load aftermarket ones. It is only helpful upon startup when oil pressure to the thrust bearing hasn't built up yet.
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Old 05-27-13, 01:03 PM   #5
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Yes Khan that is right for manual cars it is that simple, I have had a jumper in there ever since I changed out the stock clutch which didn't last 2 weeks after I went na-t so I got the extreme pressure plate (bad idea) and did the bypass (very good idea).
your crank does not need the extra wear on start up and heavier pressure plates add to the problem, with push and pull as I understood it you are just wearing different bearings as there are lots of thrust bearings, but it will still wear them down. If you can remember to not start it in gear it is beneficial, I don't leave it in gear my parking break works =) My 85 comes factory with no NSS it will just start right up.

Most SC are auto's though, and it can be much harder to get the car started than that, and I think the same or similar bypass needs to be performed to get a swap started in an originally auto car.

Last edited by Ali SC3; 05-27-13 at 01:13 PM.
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Old 05-29-13, 01:28 PM   #6
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Thanks for the input and especially the diagram Ali. I don't see why messing with the ecu pin for the NSS wouldn't work, I may have to try it at some point in time lol. But it seems to me that if you just jump the position plug for the auto harness it should crank, since that's all that is indicated in the schematic. Either way, I did already, and if it doesn't work, I'll use Biggu's method and hope for the best. I'll keep the thread posted
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Old 06-04-13, 04:09 PM   #7
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Alright, so to update people, jumping the two pins on the auto tranny plug, the one that i assume senses the position of the PRND lever, will indeed allow you to start the car. I actually started it today, and even after almost three years, it started on the first crank . So, if you do an auto to manual swap, all you have to do is jump the pins in the plug, as Biggu showed in the last picture of his thread.

Well, at least this worked for me lol
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Old 06-04-13, 05:26 PM   #8
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^^nice, it really does seem that would work from the diagram either jumping the pins for park or neutral as either looks like it would complete the circuit. If you still have the auto cluster in you should be able to see which position it is in.
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Old 05-15-14, 03:53 AM   #9
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Question!! I have that switch for the manual that goes on the clutch pedal (shown in the first pic) but my car is an original auto sc 300. So can i still use it to bypass the nss or connect it with the auto tranny plug?
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Old 05-15-14, 08:32 AM   #10
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You just wire your new switch on the clutch pedal to the NSS on the auto plug, that way when you push in the clutch you are in neutral to start, and when you let go it goes out of neutral. I think. honestly I have a stock manual car and I bypassed my switch so long ago I forgot there is even one. I wouldn't bother taking the time to install it but you can just wire it up to the NSS if want it.
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Old 05-15-14, 08:39 AM   #11
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Bypass Neutral Safety Switch....

Pin 23 of IK2 (White 25 pin) to Pin 6 of IJ1 (Grey 14 pin)

You need to do this or car will not start if you are using Auto ECU
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Old 05-15-14, 10:51 AM   #12
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exactly. some just jumper it and leave it like that, some connect it to a pedal switch or the parking brake. I would just jump it and call it a day.
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Old 05-15-14, 11:05 AM   #13
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Essentially by doing this bypass you make the ecu think it is always in neutral.....

Ali....Have you noticed a difference at all since you switched to a manual ECU?
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Old 05-15-14, 01:01 PM   #14
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Yeah its a bit more peppier and there is no hesitation the first time I push the throttle after starting.
since 5 speeds don't have trac and all the gte's do, if you have an auto ecu on a car without trac the first time you press the throttle it will go slowly as it figures out the sub tps isn't working, then it revs smoothly the next time you rev it all the way until the next start. I think you could solve this by just doing the ressitor fix for the sub tps, but I am lazy and figured I would eventually get the manual ecu. The manual ecu it revs smooth on the first press and feel great. not really a big deal but I am picky I guess.

also there is no feeling of the auto ecu pulling timing when it thinks it should shift when you are at lower speeds you can only really notice it, or when you want to downshift from cruising sometimes. IMO not having those 2 issues and the increased rev limiter it makes sense to just use the 6spd ecu on sc300's that are 5 spd, it really runs fantastic on my car, but to be fair the aristo ecu really did 95% of the job and apart for those 2 minor things drive the same pretty much.

I did feel like the supra has a tiny bit more pull in boost on the butt dyno, but that could just be the little more rev limiter or maybe it does have a slightly more agressive tune on it, its not really enough of a difference to say for sure. both are leagues above the stock n/a ecu, but this 6 speed ecu is permanently staying in now.. lol.
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Old 05-17-14, 11:17 AM   #15
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Thanks for the info Ali + Catman. The reason why i asked and wanted to wire it through the clutch pedal was i read somewhere on the forum that with the nss bypass there's a hesitation when you rev or something. Plus i wanted that safety (pun intended) just incase my wife ever ever ever had to start or try to move the once the conversion is done.
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