Brake light switch and neutral safety switch problems
 

Well, I have a problem. Brake lights are staying on, on a 89 supra. I'm going to assume its the brake switch, cause that is the only thing that could cause them to stay on in the first place right????... ALSO, the car will automatically shut off if I put the car in neutral after 4th gear and also dropping down from 5th gear while going to a stop. (and sometimes when i'm just going fast and shifting harder) :roflwtf: ANY SUGGESTIONS would be greatly appreciated!!!! Thanks!

Sounds to me like you need a new neutral saftey switch and spray your brake light switch with some CRC QD Electrical cleaner( love that stuff) and make sure its not sticking.

Neutral Safety Switches are only on automatic transmissions though Right??? And i have a stick shift.... SO.... what else could cause it to die when i put it in neutral???? I don't think that there is any wires that could get pinched in the situation... I don't know if there is a kill wire or something??? I also think that it could be a short somewhere or a ground not completely grounded, noticing that it is an occasional problem. SCREW ELECTRICAL PROBLEMS!!!!

Oh, I thought you had an auto, i saw when you said fifth gear too i just thought it was a typo. In that case i have no idea what would cause the car to die between shifts. i think the first thing to do is make sure you dont have a diagnostic code stored in the computer indicating possibly a bad sensor (MAFS, TPS).

Check your connecter on your MAFS and make sure it is not loose

Also, check your negative battery cable, make sure it is tight and clean at both ends. The cable should be grounded to the block on the driver side pretty much directly above the engine crossmember. If you have to remove the bolt that holds it on, dont worry it is a dry hole, neither oil nor coolant will come spewing out of it:x:

try those and see if that works

NOTE: there are instruction on how to do a diagnostic in the FAQ

Well... I fixed the brake light switch...YAY PARTS CARS!!!! :wavey: I took it for a drive after i put the new switch on... and it shut off every time i was in fourth gear and threw it into neutral. I don't think it is a sensor, because the check engine light would come on right? SO, I'm not sure what else will do it besides a short or ground wire still???

my samurai did the same thing before i blew the engine...
would always die in between gears, i change the fuel filters and i cant remember if that fixed it or somthin else...
either way filter is like 8 bucks and mindless probly not a bad idea

No Supra ever came equipped from the factory with a MAF. ;) I don't feel like going over it again so soon, so read here for the details:
http://www.toyota-supra.info/forums/82082-post15.html



Now that we know the difference it'd be a good start if we knew if the OP was running a VAFM (7M-GE) or a KVAFM (7M-GTE). The VAFM is fairly robust but it is a wear component. If the internal resistance medium is worn down excessively it will give the ECU air flow information which isn't accurate and may cause the engine to due when the intake drops sharply.

If it is a turbo MKIII then it's running a KVAFM which while not a wear component it is very delicate. Do NOT ever try to clean one with ANY liquid solution... compressed air, tops. MAF safe cleaner is just that... FOR MAFS! Now, if this is a GTE, you didn't try to clean the AFM, right? Haven't dropped it either I hope. Diagnostic info for both types are linked to below. There are more tests that can be done, but that's more than you usually need to worry about.

Another common part is the TPS (Throttle Position Sensor). It too is a wear component and it can be tested for flat spots and wear. Search Google for information on testing potentiometers for flat spots and I'm sure you'll find some details on the how to side.

The TPS also has a switch inside which tells the ECU that the throttle has completely closed so that if other certain criteria are met it will modulate the ISCV (Idle Speed Control Valve) properly in order to maintain the preset idle RPM.

A clogged ISCV will also contribute to these issues and it doesn't hurt to pull off the ISCV periodically and clean out any oil or greasy buildup.

Lastly.... vacuum leaks... check for intake and vacuum leaks.

TPS calibration:
http://www.cygnusx1.net/Supra/Librar...ction=FI&P=100

ISCV information:
http://www.cygnusx1.net/Supra/Librar...ction=FI&P=106

AFM information:
http://www.cygnusx1.net/Supra/Librar...ection=FI&P=94 (GTE follows GE)

As for the brake lights... test the switch under the dash that the pedal's arm comes in contact with... there's only one.



OP, post the specifics of your vehicle when you ask for help.... better yet, put them in your sig and profile. :frown:

thanks for the good reading links
(i know there not for me) but thanks anyways!!!

Keep in mind, only a few of the codes actually make the CEL stay on. So do it anyway :) you might just learn something new about your car

By the way its an 89 mkiii turbo supra. And let me go ahead and say it IS NOT DYING!!!! There is no struggle or what not. IT SHUTS OFF. I don't see a vacuum leak causing that, if a vacuum was leaking it would make it run like shit at all rpm's. AND believe me... IT RUNS GREAT!!!! :wavey: I'm down to it being an electrical connection of some sort, I don't know where it is at, and I don't know how to pinpoint it either. I know the second i put it in neutral FROM 4Th gear it shuts down, especially if i move the shifter side to side. But it starts right back up and i can put it back in fourth gear and it will never show any problems while in gear. It only shuts off after 4th gear to neutral. I don't think this is just a practical thing that can be known about because im sure that there are many things that could cause it. When i wiggle the shifter in neutral and it shuts down faster, that makes me think i'm making a connection or wire do something its not supposed to. I don't know if there is a ground wire on the shifter, or that goes down to the top of the transmission. And i don't have an obdI reader right now, so getting the code isn't going to be possible. And i don't even think it is throwing a code cause everything shuts down, nothing responds.

if you don't want advice. you're wrong about vacuum less affecting every range of output and there are no wires running to the shifter. After market BOSs can also cause what you're experiencing.

details on how to check diagnostic codes is posted in the FAQ, sorry, thought i mentioned that.

good luck with it. see ya.

(CRE)......... I'm not trying to be mean or what not. I joined the forum list to have someone help me out. Your suggestions make no sense to me. I'm not someone who doesn't know anything about cars. I have been working on cars all my life. Vacuum leaks will cause a lot of things to go wrong. But if it was a vacuum leak it would struggle to die, same as a throttle position sensor and everything to that extent.

And neutral is neutral no matter what, a vacuum leak would affect it when it is sitting at idle just the same as it would be while putting it in neutral while driving down the road, your still running the same rpm's. I don't have a reader I said that. I don't know what bos stands for. I do know that the only thing that isn't stock is the cd player. Which could possibly have something to do with it if it wasn't wire up right...anything is possible.

Explain to me how a vacuum leak would cause it to shut off only after shifting up from 4th gear to neutral? A throttle sensor usually makes the rpm's go wacko whenever it is going bad. Thats why a sensor doesn't make sense to me...even though I can't check it in the first place... I could on the other hand, just go undo the neg. cable and reset the ecu. If it is a sensor the computer will erase it till it happens again.

These are the things that make most sense to me: A short in a wire, a bad ground, maybe even the clutch pedal sensor? (i would think it would mess up other than 4th to neutral though),

I drove it all day today. It died everytime after 4th to neutral. After 20 minutes of driving. I turned the car off, let it sit for about 15 minutes. And went off driving again. I tried to avoid 4th to neutral. But its a habit. The little time i did have it in neutral was shifting back down into second...and i drove for about an hour, and it didn't shut down once.

I don't like to waste time and money, i don't have money. And i need it to be fixed. But suggestions that don't make sense to me I can't see myself pursuing without a good explanation of how it would cause it to affect it in that way.

The only thing that made sense to me of your earlier post is the sharp drop in rpm's affecting the intake.

But y would it not die after pushing the turbo hard and letting off?
Like how you would break a motor in.
Going from +6 to 0 is a sharp drop to the intake,
unless it bypasses it some how. But turbo burns everything
over again, so I don't see how that is possible.

On the flip side of that with the intake pushing back?
Wouldn't a big amount of back pressure do the same thing?
3,000 to idle with to much back pressure...
i see that making it shut off...
the computer sees that there is to much pressure and
shuts it down.

On most of the new cars there is an Automatic SHUT DOWN Relay and switch....
But i don't think that the supra has one.

At the same time...Y only 4th to neutral?
The rpm's are still as high and the pressure will be still as much
shifting from 2nd back to neutral...but it hasn't shut off once like that.

What does the higher gear have to do with it?
If anything?

Alright, a little bit of clarification:

I believe cre meant to type "BOV" and not "BOS", referring to an aftermarket Blow Off Valve.

Checking codes on MKIII Supras does not require the use of a code reader, just a jumper wire or a paperclip. As stated above, details on how to check codes are here in the FAQ. Once again, keep in mind that just because the CEL is not on it doesn't mean that there are no error codes stored.


When you do the 4-N and 5-N shift, will it still die if you accelerate at partial throttle without boosting? Does it do it under half load? Full load?
Also, does it cut out regardless of what engine RPM's you shift at (lo vs hi)?

Oh, one other thing....

You're saying it's shutting off. Is just the engine shutting off, or does all electronics shut off?

give me a second....

Alright...

It does have a BOV. And it wasn't doing was it was supposed to do...how would it cause the car to shut off immediately?

I don't think that the rpm's have anything to do with the car shutting off. I could be wrong.

I took it out again after the last post and it died stopping from 3rd-N too....

but it has yet to shut down from 1-N or 2nd-N. And im always shifting anywhere from 2500 to 3500 rpm's.

Of course when since the gears are high in it i usually just leave it in 4th when going 40 mph. running 2500 or a little higher and then putting it neutral.

With the engine only having 3,000 miles on the rebuilt motor all of these things that people are saying aren't making any sense to me. They are the original parts though, so wear is def possible.

It hasn't died from full boost and quick let off of gas... BOV still does what it is supposed to do...from what I can hear.

I don't know if back pressure has anything to do with it...but the down pipe has 2 pipes and one is cut off. Which would cause a lot of backpressure.

It "dies", it just does it without any hesitation. my def of dying is chug chug chug chug....die....

All the warning lights will come on and i just put it back in gear and remove the clutch...

And i don't know about the electronic things...i would assume they stay on...the cd player don't work half the time so it usually stays off.

Okay, I'm starting to suspect the BOV.

Stock turbo supras came with a bypass valve instead of a blow off valve. Biggest difference between the two is that the bypass valve will redirect excess boost pressure back into the intake pipe between the AFM and the turbo, meaning all of the air stays in the intake system and is accounted for by the AFM. Blow off valves vent the excess pressure to atmosphere. Our computers are programmed to "expect" that air to stay in the intake system, so if it is vented to atmosphere the engine will briefly run rich after shifting (which can cause it to chug and die) because it anticipates more air in the intake than what is actually there.

Basically, as far as the computer is concerned, each time you shift your BOV creates a giant boost leak. The only reason I can think it does it in the higher gears is because it takes longer for the RPMs to get there, allowing you to build more boost pressure thus loose more air/pressure when you shift.

I suspect that since the warning lights come on, it's just your engine cutting out and not the entire car. This also makes me think it's not as likely to be a bad ground or a short

One thing i do know...IT DOES RUN RICH!!! lol

So, lets go ahead and say its the blow off valve. Y would it not die after boosting in a single gear?

And to fix it?

Well, the only thing I can think of is that the ecu has time to realize what happened and fix the fuel curve as the engine revvs down.

I was reading an earlier post of yours and you said that it doesn't die off after full boost, so I'm assuming during these times you reach a higher rpm which could help support my above statement.

Fixing the problem, AFAIK, would require either tuning in some way (piggyback ecu or something along those lines) or replacing the aftermarket BOV with a factory or an aftermarket bypass valve (they do make them). You usually don't get the same sound, but they provide better performance over an OEM one. If your donor car is a turbo and has the required parts, swap them in and go for a drive. If it still happens then that's not the problem, but I really think that will fix your problem.

FYI, when I had my 7MGTE I put an aftermarket high-flow cone filter and a AFM adapter on mine and it made the turbo spool and OEM BPV much more audible

I don't know how it can do it so fast though?? It is almost instintaniously.

Is there a way to reset the computer and maybe it will fix it in itself?

Since the BOV has been on for a while...y now?

I drove it home 600 miles from mississippi and not one problem.

And what was the cone shaped thing you were talking about?
how does that set up work?

BTW: The BOV is welded on to the intake.

Resetting the computer is easy enough, just remove the 15 Amp EFI fuse from the fuse box under the hood. It's supposed to only take about 30 seconds to reset, but I always leave mine out for a few minutes.

I'm not sure how it could be reacting so quickly, but I do know that different supras react differently to aftermarket BOV's. Some will run just fine, some will not let you shift at all without it dying.

Wish I had more answers for you as far as why it's happening now

Since your bov is welded on, you'd have to replace the pipe if you changed the valve out. OEM pipes are plastic lol

Oh, and the cone air filter.... Basically it was a universal 3 inch air filter (like a K&N cone-shaped air filter). You remove the factory air box from the AFM and in it's place you can install an adapter that bolts up to the AFM on one side and allows you to clamp on an aftermarket air filter on the other side. As long as you use a decent quality air filter, you can safely allow the engine to quickly draw larger volumes of air into the intake, creating more power and better throttle response

well, I don't really want to change the whole thing, I'll go reset the ecu tomorrow when i wake up see what that does.

And i think the set up your talking about it already on there. It is a very popular aftermarket part cause a lot of the supra's i have seen are set up that way if what i think you saying is what im thinking of....lol

thanks for your help...ill post back tomorrow and let you know what happened.

Check for and post codes FIRST.... then reset all you want. FYI, there's nothing but minor trim data recorded in the ECU, unless there's another significant problem elsewhere resetting it shouldn't make a noticeable difference.


I'm thinking it may be a bad IDL switch. (codes 51)

Reset the ecu yesterday, Drove it all day, and had no problems out of it. I even shifted the car into neutral after all kill gears, 3rd, 4th, and 5th, all with no problems.

I do expect it to the problem to come back, hopefully not in the close future.

And if it does, I will check the codes.

I think my car just has a mind of its own...lol

Thanks for everyone's help.

It'll have been one hell of a glitch, but kind of cool in a weird way. Hopefully that is all you see of the matter. Check your codes again soon regardless of whether it starts driving like absolute ass: There may be more than one problem causing all of this and resolving them will help prevent the symptoms from adding up to the point of seriously affecting the car's driveability.... I don't know what the hell you've got against checking them anyway, it's easy.