Brake light switch and neutral safety switch problems

jtown125 · 04-28-2010, 06:32 PM

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)

ANY SUGGESTIONS would be greatly appreciated!!!! Thanks!

Supra_Freak_7m · 04-28-2010, 06:41 PM

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.

jtown125 · 04-28-2010, 06:58 PM

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!!!!

Supra_Freak_7m · 04-28-2010, 07:09 PM

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

try those and see if that works

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

jtown125 · 04-29-2010, 01:32 AM

Well... I fixed the brake light switch...YAY PARTS CARS!!!!

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???

CanadianBak'inSupra · 04-29-2010, 02:29 AM

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

cre · 04-29-2010, 02:47 AM

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.

CanadianBak'inSupra · 04-29-2010, 02:56 AM

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

Supra_Freak_7m · 04-29-2010, 04:12 AM

Quote:

Originally Posted by jtown125

. 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???

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

jtown125 · 04-29-2010, 04:08 PM

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!!!!

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.

04-28-2010, 06:32 PM	#1
jtown125 Intake Join Date: Apr 2010 Location: Tennessee Posts: 40	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) ANY SUGGESTIONS would be greatly appreciated!!!! Thanks!

04-28-2010, 06:41 PM	#2
Supra_Freak_7m Intake Join Date: Apr 2010 Location: Montana Posts: 40	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. __________________ 1987 Toyota Supra 7MGTE AUTO 1987 Toyota Supra 7MGE MANUAL 1990 Toyota Supra 7MGTE AUTO-> MANUAL

04-28-2010, 07:09 PM	#4
Supra_Freak_7m Intake Join Date: Apr 2010 Location: Montana Posts: 40	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 try those and see if that works NOTE: there are instruction on how to do a diagnostic in the FAQ __________________ 1987 Toyota Supra 7MGTE AUTO 1987 Toyota Supra 7MGE MANUAL 1990 Toyota Supra 7MGTE AUTO-> MANUAL

04-29-2010, 02:29 AM	#6
CanadianBak'inSupra Official hall monitor / search nazi - NO SOUP FOR YOU! Join Date: Oct 2009 Location: Canada, BC Posts: 837	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 __________________ 1984 supra - 1uzfe - w58 - 4.10 - 1 piece aluminum shaft.

04-29-2010, 02:47 AM	#7
cre Toyota Racing Development Join Date: Apr 2007 Posts: 5,038	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. __________________ If something breaks or you need to contact a member of the administration please post HERE. Unless it's a private or administration matter please post it on the forum. It benefits no one else if car related questions aren't posted for future users and takes away from the time I'm able to spend helping on the rest of the forum. If you're so inclined I'm always more than happy to accept tips via PayPal. Tip Jar ---> Last edited by cre; 04-29-2010 at 02:52 AM.

04-28-2010, 06:58 PM	#3
jtown125 Intake Join Date: Apr 2010 Location: Tennessee Posts: 40	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!!!!

04-29-2010, 01:32 AM	#5
jtown125 Intake Join Date: Apr 2010 Location: Tennessee Posts: 40	Well... I fixed the brake light switch...YAY PARTS CARS!!!! 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???

04-29-2010, 02:56 AM	#8
CanadianBak'inSupra Official hall monitor / search nazi - NO SOUP FOR YOU! Join Date: Oct 2009 Location: Canada, BC Posts: 837	thanks for the good reading links (i know there not for me) but thanks anyways!!! __________________ 1984 supra - 1uzfe - w58 - 4.10 - 1 piece aluminum shaft.

04-29-2010, 04:08 PM	#10
jtown125 Intake Join Date: Apr 2010 Location: Tennessee Posts: 40	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!!!! 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.

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