Trying to track down wiring for the TCC connector on my 86 s-10 blazer 2.8 2wd

ddog800 · 10-28-2009, 11:35 AM

Hey guys, haven't had much luck anywhere else, maybe someone here knows or can look since this forum is more specific to my engine type/etc... I just had my tranny replaced with a rebuilt one on my 86 s-10 blazer 2.8 2wd, but when they were swapping it out they realized that all of the TCC wiring is missing. The old transmission had the connector hooked up with 2 wires going nowhere (were cut about 6 inches up). They were unable to find the original wiring at all coming from the harness. I'm assuming the old one was rigged up with a lockup kit or something, but the one I replaced it with isn't.

I've been able to track down in schematics where the wiring is supposed to be coming from and the wire colors, but I'm having trouble tracking where they actually are under the hood. The schematics say there is a purple wire coming from the brake switch to supply 12V to the TCC, and then a tan/blk wire coming from the ECM (pin A7) which is the computer controlled ground. Unfortunately there is no purple wire coming from the brake switch, just orange/blk, white, grey, grey/wht (in 2 separate 2-pin connectors), so I'm assuming that it turns purple somewhere else. I haven't even tracked the ECM-controlled ground out of the firewall yet, though I have been able to spot it in the larger connector going into the ECM. I suppose I could try to rerun them from scratch, but that's a last resort as I'm certain the original wiring is in there somewhere. It would be EXTREMELY helpful if someone could take a look at the wiring and connector on a similar model truck as mine and just see where it leads and let me know so I can find the most likely place they would have cut it off at. Even if I knew if the wiring went toward the drivers side or passenger side would help.

At this point I'm only driving in short spurts to and from work as I don't want to damage my new tranny because the TCC isn't being properly regulated. Thanks for any help you can provide!

The_Raven · 10-28-2009, 09:54 PM

Don't worry too much about driving the truck. All you will lose is some gas milage.

TCC is simply an "on" or "off" device, and will only lock (turn "on") at highway speeds.

Does your truck have cruise control? I believe the grey and grey/wht wires are for the cruise.

Look for a second switch at the brake pedal, IIRC the connector will have a pink and the purple wire you need.

ddog800 · 10-29-2009, 09:14 AM

hmm, Ok, the main reason I was worried was that I was told that if I cruised at highway speeds for more than 15 or 20 minutes without the TCC being able to turn on, it would overhead my transmission and burn it up. If it's just gas mileage, I can deal with that

My truck may have at one time had cruise, but it certainly has never worked for me. The brake switch does appear to have 2 plugs going to it. One has the grey wires, the other has 2 orange/blk wires and 1 white wire. Did you mean this other plug, or another switch altogether?

The_Raven · 10-29-2009, 02:20 PM

It's true the tranny could get warmer than it would with the TCC locked, but definatly won't burn it up.

In a different vehicle, it was FWD, but had a TCC that worked on the same principle (also a GM), I had the TCC disconnected for years and did plenty of highway driving.

If the truck didn't have cruise than the grey wires might be for the TCC control.

One will have 12V ignition and the other will have 12V when the brake pedal is released, but not when pressed. This unlocks the TCC when the brakes are applied.

ddog800 · 10-29-2009, 03:34 PM

Ok, I went outside during lunch hour with a multimeter and did some digging. I was actually able to find a plug with a pink and purple wire, but it didn't have anything to do with the brake switch. It was connected to another set of wires just above the brake pedal switch. I did find 12V on the purple wire with the ignition on, but it didn't change whether I had the brake depressed or not.

So, I went back to the brake pedal switch and put my meter on the white wire on one of the plugs. With the ignition on I found that I was getting nothing when the brake is not pressed, and when I applied the brake I got 12V. This sounds like the reverse of how you described that I would need it to be, so perhaps this isn't the one I need. I imagine this must be the one that powers the brake lights since it's providing 12V when the pedal is applied?

I didn't have time to check the gray wires, will do that when I get off this afternoon, and I'll recheck the other ones for good measure (was kind of in a rush).

Thanks very much for the help.

The_Raven · 10-29-2009, 06:53 PM

Yes, the Orange(/black) and white wires are for your brake lights.

The TCC switch could be a seperate switch, though it is usually built into the same switch that controls the brake lights.

ddog800 · 10-29-2009, 10:46 PM

Yep, and according to every related diagram I could find on alldata that's exactly where it should be coming from. Unfortunately I didn't get a chance to check it before it got dark, so looks like tomorrow's another day (if it's not pouring rain like I think it will be).

ddog800 · 10-31-2009, 02:21 PM

Update:

OK, I just spent a little while testing all of these wires in-depth. The Orange/blk and white wires are definitely for the brake lights. These are the wires closest to the brake pedal. The orange/blk is always hot and when the brakes are not applied the white wire is dead, when the brakes are applied the white wire becomes hot with 12V.

The other plug is grey and grey/blk, and is defintely for cruise. The grey has 12V on it ONLY WHEN THE CRUISE SWITCH ON MY COLUMN IS ON. It passes the 12V over to the grey/blk wire when the brakes are not applied. When the brakes are applied the 12V dies on the grey/blk wire. However, as I said, the cruise switch must be on for the 12V source to become hot. Also, I traced that grey/blk wire over to a previously unseen 6x2 connector that's plugged into nothing at all.

Basically, the grey and grey/blk wires would technically do what I want, but they're dependent on the cruise switch being in, which is one more thing I'd rather not have to worry about. Plus, I don't know what sort of amps the TCC solenoid will draw, and the cruise switch on the column might not be ready to handle that.

The brake switch that's installed is this one seen here and here. Both of these sites specifically say this switch is for models with cruise and an auto transmission. But, after looking for myself and seeing how this wiring works, I have no idea how that's supposed to be possible when the 12V source for the only side of the switch that will work for me depends on the cruise control switch being on, which under "normal" circumstances would be off most of the time. To make matters more confusing, I found this, which the site indicates is just for cruise control release, though it does say it's for 4x4 trucks. However, I did see another slot for a 2nd brake switch that's a bit larger of a hole, and looks like this cruise control release switch may fit it.

I'd be more than happy to just remove the current cruise plug from the brake switch in lieu of my TCC plug since I don't use cruise on this truck, nor do I even know if it works, but I'm not even seeing another plug in there anywhere that could account for this type of setup, much less the type of setup that they're implying should be already in place. I'm going to try and get my camera up in there to take flash pictures in the areas I can't see so well. Maybe I'll find something hiding under there.

Any ideas anyone? What does it look like down by your brake switch? Are there 2 switches? What are your wire colors looking like?

HELP!

The_Raven · 10-31-2009, 08:21 PM

I don't have an auto, just worked with enough...

You should find a second switch on the brake pedal support bracket, for the TCC, since your truck originally had cruise. Now that you posted about the cruise stalk.

Illuminating the area you're working with, can make things more clear.

ddog800 · 10-31-2009, 09:48 PM

Yeah, I did find another spot for another switch next to the existing switch at least, but theres definitely not any other plugs up there that could be meant for the TCC.... I laid under the steering column looking up with a flashlight and my camera to get a look at those hard to reach areas for hours and saw nothing else. If only I knew someone else with a similar S10 I could take a look at it would be perfect. I was able to locate where that 6x2 cruise control plug was supposed to go to and got it plugged back in, for whatever that's worth.

At this point I'm sorely tempted to just disconnect this cruise plug on the brake switch from the rest of the cruise system and manually run wires to it and down to the TCC and be done with it, since cruise doesn't work on my truck anyway. I still have not had a chance to look for the tan/blk ECM controlled ground wire, but I could always tap something in to the wire near where it terminates at the ALDL 'F' terminal if I can't locate it. However, perhaps if I can find where the original ECM wire is going to and where it was cut at, then I'll find the TCC hot wire there with it since I'd think it would have been cut at the same place. I might break out my toner and probe I use for tracking down phone and network wiring and see if I can trace it through the harness tomorrow.

I get the feeling I'm gonna have this thing ghetto-rigged in the end whether I like it or not.

ddog800 · 11-01-2009, 07:48 PM

Well, I got everything hooked up today. I ended up just borrowing all of the wiring from the cruise system. Now that it's hooked up though, I'm getting some strange behavior. It's locking it up really early, like in 2nd gear. I can't even properly accelerate on the highway before it's locking the thing up. If I tap the brake for a sec it'll unlock it, but it locks it right back up. Not sure what could be causing this.......

ddog800 · 11-01-2009, 08:23 PM

Alright, I *think* I've gotten it. After poring over some alldata diagrams, I think I had the connector 90 degrees off. I just changed it and test drove it again, and I believe it's working much more normally. Now it doesn't attempt to lock it up until about 40 MPH and only if I'm not accelerating. I wasn't able to put a meter on the ALDL 'F' terminal to see what the voltage was looking like since it was dark, but I can defintely feel it going on and off.

We shall see how this goes.

10-28-2009, 11:35 AM	#1
ddog800 Registered User Join Date: Oct 2008 Posts: 45 Location: User is: OffLine	Trying to track down wiring for the TCC connector on my 86 s-10 blazer 2.8 2wd Hey guys, haven't had much luck anywhere else, maybe someone here knows or can look since this forum is more specific to my engine type/etc... I just had my tranny replaced with a rebuilt one on my 86 s-10 blazer 2.8 2wd, but when they were swapping it out they realized that all of the TCC wiring is missing. The old transmission had the connector hooked up with 2 wires going nowhere (were cut about 6 inches up). They were unable to find the original wiring at all coming from the harness. I'm assuming the old one was rigged up with a lockup kit or something, but the one I replaced it with isn't. I've been able to track down in schematics where the wiring is supposed to be coming from and the wire colors, but I'm having trouble tracking where they actually are under the hood. The schematics say there is a purple wire coming from the brake switch to supply 12V to the TCC, and then a tan/blk wire coming from the ECM (pin A7) which is the computer controlled ground. Unfortunately there is no purple wire coming from the brake switch, just orange/blk, white, grey, grey/wht (in 2 separate 2-pin connectors), so I'm assuming that it turns purple somewhere else. I haven't even tracked the ECM-controlled ground out of the firewall yet, though I have been able to spot it in the larger connector going into the ECM. I suppose I could try to rerun them from scratch, but that's a last resort as I'm certain the original wiring is in there somewhere. It would be EXTREMELY helpful if someone could take a look at the wiring and connector on a similar model truck as mine and just see where it leads and let me know so I can find the most likely place they would have cut it off at. Even if I knew if the wiring went toward the drivers side or passenger side would help. At this point I'm only driving in short spurts to and from work as I don't want to damage my new tranny because the TCC isn't being properly regulated. Thanks for any help you can provide!
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10-28-2009, 09:54 PM	#2
The_Raven Registered User Age: 32 Join Date: Oct 2003 Posts: 1,039 Location: The Nest User is: OffLine	Re: Trying to track down wiring for the TCC connector on my 86 s-10 blazer 2.8 2wd Don't worry too much about driving the truck. All you will lose is some gas milage. TCC is simply an "on" or "off" device, and will only lock (turn "on") at highway speeds. Does your truck have cruise control? I believe the grey and grey/wht wires are for the cruise. Look for a second switch at the brake pedal, IIRC the connector will have a pink and the purple wire you need. Last edited by The_Raven : 10-28-2009 at 09:56 PM.
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10-29-2009, 09:14 AM	#3
ddog800 Registered User Join Date: Oct 2008 Posts: 45 Location: User is: OffLine	Re: Trying to track down wiring for the TCC connector on my 86 s-10 blazer 2.8 2wd hmm, Ok, the main reason I was worried was that I was told that if I cruised at highway speeds for more than 15 or 20 minutes without the TCC being able to turn on, it would overhead my transmission and burn it up. If it's just gas mileage, I can deal with that My truck may have at one time had cruise, but it certainly has never worked for me. The brake switch does appear to have 2 plugs going to it. One has the grey wires, the other has 2 orange/blk wires and 1 white wire. Did you mean this other plug, or another switch altogether?
	[Reply w/Quote]

10-29-2009, 02:20 PM	#4
The_Raven Registered User Age: 32 Join Date: Oct 2003 Posts: 1,039 Location: The Nest User is: OffLine	Re: Trying to track down wiring for the TCC connector on my 86 s-10 blazer 2.8 2wd It's true the tranny could get warmer than it would with the TCC locked, but definatly won't burn it up. In a different vehicle, it was FWD, but had a TCC that worked on the same principle (also a GM), I had the TCC disconnected for years and did plenty of highway driving. If the truck didn't have cruise than the grey wires might be for the TCC control. One will have 12V ignition and the other will have 12V when the brake pedal is released, but not when pressed. This unlocks the TCC when the brakes are applied.
	[Reply w/Quote]

10-29-2009, 03:34 PM	#5
ddog800 Registered User Join Date: Oct 2008 Posts: 45 Location: User is: OffLine	Re: Trying to track down wiring for the TCC connector on my 86 s-10 blazer 2.8 2wd Ok, I went outside during lunch hour with a multimeter and did some digging. I was actually able to find a plug with a pink and purple wire, but it didn't have anything to do with the brake switch. It was connected to another set of wires just above the brake pedal switch. I did find 12V on the purple wire with the ignition on, but it didn't change whether I had the brake depressed or not. So, I went back to the brake pedal switch and put my meter on the white wire on one of the plugs. With the ignition on I found that I was getting nothing when the brake is not pressed, and when I applied the brake I got 12V. This sounds like the reverse of how you described that I would need it to be, so perhaps this isn't the one I need. I imagine this must be the one that powers the brake lights since it's providing 12V when the pedal is applied? I didn't have time to check the gray wires, will do that when I get off this afternoon, and I'll recheck the other ones for good measure (was kind of in a rush). Thanks very much for the help. Last edited by ddog800 : 10-29-2009 at 03:44 PM.
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10-29-2009, 06:53 PM	#6
The_Raven Registered User Age: 32 Join Date: Oct 2003 Posts: 1,039 Location: The Nest User is: OffLine	Re: Trying to track down wiring for the TCC connector on my 86 s-10 blazer 2.8 2wd Yes, the Orange(/black) and white wires are for your brake lights. The TCC switch could be a seperate switch, though it is usually built into the same switch that controls the brake lights.
	[Reply w/Quote]

10-29-2009, 10:46 PM	#7
ddog800 Registered User Join Date: Oct 2008 Posts: 45 Location: User is: OffLine	Re: Trying to track down wiring for the TCC connector on my 86 s-10 blazer 2.8 2wd Yep, and according to every related diagram I could find on alldata that's exactly where it should be coming from. Unfortunately I didn't get a chance to check it before it got dark, so looks like tomorrow's another day (if it's not pouring rain like I think it will be).
	[Reply w/Quote]

10-31-2009, 02:21 PM	#8
ddog800 Registered User Join Date: Oct 2008 Posts: 45 Location: User is: OffLine	Re: Trying to track down wiring for the TCC connector on my 86 s-10 blazer 2.8 2wd Update: OK, I just spent a little while testing all of these wires in-depth. The Orange/blk and white wires are definitely for the brake lights. These are the wires closest to the brake pedal. The orange/blk is always hot and when the brakes are not applied the white wire is dead, when the brakes are applied the white wire becomes hot with 12V. The other plug is grey and grey/blk, and is defintely for cruise. The grey has 12V on it ONLY WHEN THE CRUISE SWITCH ON MY COLUMN IS ON. It passes the 12V over to the grey/blk wire when the brakes are not applied. When the brakes are applied the 12V dies on the grey/blk wire. However, as I said, the cruise switch must be on for the 12V source to become hot. Also, I traced that grey/blk wire over to a previously unseen 6x2 connector that's plugged into nothing at all. Basically, the grey and grey/blk wires would technically do what I want, but they're dependent on the cruise switch being in, which is one more thing I'd rather not have to worry about. Plus, I don't know what sort of amps the TCC solenoid will draw, and the cruise switch on the column might not be ready to handle that. The brake switch that's installed is this one seen here and here. Both of these sites specifically say this switch is for models with cruise and an auto transmission. But, after looking for myself and seeing how this wiring works, I have no idea how that's supposed to be possible when the 12V source for the only side of the switch that will work for me depends on the cruise control switch being on, which under "normal" circumstances would be off most of the time. To make matters more confusing, I found this, which the site indicates is just for cruise control release, though it does say it's for 4x4 trucks. However, I did see another slot for a 2nd brake switch that's a bit larger of a hole, and looks like this cruise control release switch may fit it. I'd be more than happy to just remove the current cruise plug from the brake switch in lieu of my TCC plug since I don't use cruise on this truck, nor do I even know if it works, but I'm not even seeing another plug in there anywhere that could account for this type of setup, much less the type of setup that they're implying should be already in place. I'm going to try and get my camera up in there to take flash pictures in the areas I can't see so well. Maybe I'll find something hiding under there. Any ideas anyone? What does it look like down by your brake switch? Are there 2 switches? What are your wire colors looking like? HELP! Last edited by ddog800 : 10-31-2009 at 02:23 PM.
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10-31-2009, 08:21 PM	#9
The_Raven Registered User Age: 32 Join Date: Oct 2003 Posts: 1,039 Location: The Nest User is: OffLine	Re: Trying to track down wiring for the TCC connector on my 86 s-10 blazer 2.8 2wd I don't have an auto, just worked with enough... You should find a second switch on the brake pedal support bracket, for the TCC, since your truck originally had cruise. Now that you posted about the cruise stalk. Illuminating the area you're working with, can make things more clear.
	[Reply w/Quote]

10-31-2009, 09:48 PM	#10
ddog800 Registered User Join Date: Oct 2008 Posts: 45 Location: User is: OffLine	Re: Trying to track down wiring for the TCC connector on my 86 s-10 blazer 2.8 2wd Yeah, I did find another spot for another switch next to the existing switch at least, but theres definitely not any other plugs up there that could be meant for the TCC.... I laid under the steering column looking up with a flashlight and my camera to get a look at those hard to reach areas for hours and saw nothing else. If only I knew someone else with a similar S10 I could take a look at it would be perfect. I was able to locate where that 6x2 cruise control plug was supposed to go to and got it plugged back in, for whatever that's worth. At this point I'm sorely tempted to just disconnect this cruise plug on the brake switch from the rest of the cruise system and manually run wires to it and down to the TCC and be done with it, since cruise doesn't work on my truck anyway. I still have not had a chance to look for the tan/blk ECM controlled ground wire, but I could always tap something in to the wire near where it terminates at the ALDL 'F' terminal if I can't locate it. However, perhaps if I can find where the original ECM wire is going to and where it was cut at, then I'll find the TCC hot wire there with it since I'd think it would have been cut at the same place. I might break out my toner and probe I use for tracking down phone and network wiring and see if I can trace it through the harness tomorrow. I get the feeling I'm gonna have this thing ghetto-rigged in the end whether I like it or not.
	[Reply w/Quote]

11-01-2009, 07:48 PM	#11
ddog800 Registered User Join Date: Oct 2008 Posts: 45 Location: User is: OffLine	Re: Trying to track down wiring for the TCC connector on my 86 s-10 blazer 2.8 2wd Well, I got everything hooked up today. I ended up just borrowing all of the wiring from the cruise system. Now that it's hooked up though, I'm getting some strange behavior. It's locking it up really early, like in 2nd gear. I can't even properly accelerate on the highway before it's locking the thing up. If I tap the brake for a sec it'll unlock it, but it locks it right back up. Not sure what could be causing this.......
	[Reply w/Quote]

11-01-2009, 08:23 PM	#12
ddog800 Registered User Join Date: Oct 2008 Posts: 45 Location: User is: OffLine	Re: Trying to track down wiring for the TCC connector on my 86 s-10 blazer 2.8 2wd Alright, I think I've gotten it. After poring over some alldata diagrams, I think I had the connector 90 degrees off. I just changed it and test drove it again, and I believe it's working much more normally. Now it doesn't attempt to lock it up until about 40 MPH and only if I'm not accelerating. I wasn't able to put a meter on the ALDL 'F' terminal to see what the voltage was looking like since it was dark, but I can defintely feel it going on and off. We shall see how this goes.
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