Torque Converter lock up

[Hart_Rod]

I was reading online that the E38 computer uses the brake switch to control TC lockup different than older computers - it received power when the brake lights receive power unlike the older systems that were opposite. Can anyone confirm this? Thanks,

Rob

[Hart_Rod]

Ok, apparently they are opposite....@#$%^&*()%$%^&*(......this probably explains the issues I was having the weekend with it not wanting to idle when put in gear....2 days worth of tuning down the drain.....

[BR3W CITY]

So THATS what you meant in your text. I thought you meant it was wired backwards (happened to me).

[Hart_Rod]

Originally Posted by BR3W CITY

So THATS what you meant in your text. I thought you meant it was wired backwards (happened to me).

LOL, I'm not so good at texting....

[oldman3]

Originally Posted by Hart_Rod

LOL, I'm not so good at texting....

I've never texted and don't want to learn (I'm old)...Jim

[Houston Ben]

Oh Crap!! I might have done mine wrong, here is what I did from LT1swa.com

Brake Switch Signal - For automatics with lock up converter, the PCM needs signal when brake pedal is pressed. However, the signal needed is opposite how you're brake lights work. The PCM wants 12v+ constant on this wire when brake IS NOT pressed, and OPEN Circuit when the brake IS pressed. If you vehicle was equipped with a lockup trans to begin with, you probably already have the proper normally closed switch mounted by your brake light switch. If you do not, you can use a relay to perform the same thing. On most relays, there are 5 terminals, 2 of them turn the relay ON when provided ground/power. There are then a normally open leg and a normally closed leg on the relay and a supply. By feeding 12v+ on the supply leg, and hooking the Brake Switch Signal wire to the normally closed leg, you will now have the correct signal for the PCM. When the brake is pressed, 12v+ flows to brake lights, tap into this wire, and run it to the relay to turn the relay on. This will cause the normally closed leg to become open, thus turning OFF the 12v+ signal to the PCM. When you release the brake pedal, the relay will turn OFF, and then feed 12v+ to the PCM.

Did I screw the pooch in this one?

[Houston Ben]

Here is how I hooked my relay up, is it correct?

[Hart_Rod]

Originally Posted by Houston Ben

Here is how I hooked my relay up, is it correct?

If your computer is a E38 like mine (and I'm pretty sure it is), that's the wrong way. The new computers want power when the brake pedal is pressed, not when it is not being pressed.

[Billett]

Originally Posted by Houston Ben

Here is how I hooked my relay up, is it correct?

Is this the correct way to wire a gen iii then?

[Hart_Rod]

Wire it like this:

[68c10airstream]

Hi Rob, on the wiring of the relay #85 should go to ground and #86 go to 12volts +. This is following DIN wiring guidelines. By switching them around the relay still works, but won't potentially have a voltage spike put on line. Years ago some relays used a voltage spike protection diode in them and if wired as you showed with #85 going to + and #86 to - i have glitche captured as high as 60 volts induced on-line when a relay turns off if the diode was defective or wired incorrectly. I believe all newer relays use a resistor across 85/86 so polarity doesn't matter. If you use a good volt meter do a diode test on the 85/86 relay terminals with it out of the circuit and in your hands. Put the red and black leads on way, note reading, flip the leads and note the reading and if the same it's resistor equipped, if not it's diode equipped. Think of it as an ignition coil, and you saturate the windings with electricity and when you open the circuit the electricity will go some where. That voltage spike can ruin expensive equipment! Just trying to be helpful to others, not finding fault! I feel if i can share some of my prior career and make their job go easier and learn something along the way GREAT! Good luck, Brian F.

[Houston Ben]

Hart Rod, isn't that the same one I put up that you just told me was incorrect?? Here is how I have mine set up:

My relay is set up just like the picture above with #85 on the relay connected to the wire on the brake pedal that when pushed the brake lights come on. So when the brakes are hit the relay gets power.

There were two wires to the brake switch an orange one and white one. The orange is "hot" at all times, the white is only "hot" when I push on the brake and that is the one I tapped into.

So when you stated

The new computers want power when the brake pedal is pressed, not when it is not being pressed

I think we are on the same page but please correct me if I am wrong as I don't want to screw anything up. Just trying to get this straight in my head lol.

[Hart_Rod]

Originally Posted by Houston Ben

Hart Rod, isn't that the same one I put up that you just told me was incorrect?? Here is how I have mine set up:

My relay is set up just like the picture above with #85 on the relay connected to the wire on the brake pedal that when pushed the brake lights come on. So when the brakes are hit the relay gets power.

There were two wires to the brake switch an orange one and white one. The orange is "hot" at all times, the white is only "hot" when I push on the brake and that is the one I tapped into.

So when you stated I think we are on the same page but please correct me if I am wrong as I don't want to screw anything up. Just trying to get this straight in my head lol.

Look at the 2 diagrams, they are slightly different. Yours has the 12V+ wire going to 87a and mine has it going to 87. So all you should have to do is switch the connector from 87a to 87 and you should be good to go.

[Custom 68]

I just bought a 2 way switch so it is wired up normal for the brakes but the other side is hot when the brake pedal is up then it "breaks" the circuit when the brakes are applied. I don't know the part number but anything with Cruise works the same way. I will dig to see what I did if you need me too. I didnt need or use any relays for the switching.
I did my swap about 8 or 9 years ago before they were all being done so I had to do alot of digging to get all the right pieces.
Dave

[Hart_Rod]

Originally Posted by Custom 68

I just bought a 2 way switch so it is wired up normal for the brakes but the other side is hot when the brake pedal is up then it "breaks" the circuit when the brakes are applied. I don't know the part number but anything with Cruise works the same way. I will dig to see what I did if you need me too. I didnt need or use any relays for the switching.
I did my swap about 8 or 9 years ago before they were all being done so I had to do alot of digging to get all the right pieces.
Dave

Dave - that switch works great for the GEN III and older computers, but for the GEN IV (E38 and newer) Chevy in their infinite wisdom decide to change how the torque converter is "triggered". Now it is triggered "+" when you push the pedal, not triggered "-".

[Houston Ben]

Hart Rod, Yup, I missed that, well the good news for me (maybe) is I used a 4 pin realy and not a 5 which hooks it up to #87. Is this good Hart Rod, or do I need to use a 5 pin relay??

Thanks for all your help!!!!!!!!

[Hart_Rod]

Originally Posted by Houston Ben

Hart Rod, Yup, I missed that, well the good news for me (maybe) is I used a 4 pin realy and not a 5 which hooks it up to #87. Is this good Hart Rod, or do I need to use a 5 pin relay??

Thanks for all your help!!!!!!!!

You should be good. I would just double check that you have power going to the TC when the pedal is pushed and no power when you release the pedal.

[jorgensensc]

Ok hart! You may have just figured out something that I didn't know. My only understanding on the e38 was that early e38 didn't tell the TCC to lock up, they got a signal from the brake switch. Later e38 told the TCC to lock up directly. I used the cruise brake switch on mine, so mine may be wired backwards. So if it is, do you think that is possibly why my dyno numbers felt low and the ECM is giving me the p0606 code? Would explain why the engine feels a little boggy sometimes.

[Hart_Rod]

Originally Posted by jorgensensc

Ok hart! You may have just figured out something that I didn't know. My only understanding on the e38 was that early e38 didn't tell the TCC to lock up, they got a signal from the brake switch. Later e38 told the TCC to lock up directly. I used the cruise brake switch on mine, so mine may be wired backwards. So if it is, do you think that is possibly why my dyno numbers felt low and the ECM is giving me the p0606 code? Would explain why the engine feels a little boggy sometimes.

Shawn - the trigger being wired could/ will have some effect on the engine power. If it's slipping when it should be locked, then you will have reduced power. Good question on the code. That code refers to a PCM/ECM failure or a possible problem with the operating system not matching the throttlebody.

http://forums.trailvoy.com/showthread.php?t=60767

http://forum.efilive.com/showthread....ody-inop/page2

http://forum.efilive.com/showthread....and-tbody-inop

[jorgensensc]

Rob,
Where did you read about the ECM wanting 12 volts for TCC lock up? I can't seem to find that info anywhere and the alldata doesn't seem to show very clearly that the ECM receives 12 volts for lock up. At least not where I can see. Please direct me so I can figure mine out.

[Hart_Rod]

Originally Posted by 68c10airstream

Hi Rob, on the wiring of the relay #85 should go to ground and #86 go to 12volts +. This is following DIN wiring guidelines. By switching them around the relay still works, but won't potentially have a voltage spike put on line. Years ago some relays used a voltage spike protection diode in them and if wired as you showed with #85 going to + and #86 to - i have glitche captured as high as 60 volts induced on-line when a relay turns off if the diode was defective or wired incorrectly. I believe all newer relays use a resistor across 85/86 so polarity doesn't matter. If you use a good volt meter do a diode test on the 85/86 relay terminals with it out of the circuit and in your hands. Put the red and black leads on way, note reading, flip the leads and note the reading and if the same it's resistor equipped, if not it's diode equipped. Think of it as an ignition coil, and you saturate the windings with electricity and when you open the circuit the electricity will go some where. That voltage spike can ruin expensive equipment! Just trying to be helpful to others, not finding fault! I feel if i can share some of my prior career and make their job go easier and learn something along the way GREAT! Good luck, Brian F.

Makes sense. That diagram came from the LT1tech.com website. The "safer" way to wire it is as you described. Thanks!

Originally Posted by jorgensensc

Rob,
Where did you read about the ECM wanting 12 volts for TCC lock up? I can't seem to find that info anywhere and the alldata doesn't seem to show very clearly that the ECM receives 12 volts for lock up. At least not where I can see. Please direct me so I can figure mine out.

Shawn - in the instructions for my Speartech harness it says that the TCC wire should receive power when the brake is pushed. I also found this on HPTuners:

http://www.hptuners.com/forum/showth...a-break-signal

Hope this helps.

[jorgensensc]

Ok Rob! I may just owe you one! I redid the wires using a relay and the diagram you provided. The truck seems to run differently. Seems to run much better. Better off the line and mid throttle response. May be my imagination, but.... The most important thing is I haven't had the p0606 code again. I did everything that I normally do to make it happen, but it hasn't occurred. Could be coincidence, but I hope not. Keep your fingers crossed!
Shawn

[Hart_Rod]

Originally Posted by jorgensensc

Ok Rob! I may just owe you one! I redid the wires using a relay and the diagram you provided. The truck seems to run differently. Seems to run much better. Better off the line and mid throttle response. May be my imagination, but.... The most important thing is I haven't had the p0606 code again. I did everything that I normally do to make it happen, but it hasn't occurred. Could be coincidence, but I hope not. Keep your fingers crossed!
Shawn

Sweet! Keep us updated.

[Hart_Rod]

Originally Posted by jorgensensc

Ok Rob! I may just owe you one! I redid the wires using a relay and the diagram you provided. The truck seems to run differently. Seems to run much better. Better off the line and mid throttle response. May be my imagination, but.... The most important thing is I haven't had the p0606 code again. I did everything that I normally do to make it happen, but it hasn't occurred. Could be coincidence, but I hope not. Keep your fingers crossed!
Shawn

Any updates? Has the code reappeared?

[jorgensensc]

Unfortunately the code came back. But the truck definitely drives different, better.