TCC unlock wire

[Leeztruk]

I'm about to install a 5.3/4L60e combo into my '89 Cheyenne. I'll be using the LS stand alone harness and PCM, so the truck's ECM and harness won't be in the picture. What I need to find is the TCC unlock wire from the brake pedal switch. Would that be the purple wire on the switch? I actually have the truck's wiring manual, but it's hard to decipher, and this brake pedal switch is weird, unlike the earlier trucks/cars that had a simple two part plunger style switch with a NO/NC set of contacts. Thanks

 

[Leeztruk]

Actually answered my own question; The purple wire is, indeed, the tcc power wire. The switch (once I got it out) was easily understood when it was in my hand. It is comprised of 2 internal switches, one normally open, one normally closed. Orange and white wires on the NO side, pink-white/purple on the NC side. Orange, and pink-white are constant hot

 

[eran tomer]

how do you get the switch out? it's bearly visible without removing the steering column.

 

[Komet]

The purple TCC unlock wire is much easier to access underneath the glove box where it connects to the other connector. If you're doing a PCM swap you'll already be in that area. Speedo and tach are also right there.

 

[Supercharged111]

The purple TCC unlock wire is much easier to access underneath the glove box where it connects to the other connector. If you're doing a PCM swap you'll already be in that area. Speedo and tach are also right there.

For a TBI truck, sure. Not so much on something that started life as a Vortec truck.

 

[Komet]

For a TBI truck, sure. Not so much on something that started life as a Vortec truck.

That's why Vortec trucks are parts donors

 

[eran tomer]

The purple TCC unlock wire is much easier to access underneath the glove box where it connects to the other connector. If you're doing a PCM swap you'll already be in that area. Speedo and tach are also right there.

so after I retrieve this wire what do I do with it? I have a PSI harness and pcm and the instructions aren't clear.

 

[Komet]

so after I retrieve this wire what do I do with it? I have a PSI harness and pcm and the instructions aren't clear.

You should have a wire that takes in brake switch input for the torque converter somewhere. The truck supplies 12v when the brake is not pressed, and no voltage when the brake is pressed.

 

[eran tomer]

You should have a wire that takes in brake switch input for the torque converter somewhere. The truck supplies 12v when the brake is not pressed, and no voltage when the brake is pressed.

and this would be the purple wire under the glove box?

 

[Leeztruk]

Eran, that purple wire just transfers or interrupts 12vdc to the ecm/pcm for it to determine if/when to apply/disengage TCC. So, when you find your purple wire, wherever it is, just severe it before the truck's original computer, and attach your new harness TCC wire to the switch side of the truck's TCC wire. Your new PCM will take care of the rest. Good luck with your swap. BTW, that switch I showed earlier, is actually pretty easy to install/remove once you get to it. You may have to be a contortionist to get to it, but it's doable