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Can lockup be defeated via wiring?

idrivejunk

idrivejunk

New member
99 GTP, 323K DD. Remember me? I've had no changes.

Oscillation gets on my nerves something fierce.

Potential causes and solutions and diagnosis aside...

Dad put a toggle switch on the torque converter lockup in his '80 Citation. I want to do that.

Or without a switch. My usage does not involve any speed limits over 45 MPH so lockup is not wanted or needed.

So can I stop the madness by wiring alteration? Looking at a PCM connector image found here, I see a TCC brake switch input and a TCC release input. Not finding anything showing brake switch wires.

I am a bodyman, poor at electronics. Pulling the TCC fuse ain't what I want, I know that much. Can you help me reduce experimentation? I did research here but only found talk of how to tune out lockup.

TIA

​Matt
 


Never mind. I switched up search terms and am finding more discussion. The answer I want to hear would be wrong.
 
I swapped in a brake switch from an 02 in case that was it. Nope.

I unplugged the rear connector (4 wires) from the lower switch at the brake pedal. No more lockup but also no cruise.

Anybody know what the rear four wires are? Stakes are too high and odds are too long to start guessing combinations and unpinning or jumpering but I would like to keep cruise.
 
Torque converter clutch relies on a ground signal from the PCM at pin "T" on the case connector.

Logically, it would make sense that if you pulled the "T" wire from the connector, you would get the desired result (no TCC lock). You may need to ground that wire (from the PCM) to make the PCM happy, so it's not an open circuit. I don't know.

You may also be able to wire in a switch to ground on that "T" pin to make it manually controlled ON/OFF vs the computer control and PWM.

This is all just thinking out loud. Experiment at your own risk! :th_scratchhead:
 
The experiment was already done via trial and error although obviously I cannot speak as to long term effects. I established that on the brake switch, the four wire connector is for cruise and TCC. By unplugging it, I got the desired result. But that kills cruise. So to me, it stands to reason that two of the four are for cruise and two are for TCC. If only I knew which were which, I suspect I can reconnect two of the four wires there to get cruise back.

Wierdest thing... that no diagrams are out there which identify wires going to the brake switch. I can't find anything and that seems odd. Like anything I attempt... it seems no one has ever run into the same questions or had a similar train of thought.

All I want is that info now. Where the wires go that are in the 4 pin connector at brake switch.

Thanks, Brandon. Any idea where to find the info? Somewhere at some point a schematic must have existed. Camaro (and probably the rest of GM) switches appear to use the same connector configuration. Theres just no clues to find, about what the wires there do.
 
A "bandaid" for the TCC oscillation is to raise the min. TCC pwm duty cycle percent by 5-15%, I did this to my 2000 GTP 14 yrs ago, still working good, however if your in the mountains and start to load in overdrive up a hill, it will slightly oscillate, so I just kick it down a gear.

Hope this helps.
 


The answer to the title question is: Yes, but not while retaining cruise control. Remove purple wire from blue connector on brake switch.
 
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