It is powered by the actual solenoid signals; I made plug-in-between breakout splitter; so after separating tranny to underhood harness cnnector, I can just plug my device in.
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If I don't need to watch it, I can unplug it or just hide it under hood, thanks for the magnet I put at the bottom.
If you have ECT transmission unplugging the harness should put transmission in to the "manual shift mode"; "second" position of the lever will put it into "D"-third gear; applying 12 volts to the lock-up solenoid pin (yellow round connector) will apply the lock up . The solenoid has 15 ohms resistance so I would suggest to use 5 Ohm 4 watt resistor in series with it just in case (the computer output voltage is about 11.5 v vs 14 volts when engine is running).
I did similar thing on my friend's car to isolate the torque converter noise.
In the first gear the lock up cannot be applied because 1-2 shift valve block the lock -up apply passage in the valve body