[Fat Charlie]

I showed your question to one of the techs. He said you're going to have to tap into the wiring harness somewhere no matter what, and you're going to set codes because it's going to be locked up when the car isn't telling it to lock up. He also said that if you leave it locked when you go into first or reverse then you're going to have problems. When a tranny guy at the dealership says you're going to have problems, they're problems you don't want.

The solenoid that you're going to be switching controls the solenoid switch valve, which directs the fluid to either the low/reverse clutch or the torque converter. So you need to make sure that the torque converter is unlocked before you need something lower (or reverse), and for safety you shouldn't lock it until you're at least in third. Through all this, he said that you need to control the ground side of the solenoid because it needs 12 volts at all times.

I rearranged some of what he said for clarity and I don't understand the electrical bit but it sounded important.