Slushy Jeep (Freezing the Slushbox at least)

[Joenavy85]

Has anybody done a TC lock up switch on a KJ('02-'07) Liberty with a 42RLE trans? I'm wanting to do it on my Jeep, but don't want to risk destroying the wiring harness in the process.

[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.

[Joenavy85]

I'm only looking to lock it up for engine braking (while simultaneously killing power to the fuel injectors) at highway speeds, and have no intentions of locking it during city travel. did he happen to say where the wiring is for me to tap into?

[Joenavy85]

And I know I have to tap into the harness, I just don't want to have to go wire by wire to find out which one is for the TC, like it says in the Wiki on how to do it

[Fat Charlie]

The easiest place is apparently at the PCM. It has 4 connectors: black/black, black/orange, black/natural and black/green. You want C4, the one with the green tab. Pin #10 is the ground side of the low/reverse solenoid.