Step 1 - Build the dummy load:
A quick look at the wiring diagrams and diagnostic sections for the 4EAT shows this page:
Side Note: I've included pictures of all the relevant info you'll need, but you really should get a copy of the Factory Service Manual (FSM) for yourself - they're free, AND there's a download link at the top of this forum.
http://www.rs25.com/forums/showthread.php?t=73249
If you have the FSM, the relevant information can be found here:
DIAGNOSTICS SECTION/Automatic Transmission and Differential/Diagnostics/Transmission Control Module (TCM) I-O Signal.pdf
/page3
Over on the far right we see that the solenoid presents between 10-17 ohms of resistance.
Consequently, this is the number that the TCM expects to see when the solenoid is functioning properly. Above or below that number by too much and the TCM will throw a fault code. This means that we need to install a resistor that behaves in a similar way. The easiest way to do this is to go buy a 10-25 watt, 10-17 ohm resistor. Unfortunately you won't find one of those down at your local Radio Shack - that's just too specific - you're going to need to build a custom setup. Now, there are a bazillion ways to wire up resistors to get the results you need. I'm not going to go into gory details about ohms law, and all the options unless asked to do so. Suffice it to say that if you buy what I listed above, and build it as I instruct, you'll end up with a dead-sexy 10watt, 17ohm resistor.
Let's build it -
First I like to check each of the resistors to make sure they are working properly. Set your multimeter to check impedance (ohm symbol - looks like a horseshoe) and test each resistor by touching the probes to the leads of the resistors (polarity doesn't matter here). Ideally you'll see a number close to the rating of the resistor - in our case 50 and 100 ohms.
If everything checks out, grab your perfboard, and mount your resistors by pushing the leads through the holes and gently bending them to hold everything in place. Now would be a good time to add some little pieces of heat shrink tubing to the exposed leads on the resistors (see later pics). Mock everything up and make sure you're happy before moving on.
You'll notice I have my resistors mounted in a set of heat sinks. Again, you don't have to do this - I'm a bit obsessive and tend to overbuild things, plus I had them laying around.
At this point I like to mark the locations of the resistor leads, and in my case the heat sinks. After you've marked everything - disassemble or at least pull everything away from the board an inch or two so you can get the glue gun in there.
Now take your hot glue gun and put a bead where each resistor body is going to rest on the perfboard and quickly push the resistor back in place. This will firmly attach the resistor to the perfboard so it won't vibrate out over time. Repeat for the rest of your resistors and whatever else you may have.
Now it's time to solder up the electrical connections on the back side. Now's a good time for a quick electronics tidbit: We're wiring these resistors in what's known as a "parallel circuit" as opposed to a "series circuit". I'll skip the mumbo jumbo, and math about why, and just say that I like the idea of having multiple resistors to share the load. These things get pretty warm during use, and more surface area to dissipate heat is always a good thing.
What I did was to cut and strip three separate pieces of wire for each set of leads - you can just run one continuous uninsulated wire as well - just make sure you insulate it against shorting out somehow - even electrical tape is better than nothing. Regardless of you wire choice run a wire up one side, and down the other. Now nolder each of the resistor leads to the wire and you're done.
Do NOT bridge the leads of any single resistor - just connect all the leads on each side. When you're done soldering, snip the excess resistor leads - you don't need anything past the actual solder joint.
Now it's time to check the overall impedance of your finely crafted dummy load. Just like before, put the probes of your multimeter on the leads of the first resistor. Only this time, since the resistors are all part of the same circuit, you should get a cumulative reading of all the resistors. If you've done it right, and your resistors were within their specs, the number should be very close to 17ohms.
If so, your dummy load is complete - congratulations. Have a bite to eat and a soda to celebrate, because now it's time to head out to the car - which only means lots of contortions under the dashboard.
Next - how to run wire in a car....upside down!