Once your harness is all loomed up you can go ahead and permanently install it into the engine bay.
This post is assuming you bought a quality harness. They will all come with super detailed installation instructions and each of the ends with delphi connectors will have labels on them. Unfortunately its been a few months since ive done this and i wired the entire truck up and cranked it up in one day, so i dont remember every single wire connection that i made but ill do my best to recall what i can. If you have all of the supplies you need on hand, from this point until you hit the first crank, you should be able to knock this out in one day. Perks of getting a good wiring harness. There are also quite a few different options with this like gps speedo and aftermarket tach, etc so ill just kinda be going into what i did, which was kept all the stock stuff.
Most of these stand alone harnesses use the same wire colors and pinouts for everything to mirror the stock GM harness, whatever harness you use, use the manual that comes with it. That being said I used the painless performance Gen3 motor with 4l60/4l80 and drive by wire.
Here is the installation instruction PDF to give you an idea of what to expect in this post.
Anyways, Tuck the wires as best you can on either side of the motor for the fuel injectors, ECT, Alt, MAF, etc. Go ahead and install every single delphi connector on your harness that attaches to the motor. You can hold off on the starter and stuff going back down the transmission for now, just let that dangle.
Once everything is connected (dont connect the PCM yet) go inside your truck and remove the driver side kick panel. I went ahead and completely removed the emissions control box and like 10 runs of unused wires. Be sure to double check the Wiring diagram posted in the following post to be sure it is safe to remove the wires. When you terminate a wire use the marine heat shrink on the exposed wire end, heat it to shrink and squeeze the glue for a good bond.
After you remove the emissions control box youll have a nice convenient bracket available and a large empty space against the wall behind it. Youll use this space for 3 relays for cruise control a little later and a dakota digital tach box if youre keeping your stock tach.
Dont be intimidated when youre looking at a view that looks like this...
Next Youll need to run the cluster of wires through your old clutch master cyl hole and into the cab of the truck. If you angle the Gas pedal plug just right it will fit through the clutch hole. You will need to depin the OBD2 plug to get the wires through though. Just take pics of the back of it and use your handy delphi tool to do it and repin it once the wires are through.
Mount your obd2 plug next to your hood release on the bracket. Then if your harness came with a check engine light you can either just use that one, or piggyback off of the wiring for that light up to your now unused choke light. I just cut and spliced the wires with the open barrel crimps up near the bulb. Terminate the old wires with marine heat shrink. From here you will want to take the strongest rubbing alcohol you can get and rub the words CHOKE off of the choke light housing. Then contact Mo Faraz for a dry transfer decal with the OEM toyota engine graphic and the word CHECK. I measured this with calipers to guarantee that they fit before he designed them.This will now be your check engine light.
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From here you will need to make a few various connections. Youll need a right angle drill or impact attachment to open up the hole for your brake pedal switch and install a GM D850A brake pedal switch. When you are done, go back and adjust this switch so the brake lights come on with a little bit of extra brake pedal travel, i mean a little, after it contacts the switch. If you adjust this switch to turn your brakes on with not enough stroke, your cruise control wont work
Install some fully insulated female connectors to the Pink, purple, and light blue wire from your standalone harness and connect them. Light blue will be to your brake lamps. The 4th wire is a 12v + wire. All of this should be in your instructions with your harness.
Youll also make a few other connections that are all in the instructions here are a few off the top of my head:
-fuse block ignition is just switched 12v.
-White Tach wire will either go to your dakota digital box or your tach if you are using aftermarket tach. If you are using the stock tach, youll run the white wire from the standalone harness to the tach input of the dakota box, run a switched 12v to the box, a ground to the box, and a wire from the hi vlt tach output of the box to where the red wire attaches to the back of your tachometer itself. The settings on the dakota box will be 4cyl input, 6 cyl output and high voltage output. I used industrial velcro to mount this box to the free bracket where the emissions control box used to go. It holds up really well just clean the metal really well before sticking the velcro because its bound to be dusty. Dont permanently mount the box yet, youll need to run wires for the cruise relay under the bracket.
-I kept my mechanical speedo so didnt need the vss wire for the speedo so i terminated it just in case i ever change it out.
- AC Request wire will need to be spliced in up by the hvac controls I cant remember which wire I used, i THINK it was yellow, but definitely double check the EWD. You want this to be a 12v + wire.
-Cruise control will be brown gray blue and grey black. These will connect to whatever controls you use. Ill make a separate post on what i did for cruise
Just honestly follow the instructions closely. Thats all I did for this stuff and i had no issues. A few things to note,
-youll need to remove the starter to install the crank position sensor. it also makes it easier to install the starter B+ and Starter Sol wires
-if you used the Marks4wd water temp and oil pressure adapters youll just splice these into your toyota oem harness and theyll send signal to your gauges.
-You need to have good grounds. I did the grounds from the standalone harness to the back of one of the heads, battery to body reusing my old ground strap, then used the other side of it to connect to the frame so youll have frame to body ground. Youll also need to ground the engine to the frame.
My motor came with the Battery + box on the side of the alternator bracket on the driver side. I trimmed the bracket and flush mounted the battery+ box to the alternator bracket and ran and tucked a new loomed + wire up below my TB and to my starting battery on the passenger side. IF you do it right you wont be able to see it. You can do this many different ways.
The tail side of the wiring harness just plugs in. Youll only need to connect the long grey wire for your fuel pump, splice the long green wire from the standalone harness to your backup light (red black i think. Again look this up) wire at the plug on the old toyota harness. This is also a good time to replace these crusty wire connectors with delphi GT150 waterproof connectors. This is also a great time to use some of your woven split loom to cover all of these wires up and make them look nice and tidy.
4x4 light should just be on the transfer case.
For the two Toyota harnesses on either side of the engine bay, remove the wires you are not using and reloom the runs. Im pretty sure i just spliced the toyota ac wire to the gm ac compressor connector. The LC side is a single + wire on the chassis harness, not the engine harness. The LS connector is 2 wire, use the power wire for one of the two wires and the other side goes to ground. I also reused the fusable link wires on the passenger side so it wouldnt disturb the rest of the toyota wiring. Youll keep your side marker, headlights, and turn signal wiring too. Loom all of this stuff up really pretty, then run them behind your fenders never to be seen again. You can pull the AC wire, fusable link and other wires you kept out of the hole halfway down the fender and run it down to the compressor so you have half of the wiring hidden. The driver side will just run into the hole for the carb fan and the passenger side will run behind the washer bottle. Connect the lights on the end of the toyota harness and those are good.
If you are using Electric fans, you will want to use a separate harness for them. I used a SPAL brushless wiring kit to go with my brushless fan,
This is the wiring diagram for the kit I used. This kit uses its own temp sensor to control when the fan comes on. It makes it really easy to set up, however you also need to tell the fans to turn on when your AC is on. Youll use the optional override switch wire (blue on this harness) to connect to your PCM for the computer to tell the motor to idle up and to tell the fan the AC is on and to turn on. For Gen 3 installs, ill make a separate post for this. I believe its much much easier on Gen 4, but i am unsure what youll need to do to make it work. The motor will work without idle up for the AC, but its worth spending a little extra time to get your stuff set up to run correctly.
Once all of this is connected (everything except AC and cruise) you should be able to connect your pcm plugs and fire it right up. If you followed the instructions closely, made good connections, followed the ewd and avoided connecting 12v to ground wires... it should fire right up on the first crank. It will be okay to crank without O2 sensors installed. Gotta say, savor this moment. That first crank feeling on your first or any engine swap is freaking unmatched.
Sorry this post isnt as detailed as the others, its just been a really long time since ive done this and its hard to recall everything from memory. The plan was to knock this out in a day because i was really far behind schedule on my swap, so i didnt document it as well as i should have. If you get stuck, or have any questions feel free to shoot me a message and ill help the best i can
Once you are done with all of the wiring, go back through and look at every wire run and make sure theres no exposed wires touching anything. This is what your loom is for. You will want to go under the trans and zip tie or use adel clamps to tidy up the dangling wires and route everything and just clean it all up. Same with under your kick panel. Tuck stuff up out of the way and safe from heat and moving parts and out of eyesight. You dont want any wires visible at first glance if you can manage it.
