Harness Connectors Firewall End Of Engine Harness Above is a list of various plugs and harness connectors that connect a 3sge engine wiring harness to the rest of the car. These are the connections that your new engine will have to connect to. Below is a detailed look at how various wires and plugs were traced and other considerations that need to be made when upgrading to a 3sgte. So you got a 4th gen and you want to stuff a bit more power in it with a 3sgte. What you need -3sgte -3sgte engine wiring harness and all the sensors/electronics that connect to it (afm/maf, coil, igniter, AC sensors, O2 sensors, water temp, oil pressure, ECU........ ) -all intercooler bits -downpipe If your starting with a GT or All-Trac your good to go If you have a GTS your starter is probably going to be under the exhaust manifold where the new turbo is going to be so your going to need to modify your tranny to accept a GT or All-Trac starter and you will also need the clutch and flywheel from the GT or All-Trac, you can also find the clutch flywheel and starter on camry's. Other option is to replace the tranny with a GT or camry tranny once again you will also need the clutch flywheel and starter. So now your ready to get going. Right now you should be looking at a 3sgte engine wiring harness that has all its plugs connected to bits you got with the engine except for a few plugs at one end of the harness that connect to the battery and engine bay fuse box. The following picture shows a 4th gen 3sge engine wiring harness battery end. You will need to take some of these plugs and splice them into your 3sgte harness so your 3sgte harness can plug into the 4th gen engine bay fuse box. 2B, 2C, 2G, 2H are the only plugs you should need from your old 3sfe,3sge engine wiring harness, all the other plugs ont the engine wiring harness are engine related the only exception I can think of is 2 plugs for the tranny for a speed sensor and reverse indicator. If you got an ST165 engine to install your good to go its all just plug and play. The ST165 3sgte engine wiring harness has plugs 2B, 2C, 2G, 2H allready on it so you don't have to splice anything just plug the ST165 engine wiring harness into the 4th gen engine bay fuse box. You may have to wire up the intercooler pump as I'm not sure if its on the engine wiring harness or engine bay wiring harness but other than that putting in an ST165 engine is going to be the easiest. If you want to put in an ST185, ST205, ST215 engine your going to have to modify the new engine wiring harness to plug into the 4th gen engine bay fuse box. These should be the only connections on you new harness that don't connect to a part of your new engine or electronic bits that came with the engine. So we have to look at the 4th gen engine bay fuse box It does not matter if you have a GT GTS or All-Trac all the fuse boxes are the same. GT & All-Trac fuseboxes are identical GTS fuse boxes look slightly different but all the plugs/locations are the same. Heres whats going on inside the fusebox. So what we need to do is identify what the wires for the 4 plugs are for Plug 2B Plug 2C Plug 2G Now that we know what the plugs and wire colors are we need to check the electrical diagrams to see what the wires do. closeup In this case I'm going to start looking at Plug 2B Pin 1 red - 12 volts coming out of the fuseable link box Pin 2 white - 12 volt 40 amp AM1 fuseable link Pin 3 white - 12 volt 40 amp AM1 fuseable link Pin 4 black with red stripe - 12 volt 30 amp AM2 fuseable link Pin 6 yellow - "L" terminal of the altenator Plug 2C Pin 1 green with black stripe - A/C high pressure switch(radiator fan) 3sge Pin 3 white with black stripe - circuit opening relay pin6, air flow meter pin 2, vsv(for engine idle up) pin 1, cruise control vacuum pump, cruise control vacuum switch, cruise control switch(comb. sw) Pin 4 green with black stripe - Pin 6 black with white stripe - A/C magnetic clutch Plug 2G Pin 2 pink - TCCS ECU pin 2 Pin 3 black with orange stripe - plug 2G pin 6 Pin 4 yellow - charge warning light (combination meter) Pin 5 black with yellow stripe - circuit opening relay pin 2, TCCS ECU pin 14, TCCS ECU pin 13,check connector pin 12, oxygen sensor pin 2, vsv (for T-vis) pin 2 Pin 6 black with orange stripe - plug 2G pin 3 Plug 2H Pin 1 white - 12 volt 40 amp AM1 fuseable link With all that being said there is one more thing to consider. If you get a JDM engine the engine wiring harness will be for a right hand drive car. Its going to want to have the part of the harness that goes to the ECU go through the firewall on the drivers side not near the windshield wiper motor on the passenger side so just one more problem to solve That should get you a running engine, later I'll look at some extra's that would be nice to have like hooking up the sensors in the engine to the instrument cluster.