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  1. #1
    Ultimo Miembro Fantástico Gigantesco ChrisD has much to be proud of ChrisD has much to be proud of ChrisD has much to be proud of ChrisD has much to be proud of ChrisD has much to be proud of ChrisD has much to be proud of ChrisD has much to be proud of ChrisD has much to be proud of ChrisD has much to be proud of ChrisD has much to be proud of ChrisD's Avatar
    ChrisD has been to an official Ogopogo Meet! ChrisD has donated to the forums! ChrisD helped get Luni's MR2 back on the road! ChrisD helped bring Chaos back to the Dragon ChrisD helped KM replace his 5-year-old clutch.

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    Lightbulb How-To: Re-Wire Your Swap

    The following example is an ST165 donor vehicle with an ST185 engine swap. The common assumption is that the ST165 is left-hand drive (USDM), and the ST185 is right hand drive (JDM).

    This how-to process can be applied to any Celica swap, if you consider the general principles at play. It is a step by step process which minimizes your room for error. I have used this process on 5 vehicles to date with success. However, my first swap (my personal vehicle), I did not follow this process. I used a much more difficult procedure which left me much more open to error and took much more time.

    You can expect to spend at least 20 hours wiring your swap. You may be faster with professional tools, or slower if this is your first time.

    Before you start

    Print off the following documentation, you'll be marking these up (don't ruin your own BGB's). Print in colour if you can, this will help.

    • ST165 ECU Pinout diagram: http://www.celicatech.com/bgbonline/...c/FI/FI-17.jpg
    • ST185 ECU Pinout diagram: http://www.celicatech.com/bgbonline/...c/FI/FI-28.jpg
    • ST165 TCCS diagram: http://www.celicatech.com/bgbonline/89ewd/I/54.htm
    • ST185 TCCS diagram: http://www.celicatech.com/bgbonline/...ATengcntrl.pdf

    For other diagrams, check the listing at the following link:
    http://celicatech.com/forums/showthread.php?t=81

    This thread also contains a wealth of additional knowledge regarding the swap. It is a good read.

    I'm going to use two terms here to keep things understandable:

    • Stock Harness: Your original ST165 engine wiring harness for the original car
    • Donor Harness: Your new ST185 engine wiring harness for your new engine

    Get your tools:

    • Gun-style soldering iron
    • Solder
    • Heat shrink tubing
    • Wire cutters
    • Wire stripper tool
    • Pliers with a stubby needle nose tip
    • Multimeter
    • Extra wire, 16 gauge or so (I usually pull from old harnesses)
    • Pens
    • Electrical tape, have black and another colour so that you can write on it (red works well)
    • Zip ties
    • New wire covering
    • A mask to filter out the gases is likely a wise idea

    Overall Process

    You will be 'merging' the two engine harnesses. The ST165 harness will be your "base", and you will be adding ST185 systems, one at a time (the 185 harness will be the one hacked up). You will use your pinout diagrams to tick off one wire at a time as they are completed. Yes, there are times when the ST165 and ST185 wires will be the same - however not always. This is why you check each system via the TCCS diagrams, one wire at a time. This method ensures that your ST165 body wiring does not need to be modified, including things like the fuse box.

    Get Your Workspace Ready

    1. You will need an empty room or large enough space to completely lay out two engine harnesses. A huge work bench would be great, but I've always used the floor. Your knees and joints will hate you. You'll want some sort of air circulation so that you aren't breathing in the solder fumes all day.

    2. Lay out a large tarp to keep things off of the floor.

    3. Lay out your harnesses parallel to eachother. You will want your seat close to the ECU terminals.

    Detailed Procedure

    The ECU Pinout chart will be your checklist. You will go through each wire on the ECU, one by one, converting them from the ST165 to the ST185 system.

    I will follow two examples for this procedure outline:

    Eg1: The Knock Sensor circuit (simple) and
    Eg2: AFM circuit (more complex)

    If you can follow these examples you should be able to repeat the same process for any TCCS circuit.


    1. Label your ECU connectors 1, 2, and 3 on both harnesses. (use the order they are shown on the pinout diagrams)


    2. Strip both harnesses of the wiring covering and excess electrical tape. Use a damp wrag and clean off dirt / oil as much as possible.


    3. Pick an ECU pin on the 185 harness, and find its counterpart on the 165 harness. For the most part these have the same letters, however there may be a few differences.

    Note: I usually leave the grounds (E01, E02, E1, E2, E22) and +B / +B1 for the last items to do, since there are a number of systems that tap into them. Also leave your shields (connected to ground) for last.

    Eg1: Find the KNK wires on both harnesses using the pinout diagrams. On the ST165 this is a clear wire with shielding on the bottom row of ECU plug 3. On the ST185 harness this is a white wire with shielding on the top row of ECU plug 2.

    A note on shielded wires: there are 3 circuits that use shielded wires: O2, knock, and the distributor. Shielding protects the signal from interference and outside 'noise', by encasing the wires in a metal 'shield' attached to ground. It is important that these remain shielded. If you need to extend the distributor wires (eg. JDM harnesses are shorter), ensure that the distributor wires are exactly the same length - discrepencies in length can cause issues down the road. It is possible to shield these individually, however Toyota shields the distributor wires in one casing from the factory. You should replicate this if at all possible.

    Eg2: The AFM circuit involves several wires. I suggest you tackle them all in one step, instead of trying to do each wire independently. The ST165 AFM has 6 wires, while the ST185 has 4. At the ECU, the ST165 has the FC, E, VC, VS, E2, and THA pins. The ST185 does not use the FC or E. We will look at this in detail on step 4.


    4. Find the related circuit on the TCCS diagram for both harnesses. Check for similarities.

    Eg1: The KNK circuit is identical on both harnesses. It is a single wire from the ECU to the knock sensor plug. This makes life much easier.

    Eg2: The two engines have different AFM circuits. By checking the diagrams, you can see that the ST165 has an additional wire that goes to the Circuit Opening Relay (COR), which activates a switch to allow power to go to the Fuel Pump. This feature was omitted on future revisions of the 3S-GTE. The other wires in the diagrams match up the same.


    5. Verify that the wiring is what is shown on the TCCS diagrams. There can be subtle changes on different years or models. Your diagrams may not be 100% correct. Don't assume anything.

    Eg1: On the ST165 to ST185 these circuits are identical. If your harnesses are the right length, this will be an easy wire to swap over. Note however, a JDM harness will have different lengths for wires due to the firewall pass-through on the opposite side.

    Eg2: The main issue that will catch you is wiring length on these. The ST185 and ST165 share the same wiring configuration for the AFM. Later, you will likely also want to extend the AFM wires so that the AFM can be mounted in any position you like. This will give you flex space to install a straight pipe air intake off of the turbo.


    6. Verify that the plug / connector is the same. If the same, you have the option of re-using the ST165 wire *if* you are trying to avoid extending wires. If you do not need to extend, it is probably easiest to move the wire from the donor harness to the stock harness. More to come below.

    Eg1: The knock sensor plug is identical on all 3S-GTE harnesses. This will save work in the next step.

    Eg2: The plugs are *not* the same. You will have to convert this over, or move the entire ST185 system in one piece to the ST165 harness. However, if you are going to extend the wires to install a straight intake anyways, it will save time to simply cut the ST165 wires at the plug, and cut the ST185 wires 12” from the plug to give you the additional length you require. Then solder the corresponding 4 wires up.


    7. Converting the wire(s) - you have three options depending on the circumstance.

    a) No splicing. Use this option if the length of the wire does not need to be changed, and the plugs are the same. The main benefit to this is that you do not have to splice the connection at the ECU to use the donor harness ECU plugs, saving you time.

    Carefully remove the wire from the donor harness and feed it into the stock harness. Using zip ties to ensure that the original form of the harness is kept. Set the plug where the stock plug is.

    Now remove the corresponding wire from the stock harness. Once it is out, cut it off and toss the stock harness wire in a 'spare wires' pile.

    Option a) applies to Eg1 if the wires are the same length. This would be common if your donor harness was from a left-hand drive vehicle

    Option a) does not apply to Eg1 or Eg2.

    b) Plugs are the same but new wires are too short - splice it in. Use this option if you need to extend the wire to the correct length, and the sensors have identical plugs. (most common in USDM to JDM swaps) This adds time however allows you to extend only the wires that are required. You will be soldering one connection.

    You have this problem: the donor wire is too short to extend to the plug location on the stock harness.

    Carefully remove the wire from the donor harness. Cut the wire about 12" from the ECU plug. You want it to be far enough up so that it is covered once you re-wrap the harness, but out of the engine bay if possible.

    Cut the corresponding wire on the stock harness about 10" from the ECU plug. You want a little extra length, just to be safe.

    Solder the donor wire coming from the ECU to the stock wire coming from the stock engine harness. Cover with shrink wrap.

    You will likely use option b) for Eg1, if your donor harness is from a right hand drive vehicle.

    c) Plugs are the different & wires are the wrong length - splice it in. Use this option if you need to extend the wire to the correct length, and the sensors have incompatible plugs. (most common in USDM to JDM swaps on sensors that have changed plug designs between model generations) This adds even more time however is required at times. You will be soldering two connections.

    You will likely use option c) for Eg2.

    Carefully remove the wire from the donor harness. Cut the wire about 12" from the ECU plug. You want it to be far enough up so that it is covered once you re-wrap the harness, but out of the engine bay if possible.

    Cut the corresponding wire on the stock harness about 10" from the ECU plug. You want a little extra length, just to be safe.

    Solder the donor wire coming from the ECU to the stock wire coming from the stock engine harness. Cover with shrink wrap.

    Place the donor sensor plug where it needs to be and feed it into the stock harness. Try to have the connection protected in the main loom. Make sure you don't place the sensor with too little wire. A little on the safe side (extra wire) is always best! Often times this will involve 2 to 5 wires and will be repeated for all wires on that particular circuit. (eg. AFM, distributor, MAP sensor, etc.)

    Cut the corresponding stock wire at the same location about 12" from the sensor. Solder the donor wire coming from the sensor plug to the stock wire going into the stock harness. Ensure to place heat shrink tubing to protect the connection.

    Eg2: Follow the above steps for option c) for each of the 4 wires: VC, VS, E2, and THA. You will find that VC is a common power source for most sensors. This is a 5V power source, so DO NOT splice this with a general B+ source. VS and THA are straight wires to the ECU. E2 is a sensor ground. Do not splice E2 with any other wires than other E2 grounded sensors. This is a specific sensor ground and should be kept separate to avoid ground looping (bad).

    The old FC (green) and E (white/black) wires can be cut and thrown away. These are not required on the ST185. Be careful NOT to cut E at the ECU. Track this back from the AFM plug to the furthest point back where it splices into the main harness.

    Step 7 is now done.

    No matter which option (a, b, c), you now have a wire connected to from the donor harness ECU plug that feeds through the stock wiring harness. One by one, you will repeat this process until all donor harness ECU wires are incorporated into the stock wiring harness.

    Note: some wires do not go into the "engine" per se. Some feed into the body harness or into the circuit opening relay. The same process applies however - you want to make sure the COR and body harness receive the same signals that it used to receive with the stock harness.


    8. Use some coloured electrical tape to mark the sensor plug. IE- write down the name on the electrical tape and affix it to the plug. You will speed up your install if you know which plugs go to which wires.


    9. Cross off the pin on both your stock and donor ECU pinout diagrams. This is your checklist and will help you keep an eye on your progress.


    10. Repeat steps 3-9 for every pin on the diagrams.

    You may find that some systems are not included one or the other harness. EGR system is a typical example. If you do not require the EGR, pull it out of the stock harness as the new ECU will not use it if it is Jap spec. Another common example is the O2 sensor heater - HT. It is not required as a single wire O2 sensor will suffice. However, fuel mileage on cold start may be better with it installed. I live in chilly Canada and don't use it, and have been just fine. One more example is the catalytic converter heat sensor. JDM cars use this, USDM cars don't. It is not required - cut it loose.

    You may also find that pin naming convention may differ. (the ISC valve is a good example - ISC1 = RSC and ISC2 = RSO) You will have to check the wiring diagram to confirm which wires are which.

    Also, you may find that some systems have different wires. The A/C system is a good example. For this specific swap, ensure that the A/C is mated to AC1. ACT is for the A/C amplifyer and is not required as the ST165 has a seperate A/C control unit.


    11. Deal with the grounds (E01, E02, E1, E2, E22), +B / +B1, and shielded wires.

    These are generally fairly simple to identify once you are at the end. For the most part, you can simply do the splices at the ECU. The stock harness will have sufficient grounds and appropriate +B connections to the body where required.

    Grounds can be brown, black, or white/black. Make sure to double check what you are connecting before doing these!

    +B's are usually black / orange. The stock harness will use this a fair bit and include many splices throughout the engine. For this reason it is best to use the +B wires from the stock harness.

    Connect the shields (exposed wires coming from shielded wires) like they were on the previous harness - usually connected to a ground somewhere near the ECU plug.


    12. Now that every single pin is crossed off on your pinout diagrams, check everything. Physically check the pins to make sure that they go to the correct plugs and follow the wiring diagrams accordingly. Best to check now while everything is exposed. Use a multimeter to ensure connectivity and physically follow the wires where possible.

    The donor harness should be completely disconnected now from the stock harness. If not, find out which wires are still connected and determine if they are required.

    The stock harness ECU plugs should be completely disconnected from the wiring harness. If not, address the wires that are still connected. They should not be.


    13. Wrap it up with new and clean wire cover. Use electrical tape to seal it up nicely. Take your time and ensure that everything fits together like it should. Attach the cover at the intake manifold area, and the cover over the valve cover.


    That's about it, you're done. Now go install it on your engine and enjoy!
    Last edited by ChrisD; 07-20-2011 at 07:48 PM.
    1988 ST165 2.2L @ 370awhp
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    1994 ST205 WRC
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  2. #2
    Lifetime Member shreddr69 is on a distinguished road
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    Sorry but the wiring schematics aren't loading. It comes up with a "not found" message. Any ideas? Thanks....

  3. #3
    Ultimo Miembro Fantástico Gigantesco ChrisD has much to be proud of ChrisD has much to be proud of ChrisD has much to be proud of ChrisD has much to be proud of ChrisD has much to be proud of ChrisD has much to be proud of ChrisD has much to be proud of ChrisD has much to be proud of ChrisD has much to be proud of ChrisD has much to be proud of ChrisD's Avatar
    ChrisD has been to an official Ogopogo Meet! ChrisD has donated to the forums! ChrisD helped get Luni's MR2 back on the road! ChrisD helped bring Chaos back to the Dragon ChrisD helped KM replace his 5-year-old clutch.

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    Fixed.
    1988 ST165 2.2L @ 370awhp
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    1994 ST205 WRC
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