This page contains information on the installation of an Autronic SMC programmable Engine Management System into a 1990 Toyota Celica GT-Four (ST185)

The installation can be broken down into two main sections. One is the modifications that are carried out to accommodate the physical installation of the unit, relative actuators and sensors, and removal of stock parts no longer required, which will come under the category of Preparation. The other is the rewiring of the stock engine wiring harness to accommodate the Autronic, which will come under the category of Rewiring. You can click on any of the smaller images on this page to view them larger. My advise is to read this write up first and then proceed, this will help to save you from wasting your time putting back on something, that you realize later should have been left off, when you reach another section.

Preparation

The first stage is to decide where you are going to mount the Autronic SMC ECU. I chose to mount it in the same location as the stock ECU.

Removal Of The Stock ECU & Fabricating A New Mounting Plate

Before beginning this installation disconnect the negative cable from the battery. The ECU is located behind the centre console on the flooring. Simply peel back the carpet and you will see that it is secured by two nuts on the left hand side, and one on the right hand side. On the left hand side you will see three connectors plugged into the ECU, and another connector plugged into the "circuit opening relay" (located on ECU). Unplug all these connectors, then remove the three nuts securing the ECU in place, and then remove the ECU from the left hand side. It's tight under there so some shifting to different angles while removing may be required. You are now ready to use the stock ECU for a reference to make a mounting plate to secure the SMC. You will also need (unless you want to fabricate your own) to remove the three brackets that are attached to the stock ECU, so you can use them on the new mounting plate you are going to make. Using the pictures in this section as a guide, you should easily be able to figure out how to go about fabricating your new mounting plate. Once the Mounting plate is finished, and the SMC ECU is attached, there are two more things to add to it, the main relay and the reluctor interface (refer to the "Package" section for info on the reluctor interface). To attach the reluctor interface use the bracket for the circuit opening relay that was attached to the stock ECU. Using two cable ties, attach the reluctor interface to the bracket, and then bolt the bracket to the left rear screw that attaches the SMC to the mounting plate (refer to the larger picture for clarification, if you need it). The next thing to attach is the SMC's main relay. To do this I made a bracket (refer to the larger picture), and attached it to the left front screw that attaches the SMC to the mounting plate. The final step is to remove the protective plastic piece that is on top of the stock ECU, and put it on top of the SMC ECU, You will want the protective piece to overhang at the front, so it protects the connector as well. Click here to see a picture of the SMC ECU installed.

Removing Parts No Longer Required

A few stock parts will not be needed by the Autronic. They are as follows, the Air Flow Meter, the Turbo Pressure Sensor (MAP), the Injector Resistor Pack, the Fuel Pump Resistor, the Idle Speed Control Valve, and the Cold Start Injector.

Air Flow Meter: The Autronic SMC is a speed density system and as such uses as it's main input, manifold pressure, air temperature and engine speed (rpm) to determine fuelling and ignition requirements, which makes the Air Flow Meter (referred to from here on as the AFM) obsolete. Removal of the AFM is very straight forward, so there is no need to go into any great detail. What you will need to do is add a performance air filter with a 3 inch opening. The way I did mine, was to use a short length of 3 inch pipe, and attached the filter to one side, and then attached the stock intake hose to the other side. You will have to get the side of the pipe you are attaching to the stock intake hose flared a bit, as the hoses inner diameter is slightly more than 3 inches. To get an idea of what I did, click here to view a picture of my engine bay.

Turbo Pressure Sensor: The Turbo Pressure Sensor (referred to from here on as the MAP sensor), isn't needed by the SMC, but it is needed for the stock boost gauge in the instrument cluster. If you don't care about the stock gauge, you can simply remove the sensor (the gauge will read full boost all the time). If you want the gauge to work, you will have to find a 5v DC supply for the sensor. This wasn't a problem for me, as the ERL System2 water injection comes with a 5v DC supply for a MAP sensor. Another possible way is to tap into the supply from the SMC wiring harness, for the Throttle Position Sensor, however, I strongly recommend that you check with the dealer you purchased your Autronic from, before attempting to use that feed.

Injector Resistor Pack & Fuel Pump Resistor: The injectors in the ST185 are low impedance, and the stock ECU uses saturated drivers, which requires that the 12v DC feed for the injectors must run through a resistor pack. The SMC ECU uses the better peak and hold type drivers, which can control the low impedance injectors, without the use of a resistor pack. The pack is located just under the battery behind the radiator. You will need to remove the battery in order to gain access to the bolt, to remove the pack. Note that there is also another resistor on the same bracket as the injector pack. This is the fuel pump resistor, and was used by the stock ECU to reduce voltage to the fuel pump for low load driving conditions. This too, is no longer required. This part is dependant on whether you wish to join the wire from the Autronic main relay straight to the pump, or use the existing stock wiring. I used the stock wiring as it is the right gauge, and was the easiest method. In order to bypass the fuel pump relay, you will need to locate the relay box next to the alternator, and remove the fuel pump relay (the only yellow relay). You now have to bridge two of the four vacant terminals. If you are standing facing the car, jumper the top left terminal with the bottom right terminal. This set-up allows you to connect the wire for the fuel pump from the SMC main relay, to the blue wire with the orange stripe, that is located in the connector that was plugged into the circuit opening relay.

Idle Speed Control Valve: The Autronic does not control stepping motor type Idle Speed Valves (referred to from here on as the ISC) , which as such makes the ISC obsolete. Some of you are probably thinking that idle quality will be bad without this, but this is not the case. The Autronic has an "Idle Ignition Table" that supplies a very stable idle. My car idles between 950 rpm and 1050 rpm, but quite smoothly. It is actually just as smooth as when it had in the stock ECU. To remove the ISC you will need to remove the intercooler, and then remove the throttle body. To remove the throttle body, you must first remove a bracket that supports the throttle body. The bracket has two 10mm bolts attaching it to the cylinder head, and two 12mm bolts attaching it to the throttle body. Then remove all hoses, the ISC connector, the Throttle Position Sensor connector, and the accelerator cable from the throttle body. There are four 12mm bolts holding the throttle body to the plenum chamber, remove these, and remove the throttle body. You are now ready to remove the ISC. The ISC is held onto the bottom of the throttle body with four screws. These screws will be in tight, so use the proper size screwdriver. I prefer to use a ratchet that I have, that comes with various screwdriver bits. A ratchet allows you to use more down force, and gain better leverage, so avoiding the probability of stripping the head of the screw.

At this stage you have the ISC disconnected, and are ready to build a blanking plate for the bottom of the throttle body. I used aluminium to build a plate. Use the ISC valve to mark out the outline (it is not necessary for it to follow the same shape, it can just be rectangular), and positions of the four holes on the aluminium. Then cut the blanking plate out of the aluminium, using a hack saw, or some type of saw. I don't recommend snips for this, as they tend to make the aluminium curl, and you want the blanking plate to be flat. Once the plate is cut out, drill your four holes, and file away any imperfections. If you are like me you can then proceed to bring the plate to a nice shiny finish. Start by using 400 sandpaper, and work your way up to 2000 sandpaper, and then polish with Brasso. The final step is to secure your blanking plate to the throttle body. You will need to source shorter screws, as the stock screws are too long.

Another thing I removed was the piping (one piece, see picture) for the ISC valve, coolant hoses, vacuum supply for power steering pump, and A/C idle up VSV. This is not the easiest part to remove, reaching the bolts holding it on is hard enough, but working it out from between the intake manifold and the stays, requires lot's of manoeuvring. You really don't need the coolant hoses that lead to the ISC. These only serve to keep the throttle body warm, which you really don't want on a turbo car. When you remove the piping you will be left with two open coolant lines (that used to run to the throttle body), so attach a hose from one end to the next, or you could blank them off. For the power steering valve, I ran a hose straight from the valve to the connection point on the back of the plenum chamber, and the other hose I ran along the intake manifold stays, to my source of pre turbo air. You need to source pre turbo air for the A/C and power steering valve, so run a hose from the stock location on the first intake hose (Hose nearer the air filter), and connect it to them using a "Y". You will also find that the pipe attached to the bracket by the distributor (the bracket with the clips for the spark plug wires), is not need anymore.

Cold Start Injector: I never bothered to enquire whether the Autronic could control the Cold Start Injector (referred to from here on as the CSI), because I feel it is not necessary. The Autronic has "Post-start Enrichment Multiplier", and "Post-start Enrichment Time-out" maps, as well "Warm-up Enrichment Multiplier" and "Warm-up Accel. Enrichment Mutilplier" maps, so all your needs for cold start fuel are covered.

The first thing you need to do is remove the fuel line going from the fuel rail to the CSI. This is a banjo connection on both points, and the banjo is held with a 10mm bolt. Remove the line from the fuel rail and the CSI. The CSI is held in place in the plenum chamber with two bolts, simply remove these two bolts, and remove it. The next step is to build a blanking plate similar to the one you made for the throttle body. You can use the CSI gasket for a template. When you have finished your blanking plate, attach it to the plenum chamber (you can re-use the old gasket, as it is a metal gasket and should seal back fine). You will also have to blank of the opening in the fuel rail. To do this I used a spacer with two perfectly flat sides (the same thickness as the banjo), two new copper gaskets, one on either side, and used the original bolt to secure it to the fuel rail.

Parts That Must Be Added For The Autronic

There are only three main things that have to be added, the Air Temperature sensor, the Boost Control Valve (referred to from here on as the BCV), and the stock ignitor must be replaced with a Bosch Ignition Module. The only other things that have to be added is relays, depending on what features you use. I used the "Fan Control" to control the radiator fan, the "On/Off" map to control the T-VIS, and the "Fan 2" to control a cold start valve to supply extra air to the engine when it is cold. The last one is achieved by using the 87a terminal of a relay. I set the "Fan 2" to come on at 45 degrees Celsius, and turn back off at 10 degrees Celsius (a temperature the coolant would never drop back to). When the vehicle is started and the temperature is below 45 degrees Celsius, the relay is off, and the terminals 30 and 87a are bridged, which results in power to the valve, thus supplying extra air. At 45 degrees Celsius, the relay is switched on, and terminals 87 (which has nothing attached to it) and 30 are bridged, which sends 87a open circuit, and the valve turns off.

The BCV can be installed anywhere. I chose to install it on the bracket that supports the air filter. This location is relatively close to the wastegate hose connection and the turbo hose connection. The Bosch ignition module was located in the same place as the stock ignitor. Remove the stock ignitor by removing the bracket from the firewall, which is held by two 10mm bolts. Remove the ignitor from the bracket, by removing the two screws securing it to the bracket. The Bosch module requires a heat sink, so I used a piece of aluminium, and then drilled the holes in the aluminium, and the stock bracket, for the Bosch module to attach to them. The Bosch Module will come with a white silicone grease on the bottom of the unit, do NOT remove this grease. Click here to view a picture of the engine bay, where you will be able to see the Bosch Ignition Module.

The Air Temperature sensor (referred to from here on as the air temp sensor), is probably the most involved addition, and will require a machine shop to make a fitting for it. The sensor will need to be mounted in a position in the plenum chamber. The intake manifold has two plugs either side of it, so I decided to use the location for the plug on the left hand side of the manifold. In order to use this space the plug must be removed from the manifold. Removal should be done when the engine is cold. You will need a large screw driver or something similar with the flat end almost the same thickness as the lip on the plug. Place the screwdriver on one particular spot, I chose the top, and using a hammer, start to hit the screwdriver forcing the top to go inwards. It helps to move the screwdriver a little to the left and give it some hits, and then a little to the right, and give it some hits, then back to the middle, but don't go to far left and right, you want to keep your efforts concentrated on the top of the plug. What will happen is that eventually the plug will start to shift on it's axis. It's like taking a quarter between your fingers, and holding opposite edges, and tilting it. When the plug tilts far enough you can use a pliers to pry it out. Try and not damage the plug too much. The edges will get pretty badly messed up from the pounding, but don't worry about that.

Take the plug and air temp sensor to a machine shop, and get them to make you a piece from billet aluminium, thick enough for the threads of the sensor, that is slightly, and I mean very, very, slightly larger in diameter than the stock plug. Then get them to tap a hole in the new plug, for the sensor. The sensor's thread is tapered, and as such the machine shop that made mine, created a very nice concave design on the inside of the plug, so that when the sensor was screwed in, the very edge of the threads was flat with the concave, and the sensor part protruded nicely out. It is also important that the new plug have a tapered inside edge just like the stock plug. When you get home place the new billet aluminium plug in the freezer, and leave it there for several hours. Get everything you are going to need ready, like hammer, a socket that will fit nicely on top of the new plug (so as not to damage the threads), and some thread locker. Spread some thread locker around the inside of  the hole in the intake for the plug, then retrieve the new billet piece from the freezer, and start to push it into the hole. It should go in about half way, if it looks way to big, do not start, return to the machine shop, and ask them to decrease the diameter slightly. If it goes in rather good, about half way, just past the taper, then place the socket over it, and hit the socket with a hammer to force it into the hole in the plenum. Hit a few times and check all the edges. If it is protruding more on side, then concentrate your hammer hits on that side, then check again, and repeat this process, until it is flat with the intake manifold. Put a little teflon tape on the threads of the temp sensor, and screw it into the new plug. Don't install it to tight, as aluminium is soft and you could strip the threads. It should be just tight enough that you can't unscrew it by hand.

Rewiring

Deciding on How To Approach The Rewiring

There are two choices when it comes to the rewiring. You can cut the wires at the location of the stock ECU, and then solder the wires for the Autronic harness to the relevant stock wires, and then do variuos ccorrections to the harness in the engine bay. I did not choose this approach, as I feel it is too much of short cut, not to mention it would make trying to figure out how certain wires were connected in the stock harness, very difficult. The other choice is to rebuild the stock harness. I went this route for a couple reasons. The first being the ability to actually trace where wires were going, and which wires connected back up to which wires, and the second being that it would replace most of the older stock wiring harness wires.

Removing The Harness

Go back to the location where the stock ECU used to be located, and you will notice two large connectors, a white one, and a grey one, disconnect them. There will also be a clip holding the stock wiring along the flooring on the left hand side. If you look towards the top of the clip, you will see it is attached to the protrusion of a stud. At this location on the clip, you will notice a little tab. Rotate the tab about 90 degrees, and then pull the clip off. This will make the harness inside the vehicle ready for removal. Your next step is to remove the harness from the engine bay. Start on the alternator side of the engine bay. Remove the following connectors, as well as remove the connectors from any clips or brackets. The CAT temperature sensor, the radiator fan switch, the A/C compressor, the oxygen sensor, and the alternator connectors. Under the alternator, you will find a 10mm bolt holding the harness, remove it. You will also find a 12mm bolt on the side of the alternator bracket holding the harness in place, remove this as well. In order to get the harness out from this location, you will need to remove the alternator/AC compressor belt. Once the belt is out of the way, you can remove the harness from it's location by the alternator. The next section of the harness is held in place near the right hand side of the valve cover, by two tabs that simply slip over the protruding ends of the bolts that hold the timing cover in place. You are now ready to deal with the area by the fuel rail.

The harness is housed in a plastic piece between the fuel rail and intake manifold. Before physically removing it, some connectors have to be disconnected. The most difficult ones are the Turbo VSV (if you are still using it), the T-VIS VSV, the knock sensor, and the ground strap. All of these are located under the intake manifold, and access from the top of the engine is impossible. Jack up the front right hand side of the car, place a jack stand under the vehicle, and remove the wheel. You will have to put your hand through the opening for the steering rod ends, and feel your way around until you find the knock sensor connector, the T-VIS connector, and the ground strap (which will be held to the manifold by a 10mm bolt), then disconnect them. The Turbo VSV is probably easier reached by approaching it from the left hand side of the engine bay through the top. Once located disconnect it. Next disconnect the distributor connector, and the speed sensor connector. This clears the area under and around the intake manifold of all connections, so go ahead and remove the connectors for the injectors. The cold start injector, ISC valve, and throttle position sensor connections will be already disconnected, since you removed the throttle body earlier. Remove the 10mm bolts holding on the brackets attached to plastic piece housing the wiring, remove the fuel pressure regulator, and remove the oil cap (I usually place a piece of cloth in the hole to stop anything large falling in the hole for the oil cap). You will now have enough room to remove this section of the wiring harness. Some manoeuvring will be required to get the plastic piece out from between the intake manifold and fuel rail.

In order to remove the harness completely, there are more things that have to removed and disconnected. Let's start with the disconnections first. Disconnect the turbo pressure sensor connector, the ignition coil connector, the ignitor connector, the three way pressure switch connector (located near the diagnostic box on A/C line) and the two connectors near the diagnostic box, as well as removing the diagnostic box itself from the bracket it is located on. There will be a rubber boot bolted onto the firewall  where the engine wiring harness comes out, it is held in place by two 10mm nuts, remove them. On the left hand side strut tower, you will see a clip that holds the harness to a bracket. Pry the tab on this clip and slip it off the bracket. Near this same location, below the wiring harness, you will see a connector with two wires, disconnect it. At the end of this bracket you will see another clip on the wiring harness, do the same for this clip. Unplug the reverse light switch connector (located on top of gearbox), the large connector for the oil pressure switch, coolant temperature sensor, and cold start injector time switch, the connector for the coolant temperature sensor (for the gauge in dashboard, single wire), and the coolant temperature sensor (for fan control with A/C on, single wire). The connectors for the fuel injector resistor pack and fuel resistor pack (the later is not part of the engine wiring harness) will have already been disconnected. Disconnect the connectors for the starting motor. There is another plastic piece that is attached to a bracket on the gearbox, that has to be removed. One on side (side closest to engine) it will have a clip with a tab, pry up the tab and remove. The other side will have a circular tab that pushes through a circle hole in the bracket. The tab has a protrusion top and bottom that must be pushed together, in order to push it out of the bracket. Next you will now need to remove the hose from the fuel filter, and the two coolant hoses leading to the heater core.

Your next task will be to open up the bottom of the main fuse/relay box (located next to battery). The battery should have already been removed to gain access to the resistor pack's bolt, so you will have more than enough space. Remove the top cover, then remove the bottom cover. This box will be fairly brittle from age, so expect some tabs to break, and be aware that you may have to find a way to hold the bottom on, should most of the tabs break. The section with the four main fuses, slides out from the bottom of the box. There is a tab on either side that must be pushed to allow the fuse section to slid out. Once this is out, take note of which connectors on the bottom of the box are from the engine wiring harness, and remove them. The battery positive terminal should already be off, as the battery would have been removed. The last connection is a round single wire connector, that is down on the flooring where the battery would sit, disconnect it.

Lift the harness out of it's position, and get it to a point where you can start to pull the harness section that inside the car, out from the hole in the firewall. Once everything is clear, lift the entire harness out of the car. When the harness is out, lay it on a large space such as the floor, and spread it out similar to how it is in the picture. The next phase is to make sure you have a reference for getting the lengths of the wires you will be adding, and the length and angle of the different points where wires will branch off. The easiest way, is to have a spare harness, to use as a guide. The other way is to photograph the harness, scan the photo and print it. Then take all the measurements from the harness, like length from harness to connector, length from one branch to another, etc., and note them on the print out.

Disassembling The Harness

Now it's time to disassemble the harness. You only need to disassemble from the ECU connectors to the plastic piece that holds the wires for the injectors, etc. The piece that goes over the valve cover and beyond, does not have to be disassembled. Also the rubber boot that attaches to the firewall should not be removed, or moved from it's location. This is a tedious process, and be assured that you will probably be able to lift a 5lb weight without closing your fist, your hands will be that sticky when you are finished. To be on the cautious side you could place the parts, tubing, clips, etc., from the wiring harness in the order they were in, on the floor. I didn't bother with this, as this was the second time I rebuilt a GT_Four harness, so I was familiar with where they came from and the order.

Rewiring The Harness

There are a few things that need to be covered before you begin rewiring the harness. One is the tools and supplies you will need. I have listed as complete a list of tools as I can think of, however you may find you need something that may not be on the list. One thing not mentioned that you should definitely have is wiring diagrams for the car. The Chilton's manual is for U.S. cars, but the wring diagrams are adequate. Needless to say the Toyota Workshop manual will work.

Soldering iron	60/40 flux solder	Heat shrink tubing
Electrical tape	Wire stripper	Wire cutters
Exacto knife	Multi-meter	Set of small screw drivers
Crimping tool for connectors	Can of Electrical cleaner	600 sand paper

Soldering: If you are not familiar with soldering, I suggest you practice on some pieces of wire before actually soldering connections on the harness. The main thing you want to avoid is a cold joint. A cold joint is formed when the wire itself has not reach a high enough temperature or the wire is contaminated, and the solder has not spread between it. Cold joints generally tend to look very dull. The proper technique for soldering is to melt a very small portion of solder on the soldering iron tip, place the tip of the soldering iron on the wire you are going to solder, and leave it there for a few seconds. This will heat the wire up. Then position the solder between the iron and the wire, and the solder should immediately start to spread along the wire easily. The finish will usually range from looking clean to very shiny. Another problem is corrosion or contaminants on the wire. The flux in the solder will take care of mild contaminants, but in something like the harness, you really want to ensure a good joint. I usually flatten the wire and lightly pass it between 600 sandpaper, then flatten from a different angle and repeat. Then I spray a healthy dose of electrical cleaner on the wire, as preperation for soldering.

Solder Joints: The first stage is to strip the ends of the two wires you are going to solder. Then cut the needed length of the correct thickness heat shrink tubing, and slide it onto one of the wires. Slide it as far away from the point where you will be soldering. If it is too close, it may start to shrink from the heat of the soldering process. Next twist the two wires together neatly, and proceed to solder them. Slip the heat shrink tubing over the joint, and using a heat gun, or a cigarette lighter, heat the tubing, until it shrinks to nice tight fit, taking up all the contours of the solder joint. The next stage isn't really necessary, but I like overkill in situations like this. Cover the heat shrink tubing with electrical tape. I also try to make sure all my solder joints are in the main section of the harness, where they will not be exposed to bending and flexing, like would be expected close to the connector.

Getting Started

You should now have a nicely laid out, stripped stock wiring harness laying on the floor. You will need to prepare the Autronic SMC harness. To do this remove the black sleeve that comes with it, and remove all the cable ties that are attached, except the one for the main relay connector. Place the SMC connector near the stock ECU connectors (give yourself about 3 extra inches of length from the stock ECU connectors), and position all the wires from the Autronic harness in the opposite direction of the stock harness.

The Actual Rewiring

I use a process that makes the job simple. I decide on a connection and then remove that wire from the stock harness, and then add the relevant wire from the Autronic harness to the stock harness. For example, you want to connect the negative wire for cylinder 1 injector from the Autronic harness, so you cut the stock wire for cylinder 1 injector at the point you desire the joint to be, and remove it from the harness, and then remove it from the ECU connector (there is a clip that can be pryed with a small screwdriver to pull the wire out of the stock ECU connectors). You then hold the wire from the Autronic harness for cylinder 1 injector about 3 inches away from the Autronic connector, and using the old wire, determine the length of wire required, adding about an inch and a half extra for the joint, and cut the wire, then make the joint. Before you can finish the harness, you have to complete the installation of all the things you are using, and that must be used, so you can determine the correct length of the wires to reach them. The wiring diagram found further down the page, should make it easier for you to figure out the correct connections. One thing worth noting, is that in order to keep the stock tachometer and A/C working, you will need to install a 1 Kohm resistor (10% tolerance) between the negative side of the coil, and the wire leading to them.

Pictures Of the Completed Wiring Harness