AEM EMS V2 Install on my MKIV Supra

I decided to use AEM v2 on my car because I was already familiar with it. I've used it in my 3000GT VR-4 without any issues for the past 7-8 years. There are several sensors that need to be installed in addition to the plug-n-play ECU. This is going to document the where, how, and why for each one. I'm also going to cover how I hot wired my 2 OEM Supra fuel pumps. If you don't feel like reading I also posted a 30 minute video on YouTube regarding it.

The wiring diagram I reference in my video is from the factory service manual. I found it online here: http://shoarmateam.nl/upload/MKIVSupra/Supra-MKIV-Repair-Manual/Wiring%20Diagrams.pdf Assuming you have the turbo model just print out pages 246 and 247. You can cut the top header off one of the pages, then tape the diagram together.

The IAT and MAP sensor will come with pigtails that you need to crimp together. To do this correctly you'll need a MOLEX crimp tool. The original tool is a MOLEX brand, part# 63811-1000. It's around $60. There are cheaper alternatives. Any wiring that you splice into I'd recommend soldering and heat shrink tube.

AEM IAT Sensor (Part# 30-2010)

The first sensor is the IAT (Intake Air Temperature) sensor. It measures the temperature of the air going into the engine. Speed Density needs this to help make it's air fuel calculations. Some people will mount the sensor in the air intake feeding the turbo. Some people (including myself) like to mount them pre-throttle body because we feel like it will provide a more accurate temperature reading (intercooler will cool the air). I gave myself some room before the throttle body just incase I ever want to run meth. The sensor comes with a 3/8 aluminum NPT bung. I had to buy a stainless one for my pipe.

Wiring is very simple for this sensor. There are 2 wires that need to connect to pins B65 and B45 of the ECU. You don't need to run the wire all the way to the ECU. These pin locations already feed out to the OEM MAF sensor pigtail. So you can tie into the MAF pigtail. Connect 1 wire off the IAT sensor to the pink with blue stripe wire on the MAF connector. Connect the other IAT wire to the brown with black stripe wire on the MAF connector.). It doesn't matter which IAT wire goes where. Direction doesn't matter for this sensor.

Map Sensor (Part# 30-2130-50 or 30-2130-75)

The other sensor Speed Density needs is the MAP sensor. It measures Intake Manifold Pressure. AEM sells several different sensors. I'd recommend the part numbers I listed in the header. 30-2130-50 is the 3.5 BAR sensor and 30-2130-75 is the 5.0 BAR sensor. The difference is how much boost they can read. A BAR is 14.7PSI. With these sensors the first BAR is used for vacuum. So 3.5 BAR sensor is more like 2.5 BAR or ~37PSI. A 5.0 BAR sensor is more like ~60PSI. Both sensors are the same price. I would get the smallest one that will work with the boost you are going to run. These are 0-5V sensors. If you get a 5.0 BAR sensor and only run 30PSI of boost, you'll only be utilizing the lower half of the scale. Running the 3.5 BAR sensor will take advantage of the full scale and give you more precise readings.

The thread on this sensor is 1/8 NPT. The Supra has a factory MAP sensor that works up to 18PSI. Chances are that won't be sufficient. The OEM sensor can be removed from the intake manifold. The existing nipple can be removed and the hole can be tapped out to 1/8 NPT. If you are careful you can do it with the manifold still on the car. Just remove the throttle body and shove a strip of cardboard into the intake manifold to block off the runners. There is a 3" ledge on the left side of the manifold that all the shavings will drop onto. You can vacuum them up.

Some people will say mounting the MAP sensor directly to the manifold is bad because of Vibrations. Personally I've never had an issue with it. Even the OEM Map sensor was mounted directly to it. Alternatively you could put the sensor elsewhere and run a vacuum hose to it. Doing this means you'll have to extend the wiring some.

There are 3 wires for the AEM map sensor. Fortunately they are the same 3 wires that ran to the OEM map sensor. Unlike the IAT sensor, they must be hooked up a certain way. Cut the OEM connector off and re-pin the 4 wires to the AEM connector using the MOLEX tool.

Boost Control Solenoid MAC Sensor (Part# 30-2400 or MAC 35A-AAA-DDBA-1BA)

This is used to control boost. It installs just like a boost controller. The solenoid is made by MAC. AEM just puts their own sticker on the sensor and charges $50 more. There are 2 wires coming out of this sensor. Direction does not matter. One wire needs to see +12V switched, and the other wire needs to feed into the ECU (pin 60B). Fortunately there is a pigtail in the engine bay that has everything you need. The blue VSV connector that is located near the Alternator connector is what you are looking for. Cut off the connector and then feed the Blue with White Stripe wire and the Black with Red Stripe wire to the 2 wires on the MAC valve. Again it doesn't matter which wire goes where. Be careful routing the wire through the engine bay. Try and keep it away from the turbo exhaust housing.

Wideband O2 Sensor

AEM sells a few different wideband gauges that can all output a 0-5V signal that the AEM EMS v2 ECU looks for. I chose not to buy their gauge. Instead I bought their controller (Part# 30-0310). So the ECU will know the a/f ratio, but I won't unless I have my laptop hooked up. I opted for this because I plan to buy a BTI gauge which will interface to the ECU and it will be able to show me multiple parameters aside from just the a/f ratio. This way my car can have a single gauge that shows me everything.

The wideband o2 sensor itself will come with a stainless bung. Chances are it won't be needed because just about every aftermarket downpipe already accommodates one. If you still have a stock front and/or rear o2 sensor they can be removed and blocked off. AEM will not need them to run. Instead it will use the wideband for O2 feedback both when the ECU is in closed or open loop.

Typically their wideband gauges will need power (switched +12V) and ground. They also will have multiple output wires. You want to connect the 0-5V output wire to ECU B47. You could probably do this all under the hook and tie into the stock front o2 sensor connector. I chose to run the wiring inside the car and tap into the ECU directly. This way I have less wiring to try and hide in the engine bay. For ground I used a 10mm bolt over on the passenger foot well. For power I used a fuse pigtail coming out of the Seat Heater fuse spot in the drivers foot well. I think the OEM Seat Heater were only an option overseats, but the fuse spot is present on USDM cars.

Fuel Pump Hotwire

My car is running the Powerhouse Racing Stage 1 fuel kit. This means it is running 2 OEM fuel pumps on the stock fuel pump assembly. A hole gets drilled into the top of the assembly and an AN fitting gets added. One fuel pump will utilize the stock fuel line, and the other will utilize the aftermarket AN line. With AEM you can hotwire the fuel pumps and use the ECU to prime them for two seconds when the ignition is on. The stock fuel pump controller that was in my hatch has been removed.

The first thing to do is choose the correct wire size. To do this we need to know how much current the pump will draw. A Supra fuel pump will draw 15.5 Amps at base fuel pressure (usually 43.7PSI) according to this article. I know I plan on running 30psi of boost. My fuel pressure regulator is going to see this. This means under full boost I could need ~75psi of fuel pressure. According to this article that is 17 Amps. It technically could be a little more if I exceeded 30PSI or if my alternator output more than 13.5 Amps. So I like to add 2 Amps to play it safe. This means I could see 38 Amps with both of my fuel pumps.

Now that I know my current draw I can figure out the wire size needed to run from the front of my car to the back. It's about 12'. There are several charts online that recommend 6-8 gauge wire. I went with 4 just because that is what my AMP uses and I found a nice Kicker fuse distribution block that took 0/1 gauge in and had two 4 gauge outputs. I also used Oxygen Free Copper (OFC) wire. It's quality wire and not that cheap aluminum or CCA wire. If you do some research online you'll find some videos that show how much better an Amp performs using OFC wire. It ends up making more power and the wire runs cooler.

So going from my battery I have 0/1 gauge wire that goes to my Kicker fuse distribution block that is just a few feet away. From there I have two 4 gauge outputs. One runs to the amp under my passenger seat. The other runs to my hatch where I'm using a Tyco 75A relay (Part# V23232-D0001-X001) to power my fuel pumps. The output of the relay is also 4 gauge wire that I split into two 8 gauge wires. Each 8 gauge wire ties into the factory fuel pump harness. One goes to the existing fuel pump power wire. The other goes to the existing fuel pump ground wire which has been repurposed to be a power wire for the second fuel pump. For a ground I have a 8mm stud that was added to the top of my fuel pump assembly and I've got a ground wire bolted to it.

Now to get the relay to trigger, I'm using the Blue with Red stripe wire that went to the OEM fuel pump controller as a power wire to the relay coil. When the other side of the relay coil gets grounded it will activate the relay. I ran a wire to the ECU and used pin B72 which is a low side output so that I can control when he relay coil sees ground. The AEM manual that is delivered with the ECU will recommend using pin 68B. However I found that there was no wire going into that ECU connector and it looked difficult to try and add one. So instead I used 72B which was a low side output used for the rear o2 sensor. Since that sensor is not longer needed, it's fine to repurpose it.

ECU Mount

I bought an ECU mount (you can see it in the video link above) from a seller on the SupraForums (Flintstonekid). It worked but I wasn't happy with the design. Technically it worked, but I felt that it left a pretty big gap around the sides of it. The carpet didn't really mold around it well. I'm sure if the passenger pushed their foot to the left of the ECU they'd discover a big hollow spot, or even worse tear the carpet. Seeing as I have new carpet I didn't want to risk it. I thought about adding some thick foam to the left and right of the ecu, but decided to try making my own instead.

This is what I came up with. I made my template using paper, then made my proof of concept design using some peg board material and wooden spacers. Once I knew it would work I ordered aluminum. I have about $90 in material into it (2 3/16" sheets of 24x12 6061 aluminum, and a 12" long 1" diamter aluminum dowel). After some careful cutting, drilling, tapping, and welding I have something that fits and works well. The ecu is protected and the passenger has a sturdy area to rest their feet. The carpet also transitions to it perfectly with no large gaps behind it.

I added some notes to the back of the cover. I don't plan on ever selling my Supra, but just in case something happens to me the next owner will appreciate it.

BTI Gauge

I has a few people ask me about the BTI gauge wiring, so I'm adding this section. The BTI gauge has 4 wires coming out of it. White goes to CAN1H (Pin 12A on ecu). Green goes to CAN1L (Pin 11A on ecu). Red goes to switched +12 volts. I forget what wire I used, but on the factory traction control connector there is one I tied into. Most likely black with a white stripe, but test yourself with a multimeter or test light first. Then ground I connected to the same bolt I used for the wideband gauge. The the two ecu connections I cut the oem wiring about 6" after the pigtail and tied in that way. If you look carefully two pictures up at the green and white wires, you will see what I mean.

Hopefully this helps other people. I had to do some digging to piece together all this information myself. I tried to make the install as clean as possible. I also made a quick video showing it from all angles and go over measurements... Just in case anyone else wants to make one.