EMS series 1 closed loop fuel controller | AEM
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Last seen: 2 years 1 month ago
Joined: 06/06/2018 - 11:49
EMS series 1 closed loop fuel controller

Hey guys, 

I hope you can help me. The Supra of a friend of mine is equipped with a series 1 AEM ECU. The number on the side says 10-9100. 

We tried to run it in closed loop fueling, because it eats a shit ton of fuel, but it seems there is something fishy in the wiring. It has a Bosch LSU 4.2 Wideband sensor mounted in the manifold and the white signal wire is connected to pin 28(?) if we checked it correctly. I get a lambda reading, but it shows in O2 #2. When I try to run closed now it always compensates for the non existing sensor #1 as well. I manipulated the line to always show 1, but as soon as the target gets lower it will just start adding fuel worngly. 

I looked through the instructions folder, but I couldn´t find a fitting pdf and the help says it can use sensor 1 or 2 to regulate, but I couldn´t find a option to choose which sensor to choose. 

Now my load of questions:

Can I somehow define to only use the 2nd O2 sensor for closed loop regulation?

Is 10-9100 the correct ID of the ECU? All others seem to start with 30-xxxx

Does someone have the pinout/ manual of it?

Do we need 2 O2 sensors to make it run properly? I doubt the car has a cat....

The lambda reading seems strange and the setup wizard didn´t include a Bosch LSU. I think it was set up as an external gauge, which the car has, but it looks like the UEGO is wired straight to the ECU and they hijacked the signal wire for the gauge. The wiring harness is a nightmare... 


Thanks a lot in advance!


Last seen: 2 years 1 month ago
Joined: 02/26/2017 - 19:03
There will be a 30- number

There will be a 30- number sticker, find that and you can find a manual then. You only need 1 o2. Which is usually wired to the factory o2 pin in ECU.

Last seen: 2 months 6 days ago
Joined: 09/16/2016 - 18:02
What year Supra? Knowing that

What year Supra? Knowing that information will determine whether or not my answers to your questions are correct or not.

Assuming the most popular USDM 93-98 model, the correct AEM EMS part number is #30-1100. You should be able to find the instructions in the following directory of the computer AEMPro is installed on: C:\Program Files (x86)\AEM\AEMPro\Instructions

According to the pinout, Lambda #1 is pin 47B and Lambda #2 is pin 48B. When looking at the pin end of the ECU, the plug on the right is 'A' and the double-plug on the left is 'B'.

I haven't used the Series 1 software in quite some time, but I think you can change the O2 feedback sensor assignment for each injector. From within AEMPro, go to Options > Injector. Select each injector, and then click the radial button next to either 'Oxygen Feedback 1' or 'Oxygen Feedback 2' to assign sensor 1 or 2 to that injector. You shouldn't need two O2 sensors as long as the wideband is installed far enough down where the exhaust has merged into a single pipe. If memory serves, the Supra has two exhaust manifold "banks" that eventually merge into a single collector.

If the car is using the AEM gauge-type UEGO controller (#30-4100), there are two harnesses involved. One is a six-pin harness that connects the wideband O2 sensor directly to the gauge. The other is a four-pin harness that goes - Red: 12v Power, Black: Chassis Ground, White: 0-5v Output, Blue: Serial Output. The white wire from this four-pin harness is what should be going to either pin 47B or 48B on the ECU.