DIY 4A-GE Smallport EFI Wiring Pt.1: Identifying ECU Pinouts

After a long consideration, i have decided to do the wiring on my 4A-GE EFI system on my own. Or at least, TRY to do it myself first. I took a long observation of the wiring diagram that i had, and finally thought "Hey, i can do this.." and so it began our long journey on this DIY. I don't know what lies ahead since this would be my first time doing it. I may mess up during my try but i won't give up easily and will resort to someone else with better experience ONLY if i feel like there's no other way to finish it (or if i fry my ECU.. lol). Hence, i can't promise you this will be a thorough DIY but i'll do my best to reach the end. That being said, don't blame me if you fry your ECU following this DIY..

First thing we need to do before we get on to soldering and cable cutting, we need to identify the pinouts on our 4A-GE ECU. To do this, you need to open up the ECU box and take note of the markings on the ECU board next to each of the pins.
(click here for larger view of the image above)
The reason we need to do this is that smallport ECU pins might vary depending on the engine's country of origin so you have to be sure of the pinouts. For instance, USDM smallports would have different pinouts to JDM ones since they only have the AFM version, not the MAP. Do notice that my ECU part number is 89661-12590 so if you have the same part number, you can skip opening up your ECU. Or do it for the sake of learning, of course.

Here's the what i got on my ECU pins..
Can't see it? Click here for better view.
Notice that there are three connectors on my ECU with each having different number of pins. From left to right: 26 pins, 16 pins and 12 pins connector.

So what does each pin do? I gathered the information below from various source, which is here, here and my own post. On the table below, you can see the description of each pin and their function related to the EFI system or the car itself in general. Don't quote me on the table as i may misinterpret the source but i'd say it's good enough to give you an understanding of each pin's purpose.

26 pin connector

16 pin connector

12 pin connector

You should already notice that the pinouts are for MAP sensor based ECU and not for the AFM one. So if yours is AFM version, it will not be covered here. On the next part of this DIY, i'll show you how each pins are wired and explain a bit of how they function in the EFI system.