legacycentral bbs

Hey BBS,

Just a quick summary, I've completed a rebuild on my Impreza motor which is using a Rob tune ECU. In the recent rebuild I've converted my ignition system to COP from wasted spark.

When I went for first start up I wasn't able to get the car to run. It sounded clearly as though the firing was off.

Here is what I've concluded, that either the factory service manual is incorrect in the pin placement at the ECU of the ignition system, or in some case there is different pin placements on different ej20g ECU's.


I originally followed the Subaru FSM which has the ecu pin placement as follows:

Ignition #4 - pin 7 of 26
Ignition #3 - pin 8 of 26
Ignition #2 - pin 9 of 26
Ignition #1 - pin 10 of 26

1996 JDM ej20g ECU pinout picture:


With no luck trying the Subaru FSM pinout and a bit of digging around I found a pinout diagram sent to me by Haltech. I noticed that the Haltech pinout differed from the Subaru pinout, so I gave it a try and sure enough got the car running on all four cylinders.

Haltech pinout as follows:

Ignition #4 - pin 7 of 26
Ignition #3 - pin 9 of 26
Ignition #2 - pin 8 of 26
Ignition #1 - pin 10 of 26

Haltech pinout picture:



Sorry if this old news, but I didn't read anywhere of others facing this issue, unless I'm crazy, maybe, probably.

So output 2 and 3 are reversed in the FSM. Wouldn't be the first time the fsm was wrong. I remember a bunch of people attempting the COP swap going back since it ran poorly, or didn't run at all. Nice work

Yeah...good work.

I wonder if the FSM would be for the following year? Was '96 a transition year for the JDM/EDM/AUDM versions? I have NO experience w/either COP nor the next gen of the EJ20xx ('96+ EJ20K ?).

But if the FSM's are translated, would that explain some of the errors? Or just 'human error'.

NASIOC LINK w/some ECU stuff.

wtdash wrote:Yeah...good work.

I wonder if the FSM would be for the following year? Was '96 a transition year for the JDM/EDM/AUDM versions? I have NO experience w/either COP nor the next gen of the EJ20xx ('96+ EJ20K ?).

But if the FSM's are translated, would that explain some of the errors? Or just 'human error'.

NASIOC LINK w/some ECU stuff.

Sure, human error is viable, even more so after translation.

Looking at the pinouts for 96+ it would appear that everything is 2 channels that share 1&2 and 3/4. I don't believe the pinout is inaccurate too the ej20g, but the region is questionable.

Interestingly​ I've found a post from Rob (RobTune) that depicts a " wrx COP how to". In that write up there is a diagram showing the ignition signal wires leaving from the coils, going through an ignitor, and then to the ECU. In that diagram the ECU pin placement is as I've done.

In the post from Rob you can see that he has Illustrated the connectivity within the ignitor.

This is how it looks in the 1993-1996 F.S.M :



Without seeing the routing within the ignitor it's difficult to say where the connections lead.



So really this just adds to the confusion. I don't believe that I'm interpreting the F.S.M diagram incorrectly but maybe so. Logic says I'm seeing it right. It's the ECU pinout that's most confusing.

If only Rob or Phyrra could chime in and clear the fog.

Going to be wiring my coil on plug setup following this soon. I'm assuming this worked out Dankberries?

mike-tracy wrote:Going to be wiring my coil on plug setup following this soon. I'm assuming this worked out Dankberries?

Yep, it definitely worked.
Worst comes to worst you will know right away if it doesn't work lol.

Dank & Mike,

Just to clarify, and hopefully this can answer your questions and help with a smooth and more importantly correct install, yes there is a discrepancy between the EJ20G FSM from Subaru and the Haltech diagram. What has caused confusion on the FSM in the past is the assumption that the actual numbers listed, #1, #2, #3, and #4, were interpreted as cylinder numbers, which is not true. What the JDM FSM references in those numbers are Firing Order, which for all EJ's is 1-3-2-4.

So, breaking it down both should be read as follows:

FSM (F.O.)-----Cylinder #-----Harness Pinout-----Haltech Diagram
-----#1-------------#1--------------Pin 10----------------Pin 10
-----#2-------------#3--------------Pin 09----------------Pin 09
-----#3-------------#2--------------Pin 08----------------Pin 08
-----#4-------------#4--------------Pin 07----------------Pin 07

So, technically, both the FSM and Haltech are correct, it's just the FSM is a bit misleading again by not specifically stating it's referencing firing order and not cylinder number. Only reason why I can attest to this info is that I just finished up with my patch harness for plug-n-play on the EJ20G ecu's on our USDM EJ22T factory harnesses and have been through about a million forums, at least on several different occasions, getting everything together. Good luck on the builds, keep us posted!

I had suspected an incorrect interpretation, luckily problem solving lead me to success.
Thanks a bunch for the clarification, hopefully this helps others for the future!

Thanks for sharing this information guys!