This might be helpful to other owners with Subaru engines.
Mine is a 1998 EJ25D and maybe this might help if your getting trouble codes. I didn't log the codes so I can't tell you the exact code I was getting but it had something to do with the transmission and the neutral position switch.
By grounding out the neutral position switch wire that seemed to solve that issue and there is a wire at the ECM that needs to be grounded if your using a manual transmission
View attachment Subaru Neutral Switch Wiring 1 of 2A.jpg
View attachment Subaru Neutral Switch Wiring 2 of 2A.jpg
This is the manual transmission wire that goes to ground
View attachment Subaru MT GroundA.jpg
Also by accident when I was working on the ECM grounds I disconnected the speed sensor wire. When test driving the car I noticed a lack of performance and the engine wasn't running as smooth as it once did. Not much longer a trouble code appeared saying there was an issue with the speed sensor. Got back home and realized what I did and reconnected the wire back up to the ECM and all was good again.
So if your not running a speed sensor the engine will run, but not as good as it could.
I think thats it for now.
The red/yellow wire at the starter relay tee's off and goes to the starter also. Picture doesn't show that. Thats how Subaru does that. They only show that one specific circuit and not if other circuits use it.
I found that out the hard way. I had one circuit wired in and found out later that another circuit used that same power source. Had to go back in and trace down that wire and then tap into it. Not much fun.