Ok now I cant say this will work for everyone I just know that tit worked for me.
So here I was decided to reflash my car back to stock cause a got some bad gas and didn't like the idea of running stage 2 with bad gas so I reflash and half way through the reflash I got the low voltage error ok now I panic I run in the house get out the book and start reading the book says ECU more and likely needs to be replace again more panic.
Well I began searching for a new ECU and no luck on finding one that's not 700$ so I have a great idea, The ECU is already messed up can hurt to try to reflash so I go out to the car hook the green wires backup and the little clear connecter and plug in the access port and it says choose map that good so I go straight to stage 2 and hit send well it goes through the process and about 10 mins later its done so I cross my finger get in car and turn the key. Car starts up and runs great minus the bad gas so I go back home and reflash to stock drive it on stock till the gas issue is fixed and the back to stage 2 this happen about 2 weeks ago and still not a problem in the world. Just figured id add this incase someone else has this problem.
Like I said I cant say it will work for everyone but it worked for me and my wrx is an 03.
Hope this helps

 

you can find 02/03 stock ECUs on nasioc for around $200