i can see how dodgy this would sound, but i need to either remove or bypass my standard key immobiliser. ive just completed a jdm engine swap into my adm rex and after 6 days of headaches and failure re earthing and re wiring nearly my entire car, im lead to believe that the only other reason that im not getting power or ground to my ecu, (which is stopping my fuel pump priming and pumping and my plugs from sparking) is the fact that my immobiliser isnt allowing power or earth to reach or leave the unit to contact the relays and sensors.

i have manually earthed each individual ecu ground wire and put 12v to the main 12v ecu sources but the ecu is still not allowing power out to the relays. since doing this i now have a CEL (which indicates my ecu is recieving power) and my immobiliser light is flashing now when the key is turned to the on position. (it usually turns on when the key is off and off when in start position.)

so basically im thinking (previous to me re earthing and re powering the ecu) that somehow the jdm motor isnt allowing my key to disconnect the immobiliser so the ecu is just sitting there like a vegetable not recieving or sending any signals at all.

as you can see im in one hell of a pickle and would appreciate any input on my crappy situation!

thanks kindly

The JDM engine wil have no effect on the wiring. How much JDM loom has been fitted (if any) and did the engine start on the original Aus spec ECU? Possibly refit it if you still have it and establish a base line before getting any more frustrated. One change at a time to reduce confusion etc.

Its just the engine loom which is jdm. I have an apexi power fc but havent put it in yet, im still using the aus spec ecu and car harness. I basically took out the aus engine and dropped in a jap one using the loom that came with the motor

The old engine started first time every time. This swap is just an upgrade.

The immobilizer system is between the chip in the base of the key, the key reader in the steering column and the ECU. It doesn't care what engine is fitted.
There my be an additional alarm/immobilizer fitted that's giving you grief perhaps?
As long as the STi engine was the same era as the original and the pins match on the connectors then it should be no different electrically to the original. The only additional sensor a Jap STi has over an Aussie WRX is an air temp sensor in the duct to the airbox but they start and run ok without it.
Is the cam timing and everything with the engine in good order?

Hmmm well yeah i had all the timing done before i fitted the engine. I know theres differences between jap and aus looms so i thought maybe the jap engine loom was diverting power and ground into the wrong pins on the ecu? And maybe not giving the immobiliser the power or ground to work

Not in my experience. I'm not saying it's impossible but I know that in the past I have removed JDM WRX (non STi) and plugged directly into Aus spec WRX and roared off into the dust without a care in the world.

I would say go back over everything you have fugged around with and make it back to stock. Cambelt done? (if so who did it? I have seen numerous cambelts out of timing)

I had a trusted mechanic do it. Hes delt with subarus hundreds of times. Ive got it running now, you were right about the immobiliser not being the culprit, but i didnt figure out what the issue was. I spliced cable into all the grounds on the ecu and gave them a new earth and put a constant ground to the fuel pump relay so now when the key is turned on it doesnt prime it just comes on. Ive been over and over it and cant fugure out why the grounds are so bad