I have a friend who swapped a complete 2004 powertrain into his legacy GT. The wiring for the computers are identical but he can't get the car to start with the STi ecu. I would prefer to start with tuning the '04 ECU because the tables are better known and it matches the engine exactly. With that ECU plugged in I get an HC error on the dash and ecuflash will not talk to the ECU at all. The legacy GT ecu runs the car OK (haven't hooked a wideband to it yet)
Does this sound like an immo problem? The original key is available as the powertrain came from another friend's car. I suggested getting a cheap key cut then hold the original STi key at the ignition and turn the key on with the cheapo to see if that works. In my experience most immo codes are stored on an eeprom on the ECU but have they been figured out?
-Michael