The Main Engine Harness that has a 54 pin connector at the back of the engine bay at the firewall is made of two very large connectors that due to their location, quite common for them to be damaged Fix it up with this replacement plug housing.
Select Connector or Receptacle
Fits all
2005-2014 Legacy & Outback
2007-2013 Forester
2008-2014 Subaru WRX & 2008-2021 STI