Code Killer is a Circuit Board filled with components that defeat Diagnostic Trouble Codes (DTC) - solving up to 9 common DTCs related to Subaru engine swaps. This is optional and these DTC's don't affect performance of your engine, but it is a good way to "clean up" your install and make your Malfunction Indicator Lamp (MIL)/Check Engine Light (CEL) more useful. Your MIL/CEL will only turn on when a critical DTC is triggered. We recommend installing near the Subaru ECU. Code Killer comes with a diagram and you can locate your DTC causing sensor wires at the ECU pinouts page here: Pinouts

For newer Subarus (2002+ Turbo or 2005+ Subaru, Any Model) you can use the Subaru ECU Flash service which will eliminate many more DTC's. See more info here: Subaru ECM Flash