Technical Information K-Series Engine Swap
Many problems are caused by an incorrect approach to engine swaps. The simple logic is that the ECU was designed for use in an 02-04 RSX, so if you follow the RSX wiring it will work.
Tech - K20 Transmission swaps. explains the differences between 02-04 transmissions and the later 05-06 transmissions.
Tech - K20A Engine Swap Wiring explains the main wiring process and issues for engine swaps.
Tech - K20A Engine Swap Grounds shows what ground straps are needed and how the battery should be wired up.
Tech - K20A Engine Swap Fan Switch explains where the fan switch should be placed.