For BMW M52B25TU and M54 engines. Most commonly found in E46 and Later E39
 
*Instructions, after unplugging the battery and installing the ECU, reconnect the battery and attempt to start the car, *If the car does not start removing and bypassing of the EWS module maybe needed. 
Step 1: Make sure that your car does Not Crank (Engine Doesn't Turn Over).
Step 2: Remove your EWS3 Unit and put it on the passenger seat so you don't forget its location.
Step 3: Insert a 30amp / 25 amp / 20 amp max! Fuse into Pin 1 & 2 into the EWS3 Female plug (See Picture LINKED HERE). Remember there is No way the fuse will not fit, if you are having trouble simply turn the plug around and you will be fine.