Removal and replacement of the ECU in E9x M3 is very simple task and takes only about 30 minutes. Here are step by step instruction: removing the driver side air conditioning filter cover. Air conditioning filter cover is a triangular located just in front of the firewall. Remove the three screws holding the air filter cover. Even removed filter coverage will still be attached by means of an air temperature sensor. Let the sensor attached and just rotate the filter cover by the way. Air temperature sensor is held a rotating Lock ficture and two compression tabs. Do not draw on wiring remove tabs compression.Download PDF document