BMW Repair: air filter M3 e 46 2004 smg, mass airflow sensor, m3 e 46

Question
All I wanted is to clean my air filter. In order to take the filter out I unplugged the sensor out of its place when car was running it try to die on me but managed to idle then I shut the car off and proceed I finished placed the sensor to its place start the car back on and there it was service engine soon light came on. Can you please advise WHY? it did that and how to fix it. Thank you in advance for your help

Answer
Rush, never unplug any sensor or electrical component while the engine is running unless you know what it will do. You logged a fault for the Mass airflow Sensor. If you have enough drive cycles without the fault the light may extinguish on it's own. If check Engine light does not go out then you will need to have the fault memory cleared with a scan tool.
-Evan