Q: I unplugged mass air flow sensor

When you unplugged the part while the engine was running, the Electronic Control Unit (ECU) saw it as a component failure and lit up the check engine light. There will now be a code stored for the air mass meter. The check engine light may go off after about 50 drive cycles (a few weeks for most people) if the ECU doesn’t see any more problems, but the stored code will remain until it is cleared. You can have the codes cleared and the light put out by contacting Your Mechanic. They can send a technician to your home or office to read and clear the ECU right there on the spot.