I want to say that that tube is the vacuum tube that goes into the cabin. Its this tube that feeds vacuum to the HVAC controls to work the actuators that open and close duct valves. I think the EGR valve might also get its vacuum feed from this tube. If its leaking the vacuum pressure in the system will be less than otherwise. If thats the case the EGR won't work properly. The EGR has a sensor on it to tell the computer its position and therefore the ammount of exhast gas its allowing into the intake stream. If the computer thinks its getting an incorrect reading from the EGR valve sensor it will turn on the check engine light.
If it is the case then I think that resetting the ECU will eliminate the check engine light, but it will come back on after a little while.
