That in of itself should not be too much of a concern. Couple things going for you:
1) Undergraduate grades are weighed more heavily than graduate grades, because they are the common denominator (ie not everyone has graduate grades)
2) Engineering is viewed as the most difficult of all specializations to pursue and as such there is an anticipated discount to those grades.
A strong GMAT will be a key factor to your sucess... but don't forget there are many others too.