What is the weightage for the essay in the Great Lakes-Chennai PGPM process?

There is no specific weightage for the essay in the Great Lakes Chennai PGPM process. However, it is generally considered to be an important part of the application process as it allows the admissions committee to gain a better understanding of the candidate's qualifications and goals. 

Great Lakes focuses on the overall profile of the candidates and these essays are a good mode of evaluation of the candidate's skills. Your goals and passions can be written in a lucid manner that convinces the recruiter to select you.

So, I will recommend you focus on submitting a well-written, clear, and concise essay that effectively communicates your qualifications and goals.