AMIE Online Grade Card

http://online.ieindia.info/Login.aspx?Event_Id=326 

You are not passed if you get C grade in three subjects and D grade (in last attempt) in remaining subject. 

That is because for PASS, you must get B grade in at least one subject (Section A, Diploma Stream) to make total CGPA equal to 6 or more.

Examples:
(1) C, C, C, D (D in last attempt). You have to reappear in subject with D grade
(2) C, C, B, D (D in last attempt). PASS
(3) C, C, C, C. PASS

To know CGPA calculation method, click here

CGPA  = sum of overall subject grades/number of subjects

For one to PASS the CGPA >= 6 that means your overall grade total should be >=24.