Hello Aswin,

PCB students can also apply for IISER.But to apply for BS programs in Economics and Engineering Sciences , you need to have studied maths in 10+2 level.The IISER aptitude test consists of questions from all four science subjects( Physics, Chemistry, Maths and Biology) with 25% marks on each section. You can refer the following link for more details on the exam.

https://engineering.careers360.com/articles/iiser-syllabus-exam-pattern