It is unlikely you'll be eligible for AP ECET counselling with a current backlog in your diploma.

Most sources mention that candidates must possess a Diploma in Engineering and Technology from the State Board of Technical Education of Andhra Pradesh (or a recognized AICTE institution) with a minimum percentage (usually 40-45%) to be eligible for AP ECET counselling.Since you have a backlog, you likely haven't received your diploma certificate yet. This might make you ineligible for counselling at this stage.

If you clear your backlog and obtain your diploma certificate before counselling begins (usually July 2024 for AP ECET), you might be eligible to participate.

https://engineering.careers360.com/articles/ap-ecet-exam-centres

I Hope it helps!