Is there a sensor that could be causing the E02 error on the Pixma E510?

Yes, there are paper detection sensors inside the printer. If one of these sensors is faulty or obstructed, it can trigger the E02 error even if paper is present. It's difficult to directly troubleshoot sensors without technical expertise, so carefully check the paper path for any obstructions near sensor locations, and consider seeking professional repair if cleaning doesn't work.