The HP Envy printer is printing very faint images, even after cleaning the print heads. What could be the problem?

This could indicate a failing print head or a significant ink supply issue. While cleaning helps, a severely clogged print head might not be fully recoverable. Try running a few test prints with different document types to see if the issue persists. If the problem continues, consider replacing the print head (if possible for your model) or the ink cartridges.