I just bought a PS2 Fat console with this same problem for repair, and like somebody else commented: adjust the resistance of the potentiometers by just a little bit, it should work fine with dvds. Since the laser works fine with CDs, then obviously just adjust the DVD screw. It’s on the bottom of the laser assembly, it should be labeled DVD and CD under 2 screws which are used to adjust it. All you need is a Philips head screwdriver. If you want to be accurate with how you’re adjusting it, get a voltmeter and change it to the ohms setting. Sony sets it to 1100 by default, but you can make it lower to help the laser read the dvd better. Don’t go under 800 ohms though, or it could damage the lens permanently. Hopefully this helps, this is what fixed mine when I started tinkering. It’s obviously not the lens that needs to be cleaned if it can read CDs and not DVDs (since some of these people who answered obviously didn’t read your question thoroughly).