With the radio on, press and hold buttons 1 and 6 simultaneously for about five seconds. The pre-code should flash on the display.
Have a working free method we missed? Car communities often share working serial-to-code calculators – check dedicated Renault forums for the latest links.
Why does this work? Renault dealers have access to the "Dialogys" or "CLIP" system. When you bought the car originally, that radio code was linked to your VIN. They can retrieve it in 30 seconds. Most dealers do not charge for this because it builds customer loyalty. If they try to charge you a "diagnostic fee" ($100+), hang up and call a different Renault dealer.