Clarion: Unlock radio, Looking for the code?

Good Morning,
I had to change my car battery and now the Radio wants a Security Code. I tried a little, now it shows "error" on the display and I cannot enter code anymore. Is there a solution still? Here are the details:
Clarion CD Radio
Model: PW229480(D)
Serial Nr. CL0402Y0429411

Kind regards, Haro