But I don't have the radiocode. Any idea guys?

 

The best thing to do is either look for a owners manual or go to the dealership.

 

Read this: https://honda-tech.com/forums/honda-civic-2001-2005-78/faqs-guidelines-read-before-posting-2101211/

Then this: https://honda-tech.com/forums/showthread.php?t=2247386

There is a link in the FAQ's for this: https://honda-tech.com/zerothread/1775364




On a side note: Your thread title needs to relate to your opening post. In this case, "radio code" would have been a better choice for a title than "just got 2003 civic"