When I open carcols.ymt from update update.rpf x64 data with notepad I get all strange lines (unreadable). What am I doing wrong? In my nypd pack I could read it.

That is because the stock carcols.ymt is encrypted. In order to read it, you would need to download a unencrypted version of it.

3 minutes ago, flwpheonix said:

That is because the stock carcols.ymt is encrypted. In order to read it, you would need to download a unencrypted version of it.

Do you have suggestions on which mod to download? I can't remember which one I downloaded for my other pack

Why not just use the one from the NYPD one?

3 minutes ago, flwpheonix said:

Why not just use the one from the NYPD one?

It crashes when I load the game with my other pack 

What other pack are you using?

4 minutes ago, flwpheonix said:

What other pack are you using?

custom made GCPD pack where I didn't edit the carcols file 

That would be why the NYPD carcols is crashing the game. If the GCPD pack has additional entries besides the stock ones, then the game is looking for those entries with the NYPD carcols, and cannot find them. The best thing to do is copy the entry for the nypd one (I think item number 13, or search NYPD in the nypd carcols) copy that then paste into the GCPD carcols. In order to avoid conflict, renumber the NYPD to something like 60 or so, and make sure your carvariations is pointing to that siren number that you renamed it to.