I changed the battery on my truck and the stereo went into enter password and dont know what it is and now it is locked
Assuming you have tried standard default codes 0000, 1111, 1234...
Clarion models keep the security code in non-magnetic memory inside the unit.
only way to reset is to return it to clarion to have it cracked and
reset using their proprietay software, and/or replace the flash memory
Clarion authorized service centers cannot even do it (like Kenwood can)
If it says CODE, you can attempt to enter a code. If it says LOCK - after 7 attempts, you must wait 15 minutes.
Hope this helps