There are two master codes for a CP4 control panel. Code 6343 for high level access, and code 0000 for low level access. For more information please view the installation manual: https://www.reznor.co.uk/wp-content/uploads/2025/09/Benson-CP4-Installation-Manual-EN-2009-06-GB-CON-016-0609.pdf.
What is the master code for a CP4 control panel?
Information on Reznor's range of control panels