Why does my Bosch D8125 Control Unit transmit PT BUS TROUBLE reports?
- Nnicole65Aug 13, 2025
A short on either the Data Expansion Loop or the ZONEX data terminals generates a PT BUS TROUBLE report on the Bosch Control Unit. While the short remains, the control panel responds as though the sensor loop for each point connected to the POPEX module was shorted. Check the wiring for shorts. Also, ensure all POPIT and OctoPOPIT address switches are set correctly. POPITs cannot be used for Points 128 or 248, and OctoPOPITs cannot be used for Points 121 through 128 or 241 through 248.