Applicable Systems
S7-1200
S7-1500
S7-300
S7-400
LOGO!
SINAMICS
Symptoms
The BF (Bus Fault) LED flashes red. The CPU indicates a module not found error in the diagnostic buffer. The affected I/O module is not communicating with the backplane.
Possible Causes
- Module was physically removed or is loose in the rack
- Module has failed and is no longer responding on the backplane
- Backplane connector damage or contamination
- Module firmware is incompatible with the CPU configuration
Troubleshooting Steps
- Step 1: Check the physical seating of the module in the rack
Module is firmly seated with no visible gap at the backplane connector - Step 2: Inspect the backplane connector for bent pins or contamination
Connector is clean and all pins are straight and intact - Step 3: Verify the module's order number matches the hardware configuration in TIA Portal
Module part number matches the configured module exactly - Step 4: If the module is confirmed faulty, replace it with an identical unit
Replacement module is recognized by the CPU and communicates normally
How to Reset
To reset: 1) Power down the rack. 2) Reseat or replace the affected module. 3) Power up and verify the module is recognized. 4) Clear the diagnostic buffer. Caution: Always power down the rack before inserting or removing modules to prevent backplane damage.
Common Replacement Parts
- 6ES713-6BF00-0BN0: ET 200MP TM module replacement (Match the exact order number of the original module)
Frequently Asked Questions
- Q: Why is my module not found after a rack expansion?
The new module may not be configured in the TIA Portal hardware project, or it may be physically loose in the rack.
- Q: Can I hot-swap modules on an S7-1500 rack?
The ET 200MP supports module replacement under specific conditions, but always refer to the system manual for safe hot-swap procedures.
Source: Siemens S7-1500 System Manual, Edition 08/2023
Category: PLC & VFD