F25
Siemens
Controller Communication Bus Fault
Controller displays F25 CAN Bus Communication Error; some functions may be disabled.
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Safety Warning
This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.
If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.
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Possible Causes
Loose CAN bus connectors, Damaged communication cable, Incorrect termination resistors, Failed expansion module on CAN network
How to Fix / Troubleshooting
Safety first: Turn the controller to OFF and disconnect battery power before unplugging or plugging communication cables.
- Inspect CAN wiring: Locate the CAN bus cable (often twisted pair) linking the Siemens controller to expansion modules (e.g., remote display, ATS interface). Check for cuts, abrasions, or crushed sections.
- Reseat connectors: Unplug and firmly reconnect each CAN connector, ensuring locking tabs engage.
- Check termination: Verify that termination resistors are installed only at the ends of the CAN bus, as specified by Siemens. Incorrect termination can cause F25.
- Isolate faulty module: Disconnect modules one at a time from the CAN bus and power up the system. If F25 clears when a specific module is removed, that module may be defective and should be replaced.
- Retest: After repairs, restore normal wiring and confirm that communication is stable and F25 does not reappear.
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Repair Difficulty
Medium
3/5
Required Part
CAN Bus Communication Harness
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