CU Safety Test Stop Fault
Siemens · DAsl Diagnostics and Alarms
What does F01773 mean?
A safety test stop fault has occurred on the Control Unit (CU) side, specifically indicating that the expected states of the Digital Outputs (DOs) were not fulfilled during a safety test. This means the external readback signal was not set correctly for a given test stop state (e.g., state 7), where an expected value was not observed. This issue compromises the validation of safety functions.
Common Causes
- Digital Output (DO) on the Control Unit (CU) side (e.g., for Safe Torque Off - STO feedback) is not switching to the expected state during a safety test.
- External wiring or feedback circuit for the safety DO is faulty (e.g., wire breakage, short circuit, incorrect load or feedback component).
- Incorrect configuration of the Safety Integrated (SI) function parameters relating to DO feedback monitoring or timing.
- Internal hardware fault within the Control Unit's Safety Integrated DO monitoring circuit.
- Mismatch between the actual feedback signal from an external safety relay or contactor and the expected signal as configured in the drive.
Repair Steps & Checklist
Click steps to track your progress.
- 1
Review the Safety Integrated (SI) function configuration and parameters (e.g., P0970, P0971, P0972) related to the digital outputs and their feedback monitoring on the CU.
- 2
Perform a controlled safety test stop and use a multimeter to measure the voltage state of the relevant Safety DO (e.g., on X20 terminals) and its feedback input during the test sequence.
- 3
Inspect the wiring from the Safety Digital Output on the CU to any external safety components (e.g., safety relay, contactor) and back to the CU for feedback for continuity and integrity.
- 4
Check the external safety components (e.g., safety relay contacts) for proper switching operation and contact integrity under load conditions.
- 5
Temporarily disable (with appropriate safety precautions and risk assessment) the specific safety output monitoring to confirm if the fault resides in the output or its feedback path.