Resolving G120 CU240E-2 Safety Fault 30683 SLS Not Active

Problem Overview

During extended safety commissioning of a SINAMICS G120 drive equipped with a CU240E-2 PN-F control unit, fault messages F30683 SI Mtn P2: SLS enab miss and F1683 SI Mtn P1: SLS miss appear on power-up. These faults prevent the drive from acknowledging the safety configuration and going into Run, even when the user has explicitly intended to operate with only STO and SS1 (no SLS, no SDI, no SSM).

The error occurs on the IOP (Intelligent Operator Panel) wizard path and is the same fault class that STARTER/Startdrive would raise when an extended safety function has been globally activated by default but the user has not finalized its disablement. The cause is a commissioning behavior in firmware versions that support Safety Integrated Extended Functions: when the extended safety wizard finishes, STO, SS1, and SLS are written as statically active. SDI and SSM are not pre-activated and therefore do not require manual deactivation.

Affected Products and Firmware

Verify the firmware with parameter r0018 (Firmware version) on the control unit. If r0018 < 4.4, extended safety functions are not present and the parameter indices shown below do not exist. The CU240E-2 PN-F operating instructions document the firmware dependency in section "Safety Integrated".

Root Cause Analysis

SINAMICS G120 extended safety commissioning follows a fixed parameter template. When the user enters the extended safety wizard (IOP path: Menu → Commissioning → Safety Integrated → Extended Functions) and assigns STO to an F-DI and SS1 to an F-DI, the wizard writes the following defaults at the end of the assistant:

• p10022 SI STO F-DI = selected F-DI (e.g. DI 2 → F-DI0)
• p10023 SI SS1 F-DI = selected F-DI (e.g. DI 1 → F-DI1, or via PROFIsafe)
• p10026 SI SLS F-DI = [0] statically active (default; written by the wizard)

On the next power-on / warm restart the drive evaluates the active safety functions. Because SLS has been written as "statically active" but the user has not configured a valid SLS limit, the safety monitoring channel raises the missing-function fault. The fault is reported on both monitoring channels:

• Channel 1 (processor 1) → F1683 SI Mtn P1: SLS miss
• Channel 2 (processor 2) → F30683 SI Mtn P2: SLS enab miss

The two messages are not duplicates. F1683 indicates that the safety function block for SLS is required by configuration but not present in the parameter set. F30683 indicates that the enable signal for SLS has not been sourced to a valid F-DI or PROFIsafe bit. Both faults are raised in parallel and both must be cleared.

Parameter Reference

The following parameters control the static activation and F-DI selection of the safety functions on the CU240E-2. All are indexed under p10xxx and can be read or written from the IOP expert list, STARTER parameter list, or Startdrive offline/online view.

Statically active means the function is permanently enabled regardless of any F-DI or PROFIsafe telegram bit. The function will be considered as "selected" in the safety logic. Statically inactive disables the function entirely so it does not participate in the safety state evaluation. The values 0 and 1 are the only ones that bypass the F-DI/PROFIsafe interface for the function in question.

Step-by-Step Resolution

Use the following procedure to complete commissioning with only STO and SS1. The procedure is the same whether you start from a fresh wizard or from a half-completed state where faults 30683/1683 are active.

1. Clear the safety password. If a Safety Integrated password is set, the parameters below are read-only. From the IOP: Menu → Commissioning → Safety Integrated → Change password. Default Siemens password on a new drive is 0. STARTER/Startdrive path: Drive → Safety Integrated → Password.
2. Open the expert parameter list on the IOP (Menu → Parameters → Expert list) or the equivalent STARTER parameter view.
3. Set p10022 (SI STO F-DI) to the F-DI index of your choice. The CU240E-2 has two F-DIs, each consuming two standard digital inputs. With macro 7, DI 0 + DI 1 form F-DI 0 and DI 4 + DI 5 form F-DI 1 (or the DI numbering used by the macro). Set p10022 to [2] F-DI 0 or [3] F-DI 1 as desired.
4. Set p10023 (SI SS1 F-DI) to the other F-DI. Verify the two F-DIs are not in conflict (each F-DI occupies 2 digital inputs; you cannot have more than 2 F-DIs total on CU240E-2).
5. Set p10026 (SI SLS F-DI) to [1] statically inactive. This is the critical step that resolves the 30683/1683 faults. The wizard does not do this automatically; you must set it manually.
6. Set p10030 and p10031 (SI SDI+ and SDI-) to [1] statically inactive. Although the wizard does not enable these by default, the G120 firmware will raise an internal consistency warning if p10030 and p10031 are set inconsistently. Setting both to inactive guarantees a clean state.
7. Set p10049 (SI SSM enable) to [1] statically inactive. SSM is an output indication, not a stopping function, but it must be intentionally disabled when not in use.
8. Set p10006 (SI acknowledge internal event). Two valid options exist:
     - [1] statically inactive: any pending internal safety event cannot be acknowledged via F-DI. Only power-cycle or PROFIsafe acyclic command can clear. Recommended for bench commissioning.
     - [2] F-DI 0 or [3] F-DI 1: use a physical acknowledge pulse to clear events. Required in many machine applications because the F-DI channel provides the safe feedback path.
     - [0] statically active: events are immediately acknowledged. This is rarely used in production because it can mask legitimate internal events.
9. Set p10017 (debounce) to 1 ms for the standard configuration in this question. Valid options on CU240E-2: 1 ms, 2 ms, 5 ms.
10. Set p10018 (changeover tolerance) to 500 ms. This is the maximum time allowed between the two physical inputs of an F-DI to be considered "simultaneous".
11. Save the parameters to the CF card (or to the control unit) and power cycle the drive. On the IOP: Menu → Commissioning → Save parameters to EEPROM. On STARTER/Startdrive: right-click the drive → Copy RAM to ROM.
12. Verify the faults are gone by reading r0947 (fault buffer) and r2122 (alarm buffer) on power-up.

Verification

After the procedure above, perform the following functional verification before placing the drive into service:

1. Read r9771 (SI common setpoint / S_ZSW1) and confirm bits for STO and SS1 reflect the F-DI inputs. SLS, SDI, and SSM bits must read "not selected".
2. Read r9722[0] (SI status word, channel 1) and r9722[1] (SI status word, channel 2). Bit 0 = STO active, bit 1 = SS1 active, bit 4 = SLS active, bit 12 = SDI positive active, bit 13 = SDI negative active.
3. Force each F-DI low and confirm the drive transitions to the expected safe state (STO causes immediate pulse suppression; SS1 first brakes along the configured ramp then transitions to STO).
4. Check r0947 for any F30683 / F1683 / F1690 / F30690 entries on the fault buffer. None should be present.
5. Run the acceptance test per the SINAMICS G120 Safety Integrated Function Manual, chapter "Acceptance test". The wizard in STARTER (Safety Integrated → Acceptance test) generates a log file that must be signed by the safety officer.

IOP vs STARTER / Startdrive

The IOP extended safety wizard is a guided sequence that writes the same parameters that a direct parameter list edit would set. The behavior difference is that the IOP wizard never asks the user to deactivate SLS after the fact. It expects the user to recognize that p10026 = [0] statically active is a default and to override it manually. STARTER and Startdrive surface the parameter values in plain text in the Safety Integrated screen, so the discrepancy is more obvious. The G120 operating instructions for the CU240B-2/CU240E-2 family state that STARTER is the recommended tool for Safety Integrated commissioning because it provides immediate online cross-checking between parameters p10022, p10023 and p10026, and it directly exposes the PROFIsafe telegram configuration under Communication → PROFIsafe.

If a laptop is not available, the IOP procedure is functional but requires manual parameter edits in the expert list after the wizard completes. The expert list path on the IOP is: Menu → Parameters → Expert list → [select parameter number] → Edit. Use the up/down arrow keys to scroll through the F-DI selection, then press OK to commit. Repeat for every parameter listed in the procedure above.

F-DI Configuration Details

The CU240E-2 has two fail-safe digital inputs (F-DI 0 and F-DI 1). Each F-DI is realized as a pair of standard digital inputs wired in parallel and compared for discrepancy. With macro 7 (default ProfiNet control + manual/auto switch on DI 3) the input mapping is:

The two F-DI inputs are routed through r0722 (status of digital inputs) to the safety monitoring logic. The IOP "I/O Status" screen displays the raw DI status. Because the safety functions consume the F-DI channels rather than the underlying digital inputs, the screen will only show one entry per F-DI pair (DI 4 in the case of F-DI 1) when SS1 is configured but no other function is using the input. This is expected behavior and is documented in the operating instructions section "Status display of the digital inputs".

SS1 Behavior on the G120

SS1 (Safe Stop 1) on the G120 comes in two sub-variants selectable via p10023 and p10024:

• SS1 with OFF3 ramp (SS1-r): the drive decelerates along the configured OFF3 ramp (p1135) and then transitions to STO. The time in SS1 is monitored by p10025 SI SS1 delay time (default 200 ms minimum, 30000 ms maximum).
• SS1 with speed ramp (SS1-t): the drive brakes along a brake ramp derived from the speed setpoint. Less common on CU240E-2; refer to the Safety Integrated function manual.

For typical machine safety stop applications, SS1-r is selected and the time is set to be slightly longer than the worst-case deceleration time. If the drive cannot decelerate within the configured time, the system falls back to STO automatically. This fallback is not the same as SLS being missing, and the fault codes are different (F1690 "SI Mtn P1: STO discrepancy" or F30690 "SI Mtn P2: STO discrepancy" for SS1 timing problems; the SLS missing faults are F1683 / F30683).

SI Internal Event Acknowledgment (p10006)

The CU240E-2 raises internal events when the safety state machine detects an inconsistency that requires operator intervention. Typical events include:

• Forced checksum change (CRC mismatch) after parameter download.
• Acceptance test required (drive is in "safety commissioning" state and not yet accepted).
• Stuck-at fault on an F-DI (one input of the pair permanently low or high while the partner toggles).

p10006 selects how these events are acknowledged. The user in the original question observed that faults could not be cleared after setting p10006 = [0] statically active. This is correct: with statically active acknowledgment the drive tries to acknowledge internal events at every power-on, but if the parameter set itself is inconsistent (e.g. p10026 = statically active without a configured SLS limit), the acknowledgment is rejected and the faults remain. The correct fix is to remove the underlying inconsistency (set p10026 = [1] statically inactive), not to change the acknowledge mode.

Diagnostic Parameters

Troubleshooting Matrix

Documentation References

The following Siemens documents contain the canonical parameter definitions, fault code tables, and acceptance test procedures referenced above:

• SINAMICS G120 with CU240B-2 and CU240E-2 Control Units — Operating Instructions (PDF)
• SINAMICS G120 / G120C / G120D / G120P Safety Integrated Function Manual (searchable on the Siemens Industry Online Support portal under entry ID 109751320)
• SINAMICS G120 Parameter List Manual (entry ID 109751321)