SINAMICS G120 CU240-PN: Resolving Stuck Quick Commissioning (P10=1, P1910=1)

When a SINAMICS G120 power module paired with a CU240-PN control unit is power-cycled to clear a fault and the drive refuses to enable, with the RDY (ready) LED flashing on a steady 1 s cycle, the inverter is almost always reporting that parameter P10 has reverted to 1 (Quick Commissioning in progress) and P1910 has reverted to 1 (motor data identification request). This is not a hardware fault; it is the drive's commissioning state machine announcing that the user has not yet finished or saved the quick-commissioning sequence. The drive cannot be released for normal operation until P10 returns to 0 and the new parameters are committed to the non-volatile memory card or internal flash.

1. Affected Hardware and Drive Family

This issue applies to the SINAMICS G120 modular drive family when assembled with the Control Unit CU240-PN (PROFINET variant). The CU240-PN supports PROFINET IO, Modbus TCP, and EtherNet/IP and is offered in two firmware lines: the Standard line (Firmware V4.x and later) and the Safety Integrated (F) line. The quick-commissioning behavior described here is identical across both lines because the parameter structure is shared.

The CU240-PN's parameter interface is governed by the SINAMICS parameter handbook, and the operational state is mirrored on the on-board LEDs. Always cross-check against the SINAMICS G120 with CU240B-2/CU240E-2 Operating Instructions for the firmware version installed on your unit.

2. Symptom Matrix

3. Parameter Reference

The following parameters are central to the failure mode described in this article. All are read/write unless marked otherwise, and they live in the SINAMICS parameter tree accessible through the IOP-2, BOP-2, STARTER, or Startdrive commissioning tools.

4. Root Cause Analysis

The CU240-PN keeps a separate "commissioning state" in addition to the actual parameter values. The state is reflected in P10 and r3998. The following chain of events produces the symptom:

1. The operator (or a fault handler, such as a PLC block that watches F faults) powers down the drive to clear a trip.
2. During the previous session the user entered Quick Commissioning (P10 = 1), changed motor nameplate data (P304, P305, P307, P311, etc.), and saved with RAM-to-ROM — but the final confirmation step (setting P10 = 0 at the end of the wizard) was either skipped or interrupted.
3. On the next power-up, the drive detects that the commissioning flag is still set, so it auto-restores P10 = 1 and P1910 = 1 to prompt the user to finish the wizard.
4. Because P10 = 1, the run-enable logic in the drive's sequencer (see SINAMICS state diagram in the function manual) refuses all ON commands. The RDY LED flashes green at 1 Hz to indicate the "Commissioning" substate.
5. Because P1910 = 1, the next ON command will instead trigger a static motor identification cycle (the drive injects pulses and measures stator resistance) before releasing the motor for speed control. Until that measurement completes successfully and the parameters are saved, the RDY LED will keep flashing.

5. Diagnostic Procedure

Before applying any fix, confirm the diagnosis using either the IOP-2, BOP-2, STARTER (V5.x or later), or TIA Portal Startdrive (V15 or later). The diagnostic checklist below follows the engineering workflow used in Siemens field service reports.

5.1 Read-Out via BOP-2

1. Connect the BOP-2 to the CU240-PN. Apply control voltage to the unit.
2. Press ESC to enter the parameter menu.
3. Navigate to P0010 and confirm the value is ≠ 0 (any non-zero value confirms the drive is in a commissioning substate).
4. Read P0003 to identify the current access level. If it shows 1, raise it to 4 (see step 6.1).
5. Read P1910 to confirm the motor-identification request flag.
6. Read r3998. If r3998 = 1, the unit has never been properly commissioned; if r3998 = 0 and P0010 ≠ 0, the previous session was interrupted.
7. Read the alarm buffer (menu MENU → DIAGNOSTICS → ACTIVE ALARMS) and record the highest priority alarm A code (typically A07980, A07981, A07991 if commissioning is incomplete).

5.2 Read-Out via PROFINET (STARTER / Startdrive)

1. Establish an online connection to the drive via PROFINET or the diagnostic Ethernet port on the CU240-PN.
2. Open the Expert List and filter parameters containing 10 in their number.
3. Confirm the values of P10, P1910, r3998 as in 5.1.
4. Inspect the Control & Status word: STW1 bit 0 (ON/OFF1) and STW1 bit 3 (Enable operation) will be acknowledged, but the drive status ZSW1 will report bit 0 (Ready to switch on) = 1 while bit 1 (Ready to operate) = 0 and bit 2 (Operation enabled) = 0.

6. Resolution Procedure

There are three engineering-accepted recovery paths. Apply path A first; only escalate to B or C if the drive rejects the parameter write.

6.1 Path A — Close Commissioning Through P3 / P10 and Save

1. Set P3 = 4 (Service access level). This unlocks every commissioning parameter.
2. Navigate to P10. Confirm the displayed value (should be 1).
3. Set P10 = 0. This tells the drive that the quick-commissioning sequence has been completed.
4. Set P1910 = 0 only if you do not want the drive to perform an automatic motor identification on the next start command. If the motor is connected and uncoupled (or safe to be energized), leave P1910 = 1 to let the identification run and produce accurate stator resistance values.
5. Execute P971 = 1 to copy the changed parameters from RAM to the non-volatile memory. The BOP-2 will briefly show "Busy" and then "Done".
6. Optional: execute P977 = 1 if BICO interconnections were also modified during the session.
7. Power-cycle the control unit (24 V off, then on) and confirm P10 = 0 is still 0 after the reboot. If P10 = 0 persists, the recovery is durable.

6.2 Path B — RAM-to-ROM From the Keypad

1. From the BOP-2 or IOP-2 menu, navigate to EXTRAS → PARAMETER SAVE → RAM TO ROM.
2. Confirm by pressing OK. The panel will write the entire RAM image to flash.
3. After completion, read P10. If the wizard had been finished but the save had been missed, P10 will now show 0 and the drive is ready.
4. If P10 still shows 1, return to path A and finish the wizard manually.

6.3 Path C — Re-run Quick Commissioning From Scratch

1. Reset P10 = 1 deliberately to re-enter the wizard.
2. Set motor nameplate parameters: P304 (line voltage), P305 (motor rated current), P307 (motor rated power), P308 (cosφ), P309 (motor efficiency class), P310 (motor frequency), P311 (motor rated speed), P335 (motor cooling method).
3. Confirm encoder parameters if an encoder is present (P400, P408, P423).
4. Confirm ramp times (P1120, P1121) and command source (P700, P1000).
5. Set P1910 = 1 (or 2 with P1925 = 1 if you permit rotation).
6. Set P10 = 0 to close the wizard.
7. Save with P971 = 1.
8. Issue the first ON command. The drive will perform the static motor identification (audible clicking for 5–30 s depending on motor size) and then release control.

7. Verification

After applying the resolution, verify the drive is healthy before handing it back to operations.

1. Power-cycle the control unit. RDY LED must come on solid green within 5 s.
2. Read back P10 via BOP-2 or PROFINET; it must show 0.
3. Read back P1910; it should show 0 if identification has already completed, or the value it was set to if identification is intentionally pending.
4. Issue a slow speed setpoint (e.g. 5 % of rated) via the fieldbus or terminal and confirm ZSW1 bit 2 (Operation enabled) sets to 1.
5. Confirm the alarm buffer is empty (no A07980, A07981, A07991 entries).
6. Run a controlled ramp-up to rated speed with the load connected. Monitor r0027 (output current) and r0021 (DC-link voltage) for stability over 60 s.
7. Document the firmware version (r0018), the parameter checksum (r9782[0]) and the commissioning date in your asset record so that future operators know the drive is commissioned.

8. Prevention & Hardening

Several operational practices eliminate this failure mode from recurring.

• Mandate RAM-to-ROM after every commissioning session. Train operators to treat the BOP-2 RAM → ROM menu item as a mandatory sign-off step, not an optional save.
• Use the SD card option. The CU240-PN supports an SD card (6SL3254-0AM00-0AA0). Writing the parameter set to the SD card provides a redundant copy and a known-good boot image if the internal flash becomes corrupted.
• Lock P3 = 1 in production. Once the drive is commissioned and running, lower P3 to 1 (Standard). Operators will then no longer be able to enter the wizard accidentally from the keypad.
• PLC logic discipline. If a Siemens S7-1500/S7-1200 PLC is controlling the drive over PROFINET, the HMI must not send a "Reset to factory" or "Re-commission" command without explicit operator confirmation. Add an interlock in the safety-related portion of the PLC to block STW1 bit 0 (ON) when r3998 = 1.
• Alarm discipline. Map alarms A07980, A07981, and A07991 to the HMI so operators see why the drive is refusing to start, instead of guessing based on the LED pattern.
• Firmware consistency. Keep all G120 control units on the same firmware version where possible; mixed firmware versions can produce commissioning-state differences across the fleet. The SINAMICS G120 firmware V4.7 SP13 (and later) release notes contain the official list of resolved commissioning-state bugs.

9. Related Fault and Alarm Codes

10. Field-Commissioning Notes

The CU240-PN firmware revision matters. In firmware V4.5 and earlier, a power-cycle executed during the identification substate will not only revert P10 to 1 and P1910 to 1 but can also leave a phantom identification in progress latch that prevents the next P1910 from running until a factory reset is performed. Firmware V4.7 SP6 and later patches this by writing the commissioning state to a non-volatile flag that survives a power-cycle, but the standard recovery (P3 = 4, P10 = 0, P971 = 1) still applies.

When commissioning a fleet of G120 drives, capture r9782[0] (parameter checksum) immediately after the first successful commissioning session. A drifting checksum on subsequent reboots is a strong indicator that an operator has been writing parameters and saving them inconsistently, which in turn drives the failure mode described in this article.

11. Glossary

• RDY LED: Bi-color LED on the front of the CU240-PN that indicates converter state. Solid green = ready, flashing green 1 Hz = commissioning, solid red = fault.
• RAM-to-ROM: Action of copying the volatile parameter image into the non-volatile flash of the control unit.
• Quick Commissioning: The minimum parameter set required to put the drive into service; it covers motor nameplate, command source, setpoint source, and ramps.
• Static motor identification: A routine in which the drive applies voltage pulses to a stationary motor to measure stator resistance and leakage reactance.
• PROFINET IO: Industrial Ethernet-based fieldbus used by the CU240-PN for cyclic process data exchange.