Troubleshooting SINAMICS G120C Faults F01659, A01699, A07409

Overview

The SINAMICS G120C is a compact, modular frequency converter in the SINAMICS family designed for machine builders who require an economic, space-saving, easy-to-operate drive with a power range typically from 0.55 kW to 132 kW (depending on frame size FSA through FSF) and line voltages of 3AC 200–240 V or 3AC 380–480 V. During initial commissioning via the IOP (Intelligent Operator Panel) or BOP-2 (Basic Operator Panel), three distinct diagnostic messages can appear: the safety-integrated fault F01659, the safety test alarm A01699 (F), and the V/f current-limit alarm A07409 (N). This reference consolidates the official meanings from the G120C List Manual and Operating Instructions, explains the underlying causes, and walks through a complete quick-commissioning sequence so that the drive can be cleared of these events and started reliably.

All fault and alarm descriptions in this article are taken from the official Siemens documentation set for the SINAMICS G120C (firmware V4.7 SP10 and later as listed in the current parameter manuals). Operators must observe the safety notices in the G120C Operating Instructions and the supplementary SINAMICS Safety Integrated Function Manual.

Fault and Alarm Identification Table

The letters in parentheses are part of the Siemens message-classification scheme: (F) marks an alarm that will become a fault if the drive does not see the expected feedback within a defined time; (N) is a pure informational alarm with no automatic escalation.

F01659 — SI P1 (CU): Write Request for Parameter Rejected

Behaviour. F01659 is a Safety-Integrated fault originating on the Control Unit (CU) of the SINAMICS G120C. When triggered, the drive executes the configured stop response (typically OFF2 with subsequent pulse disable) and latches. Until the cause is removed and the fault is acknowledged, no further parameter changes will be accepted on the safety-related parameter set.

Root causes. The official fault text means that a write request to a Safety-Integrated parameter (any parameter beginning with p96xx, p97xx, p98xx, or safety-relevant subset of r96xx) was attempted while one of the following conditions was true:

1. Safety functions (STO, SS1, SLS, SDI, depending on CU variant) were previously enabled and remain in an active or commissioned state.
2. The drive is in a state where safety parameterization is locked (e.g., during active STO test stop, or when the Safety commissioning mode p0010 = 95 is not selected).
3. An attempt was made to change a safety parameter while the drive was running or while pulses were enabled.
4. A CRC error exists in the safety parameter set; the firmware refuses to overwrite a corrupt signature.

In the most common commissioning scenario reported in the field, F01659 appears because the drive was previously configured with Safety Integrated enabled (for example, from a prior application) and the user then attempts to commission in non-safety mode. The internal safety parameter image is non-default, so the simple Factory Reset on the standard parameter set is insufficient; the safety parameter set must also be reset.

A01699 (F) — SI P1 (CU): Test Stop for STO Required

Behaviour. The drive is signalling that a mandatory test stop of the Safe Torque Off (STO) function is due. The function has not been forcibly disabled; pulses remain enabled. If the test stop is not performed and acknowledged within the configured monitoring time (default 8760 hours, i.e., approximately one year, configured via p9659), the alarm escalates to fault F01600.

Root causes.

• The drive is being commissioned for the first time after a long storage interval.
• The safety clock has reached p9659 hours since the last acknowledged test stop.
• The CU was replaced and the safety clock restarted without performing a test stop.

Resolution. The test stop must be executed manually: disable the STO input (24 V removed), verify that the drive's pulses have actually been cancelled (read r9771 bit status), then re-enable STO. The alarm is acknowledged by writing to p3981 (acknowledge safety fault) or by switching the drive off and back on.

A07409 (N) — Drive: U/f Control, Current Limiting Controller Active

Behaviour. The I_max controller (current-limit controller) inside the V/f or FCC control structure has become active. The drive is automatically reducing its output frequency to keep the motor current below the configured limit (p0640 = Imax motor / drive rated current by default, or p0305 × configurable factor). The alarm is informational only and does not change the stop reaction.

Root causes.

• Mechanical overload on the motor shaft.
• Ramp-up time (p1120) too short for the connected load inertia.
• Incorrect motor data; in particular, motor rated current p0305 is too low, causing the firmware to enforce an artificially tight current limit.
• Motor stalled during a load surge (e.g., product entering a conveyor at peak density).
• Voltage sag on the line side during the acceleration ramp.

A07409 alone does not require a parameter reset. It is a transient operating state, but if it appears consistently during the acceleration ramp the underlying mechanical or parameter issue must be resolved.

Quick Commissioning Prerequisites

Before any of the three faults above can be definitively cleared, the drive must be put into a known state through quick commissioning. The minimum prerequisites for a clean start on a SINAMICS G120C are:

• Hardware. Control Unit (CU240E-2 or CU240E-2 F, depending on whether safety is required) with PM240-2 Power Module. Motor with nameplate accessible. Line supply within the rated tolerance (±10 % of 380–480 V 3AC for FSA–FSF).
• Firmware. V4.7 SP10 or later for full G120C firmware set as shipped; verify via r0018 on the IOP.
• Operator panel. IOP (Intelligent Operator Panel, order number 6SL3255-0AA00-4JA0) or BOP-2 (Basic Operator Panel, 6SL3255-0AA00-4BA1). Alternatively, a PC with STARTER (legacy, V5.x) or Startdrive (TIA Portal V15.1 and later) connected via USB or PROFINET.
• Tools. Insulated torque screwdriver for power terminals (observe torque table from the Operating Instructions), and a digital multimeter for DC-link and 24 V verification.
• Documentation. The G120C Operating Instructions (French edition, BA7), the G120C List Manual, and the SINAMICS Safety Integrated Function Manual.

Step-by-Step Commissioning Procedure (IOP / BOP-2)

The following sequence resolves all three messages in the order they typically appear. The values shown correspond to a typical European 4-pole asynchronous induction motor (400 V / 50 Hz / 8.8 A / 4 kW / 1455 min⁻¹).

1. Restore factory settings. From the IOP home screen, navigate to Menu → Commissioning → Factory Reset. Select Safety parameter set → Reset as well as the standard parameter set. Confirm with OK. Wait until the drive displays Ready to switch on (status word bit 0 set).
2. Set access level. Set p0003 = 3 (Expert access). Without this, many safety and motor parameters are read-only and writes will be rejected with F01659. This is the parameter that resolves the "no write" symptom directly when starting from a previously commissioned drive.
3. Enter commissioning mode. Set p0010 = 1 (Quick commissioning). The drive will now accept the motor parameter block.
4. Line frequency standard. p0100 = 0 (Europe, 50 Hz, kW units). For North America use p0100 = 1 (60 Hz, hp units).
5. Motor rated voltage. p0304 = 400 V (line-to-line). On the IOP SETUP wizard this appears as Mot Volt.
6. Motor rated current. p0305 = 8.80 A (must match the motor nameplate exactly; otherwise the I_max controller in A07409 will activate unnecessarily).
7. Motor rated power. p0307 = 4.00 kW.
8. Motor rated power factor / cos φ. p0308 = 0.85 (typical for a 4-pole 4 kW motor). If the nameplate does not show cos φ, calculate cos φ = P / (√3 × V × I) from the other three values and enter the calculated number.
9. Motor rated frequency. p0310 = 50 Hz.
10. Motor rated speed. p0311 = 1455 min⁻¹. The slip (50 Hz nominal minus rated speed) is used by the firmware to compute the motor model.
11. Control mode. p1300 = 0 (linear V/f) for a simple application; for higher dynamic requirements select p1300 = 1 (FCC — flux-current control) or p1300 = 20 (sensorless vector, available from firmware V4.7).
12. Command source. p0700 = 2 (BOP/IOP) if starting from the panel; for terminal control use p0700 = 1 and configure the digital inputs through p0701–p0704.
13. Setpoint source. p1000 = 1 (motor potentiometer / MOP) for keypad control, or p1000 = 2 for analog setpoint, or p1000 = 6 for fieldbus setpoint.
14. Minimum and maximum frequency. p1080 = 0.00 Hz (corresponds to Min RPM = 0000 on the IOP) and p1082 = 50.00 Hz (motor rated frequency).
15. Ramp times. p1120 = 5.00 s (ramp-up) and p1121 = 5.00 s (ramp-down). For high-inertia loads increase p1120 to 10–15 s to avoid the I_max controller.
16. Digital input configuration. p0701 = 1 (DI0 = ON/OFF1) for a 2-wire control macro. The user in the original scenario used "2WIRE2" which corresponds to p0701 = 2 (ON/OFF1 with reversal of direction via DI1).
17. Motor identification. p1900 = 2 (rotating measurement) or, if the motor cannot be uncoupled, p1900 = 1 (static measurement). The measurement runs the next time the drive receives an ON command; expect 30–90 s for a 4 kW motor.
18. Close commissioning mode. Set p0010 = 0. The drive exits commissioning mode and computes internal motor model parameters (e.g., r0382, r0384).

Resetting the Safety Parameter Set

To clear F01659 permanently when safety functions had been activated in a previous application:

1. Bring the drive to the "Ready to switch on" state (no ON command, no safety input active).
2. Set p0010 = 95 (Safety Integrated commissioning). The drive now permits writes to safety parameters.
3. Reset the safety password if one has been set: p9761 = 0.
4. Restore safety to factory defaults: p9761 = 0 followed by setting the safety password to default and then perform Copy RAM to ROM (p0971 = 1).
5. Power-cycle the drive (24 V off, wait 30 s, 24 V back on). On boot, the safety parameter set will be CRC-checked against the new values; F01659 should not return.
6. If the drive is intended to be used without safety functions at all, no further action is required; the safety inputs are ignored.

If the application requires safety, perform the full Safety Integrated commissioning in p0010 = 95 per the Safety Integrated Function Manual, accept the safety password, and configure the STO source via p9620 (PROFIsafe) or p9621 (terminal) accordingly.

Clearing A01699 — STO Test Stop

1. With the drive in "Ready to switch on", confirm that the motor can be safely uncoupled or that the mechanical system tolerates a pulse-cancel event.
2. Remove the 24 V signal from the configured STO source. For terminals, open the wiring on the STO+/STO− pair at the CU; for PROFIsafe, command STO via the controller.
3. Verify the response: r9771.0 (status STO active) should read 1 within 5 ms, and r9773.0 (STO acceptance test required) should be 0 immediately after the test.
4. Re-apply the 24 V signal. r9771.0 must return to 0 within the configured tolerance.
5. Acknowledge via p3981 = 1 (Acknowledge safety fault / reset Safety Integrated fault buffer), or power-cycle the drive. The r9781 (Safety Integrated operating hours counter for test stop) is now updated.

Verifying the Drive Starts Correctly

After clearing the three messages, perform the following verification sequence before placing the drive in production:

1. Check the fault buffer: r0945[0] should show no entry; r2122[0] should show no active alarm.
2. Press the green ON key on the IOP. The status should transition Ready to switch on → Switched on → Operation enabled.
3. Observe r0021 (motor speed actual) on the IOP; it should track the setpoint ramp within 200 ms of the ramp time.
4. Use the MOP (motor potentiometer) keys on the IOP to ramp from 0 to 50 Hz in steps. The motor should accelerate smoothly. If A07409 returns, the ramp time is too short for the load or the motor rated current is under-entered.
5. Press the red OFF key. The drive should ramp down per p1121 and stop.
6. Save the parameter set to the CU's non-volatile memory: p0971 = 1 or Menu → Commissioning → Save RAM to ROM on the IOP. Wait for the IOP to display Save successful. A power loss before this step discards all changes.

Parameter Reference — Frequently Used Values

Troubleshooting Matrix

Dimensional Reference for Motor Data Verification

When the nameplate is partially illegible, verify the consistency of the entered motor data against the three-phase apparent power formula:

S = √3 × V_LL × I / 1000 [kVA]

For the 4 kW 400 V 8.8 A motor used as an example: S = √3 × 400 × 8.8 / 1000 = 6.10 kVA. The power factor from the nameplate should then satisfy cos φ = P / S = 4.00 / 6.10 = 0.66 (rounded to 0.65–0.85 depending on motor efficiency class IE1–IE3). If the entered combination of p0304, p0305, p0307, and p0308 yields a cos φ outside 0.5–1.0, the firmware will flag a data inconsistency (alarm A07910–A07922 depending on which field is wrong). Always re-check the cos φ value after a substitution.

Edge Cases and Field-Proven Caveats

• STO wired but unused. If the application does not need safety but the CU variant has STO terminals (e.g., CU240E-2 F), the inputs must still be jumpered to 24 V. An open STO input holds the drive in STO state and explains the "setpoint displayed, drive does not start" symptom. Always install the factory yellow jumper on STO+ / STO− if safety is not in use.
• BOP-2 vs IOP behaviour. The BOP-2 does not present the SETUP wizard; it requires manual parameter entry through p0003 = 3, p0010 = 1, then each motor parameter in turn. With BOP-2 the wizard will not auto-skip past safety commissioning, so F01659 will be visible earlier.
• Fieldbus controller missing. If the application uses a PROFINET or PROFIBUS controller as the command source but the bus has not been activated in p0015 = 12 or p0922, the drive will display "setpoint = -0.9 t/min" because no control word is arriving. Verify the bus LEDs on the CU and the GSD file version.
• Save before power-off. RAM-to-ROM copy (p0971 = 1) is mandatory after any parameter change that needs to survive a power cycle. The IOP auto-prompts for this at the end of the SETUP wizard but only if the user completes the wizard through Save & Exit.
• Motor identification in p1900 = 2. The rotating measurement accelerates the motor up to the maximum frequency set in p1082. If the load cannot tolerate overspeed (e.g., fan blades rated below 50 Hz), cap p1082 to the application maximum before enabling rotating measurement.
• Multiple-parameter writes from PC tool. When commissioning via Startdrive or STARTER, bulk parameter downloads will only succeed if p0003 ≥ 2 and the drive is in the correct state. F01659 during a STARTER download indicates the safety image is non-default; do not bypass the warning.

Field Commissioning Procedure Summary

1. Wire STO jumpers, motor, line, and operator panel. Verify with multimeter: line voltage within ±10 %, motor insulation resistance > 1 MΩ at 500 V.
2. Power up the CU only (24 V). Read firmware version on the IOP. Note any active fault or alarm. If F01659 is present, go to the "Resetting the Safety Parameter Set" section first.
3. Restore factory settings (standard + safety) and confirm Ready to switch on.
4. Set p0003 = 3, p0010 = 1, then enter the ten motor data parameters from the nameplate.
5. Configure control source (p0700), setpoint source (p1000), ramp times (p1120, p1121), and min/max frequency.
6. Set p1900 = 2 (rotating identification) only if the motor can run uncoupled or under light load.
7. Set p0010 = 0. Save parameters via p0971 = 1. Power-cycle the CU.
8. Apply the ON command. Monitor r0021, r0027, and the alarm buffer.
9. If A01699 returns after the first start, perform the STO test stop and acknowledge with p3981 = 1.
10. If A07409 returns during acceleration, increase p1120 or verify p0305 against the nameplate.

Related Diagnostic Resources

• Fault buffer: r0945[0..7] lists the active and historical faults with values.
• Alarm buffer: r2122[0..7] lists the active and historical alarms.
• Status word 1: r0054[0..15] provides the drive state machine bits; a "Ready to switch on" drive should show bit 0 = 1, bit 1 = 0, bit 2 = 0, bit 3 = 0, bit 4 = 0, bit 5 = 0, bit 6 = 0.
• Status word 2: r0055 provides additional bits including the drive running flag.