Resolving End Position Fault on SIMOCODE pro V Positioner 1

The SIMOCODE pro V motor management and control device (basic unit 3UF7010-, 3UF7011-, 3UF7013-, 3UF7020-, 3UF7021-, 3UF7023-series with firmware V15.x or later in the positioner 1 operating mode) is widely used for the controlled switching and protection of motors driving actuators such as dampers, valves, and gate mechanisms. One of the more disruptive fault conditions operators encounter in the field is the recurring "Fault - End position" message, which trips the positioner off and—under default behavior—requires a power-down reset at the device. In a DCS-integrated plant, this is rarely acceptable: an operator must be able to acknowledge the fault remotely from the control room. This reference details the trigger conditions, root causes, acknowledgment paths, and remote-reset strategies for end position faults on SIMOCODE pro V configured as positioner 1.

1. Positioner 1 Operating Mode: Functional Overview

Positioner 1 in SIMOCODE pro V manages a single actuator with the following I/O and logic structure:

• Control commands (outputs): OPEN (Q1, configurable) and CLOSE (Q2, configurable), driven by the controlling PLC/DCS via SIMOCODE pro V's fieldbus interface (PROFINET, PROFIBUS DP, or Modbus TCP depending on the basic unit variant).
• Feedback signals (inputs): Two digital feedback contacts reporting the actuator's mechanical end positions—End position OPEN reached and End position CLOSED reached. These can be wired to onboard inputs (e.g., IN1, IN2) or to inputs on a digital module (DM-F, DM).
• Torque/limit feedback (optional): For actuators equipped with torque switches, torque OPEN and torque CLOSED signals can be wired and evaluated.
• Monitoring timers: Max. running time (the time the actuator is allowed to travel from one end position to the other before a Running time exceeded fault is raised) and the implicit end position plausibility check that raises the end position fault.

Per the official SIMOCODE pro Parameterization Operating Manual (entry ID 109743958), the positioner continuously compares the issued control command with the resulting end-position feedback. When a control command is issued but the matching end position is not reached within the configured monitoring window—or when a feedback signal is received that contradicts the issued command—the device trips with the fault message "Fault - End position" and removes the drive command, opening the contactor outputs.

2. Fault Definition: "Fault - End Position"

The end position fault is one of the positioner-specific diagnostics defined in the SIMOCODE pro V fault catalog. Its properties:

3. Trigger Conditions

The end position fault is generated when one of the following conditions is detected by the positioner state machine:

1. Missing feedback after control command: An OPEN command is issued but the End position OPEN feedback contact does not close within the Max. running time window (typical default: 30 s, configurable 1–255 s in parameter P_max_running_time_positioner).
2. Plausibility contradiction: Both end-position feedback signals are simultaneously high (interlocked contacts failing or both limit switches actuated), or the active feedback does not correspond to the last issued command.
3. Pulse-width conflict: The control command is shorter than the actuator's mechanical response time, causing the feedback to never settle in the commanded state. This is the most common field cause in DCS-driven damper loops with short pulse-width-modulated (PWM) PID output.
4. Wiring or contactor failure: Loss of feedback due to broken wire, contactor auxiliary not pulling in, or feedback contact mechanically stuck.
5. Mechanical jam: The actuator is physically unable to reach the commanded end position within the running time window.

4. Root Cause Analysis

When the fault reappears repeatedly after power cycling, the root cause is almost always one of the following:

4.1 DCS Output Pulse Too Short

Discrete PID controllers in DCS systems (PCS 7, SIMATIC, third-party) commonly generate pulse-width outputs on a relay or 24 V DO card. If the pulse width is shorter than the actuator's startup delay (typically 200–800 ms for motorized dampers with gearbox), the motor contactor energizes but the actuator never moves far enough to leave the previous end position feedback state. SIMOCODE pro V detects the mismatch and latches the fault.

4.2 Feedback Contact Wiring or Logic Inversion

The end-position feedback inputs on the basic unit (e.g., IN1) can be configured as NO or NC. If the wiring matches NO but the contact is wired NC (or vice versa), the positioner sees a constant "open" feedback and faults as soon as a CLOSE command is issued.

4.3 Running Time Window Set Too Tight

The default P_max_running_time_positioner (parameter block Positioner, address typically shown as parameter "Max. runtime positioner" in SIMOCODE ES (TIA Portal)) is 30 s. For larger actuators with long stroke times (60–120 s), this triggers spurious end-position faults.

4.4 Reset Class Set to "Manual Reset"

By factory default, the end-position fault is assigned to reset class Manual RESET (power cycle required). This is the most common reason operators perceive the fault as "requiring power-down reset." The remedy is to reclassify the fault to a bus-resettable class.

5. Acknowledgment Methods

The SIMOCODE pro V supports four independent reset paths for the end position fault:

5.1 Counter-Command Acknowledgment (Recommended)

The cleanest acknowledgment is to issue the counter command from the DCS. The positioner state machine in SIMOCODE pro V is built on this principle: a fault latched in the OPEN direction is cleared by a valid CLOSE command reaching the CLOSED end position feedback, and vice versa. This is documented in the operating manual's "Positioner fault – End position" section.

Implementation in the DCS logic (structured text example for an S7-1500 / TIA Portal block driving SIMOCODE pro V over PROFINET):

// SIMOCODE pro V Positioner 1 control word (bits mapped to PROFINET slot 0)
// Bit 0 = OPEN command, Bit 1 = CLOSE command, Bit 7 = Fault reset

IF "Fault_end_position" THEN
    // Issue counter command to acknowledge
    IF "Last_command" = OPEN THEN
        "Cmd_CLOSE" := TRUE;
        "Cmd_OPEN" := FALSE;
    ELSE
        "Cmd_OPEN" := TRUE;
        "Cmd_CLOSE" := FALSE;
    END_IF;
END_IF;

// Pulse extend: hold counter command until new end position feedback is confirmed
TON_Pulse_extend(
    IN := "Cmd_OPEN" OR "Cmd_CLOSE",
    PT := T#2s // extend minimum 2 s for actuator mechanical response
);

"Cmd_valid" := "Cmd_OPEN" OR "Cmd_CLOSE";
"Reset_bit" := "HMI_reset_button" AND NOT "Fault_active";

5.2 Remote Bus Reset via PROFINET Control Word

For a true single-button HMI reset, configure the end-position fault to a bus-resettable class in SIMOCODE ES:

1. Open the device project in SIMOCODE ES (TIA Portal) V15.1 or later.
2. Navigate to Parameters > Faults > Positioner > End position fault.
3. Set Reset to Manual RESET with Remote acknowledgment allowed enabled (or to Automatic RESET if appropriate to the safety class of the actuator).
4. Compile and download the parameter set to the basic unit.
5. In the DCS, set the RESET bit in the cyclic control word for at least 100 ms (SIMOCODE pro V evaluates the rising edge).

6. Configuration Parameters Reference

The relevant parameters for positioner 1 end-position monitoring live in the SIMOCODE ES parameter tree under Positioner:

7. DCS Integration: Wiring Reset to the HMI

To wire a DCS HMI reset button to the SIMOCODE pro V end-position fault:

7.1 PROFINET Path

1. In the SIMATIC TIA Portal / PCS 7 project, map the SIMOCODE pro V as a PROFINET device with the GSDML file GSDML-Vx.x-Siemens-SIMOCODE-YYYYMMDD.xml supplied with the device.
2. Insert the "SIMOCODE pro V PN" device into the PROFINET topology.
3. Slot 0 contains the cyclic I/O. The control word is at output address QBx (1 byte); the status word is at input address IBx (1 byte).
4. Bit mapping (control word, byte 0):
   • Bit 0: OPEN command
   • Bit 1: CLOSE command
   • Bit 2: Stop command
   • Bit 7: Reset / Acknowledge
5. Status word (input, byte 0):
   • Bit 0: End position OPEN reached
   • Bit 1: End position CLOSED reached
   • Bit 7: Fault active
6. In the HMI, the "Reset SIMOCODE Fault" button sets bit 7 of the control word for 200 ms, then releases.

7.2 PROFIBUS DP Path

Identical structure to PROFINET, but using the PROFIBUS GSD file SIMOCODE.GSD. Cyclic I/O slots 0/1 contain the 1-byte control and status words; acyclic access via DPV1 read/write to records 0x0080 (Reset) and 0x0081 (Parameter) is also supported.

7.3 Modbus TCP Path

For SIMOCODE pro V with the Modbus TCP communication module (3UF7013-1AU00-0 or higher), the holding register layout is documented in the Modbus manual. The end-position fault acknowledgment is via holding register 4x0008 (Reset/ACK), coil-style bit operation.

8. Diagnostic Workflow

Use this field-proven sequence when the fault recurs after every reset:

1. Read the device log: In SIMOCODE ES, connect online and open Diagnostics > Event log. Filter on "Positioner / End position" to see the time-stamped sequence of commands and feedbacks.
2. Check the command duration: Compare the DCS pulse width against the actuator's measured startup time. If the pulse is < 500 ms for a typical damper, lengthen the output via a minimum-pulse-width function in the DCS.
3. Verify feedback wiring: With the actuator powered down, measure continuity on each end-position contact in both mechanical states (fully OPEN, fully CLOSED, mid-stroke). Confirm NO/NC matches the SIMOCODE ES input configuration.
4. Verify running time window: Time a manual stroke command and set Max. running time to 1.2 × measured full-stroke time.
5. Check for mechanical binding: Manually drive the actuator through its full stroke; listen for gearbox grinding or measure motor current against the nameplate FLA.
6. Reset class audit: Confirm the fault is in a class that allows bus reset. If not, reconfigure in SIMOCODE ES and download.
7. Test remote reset: From the DCS HMI, trigger the reset button and observe the fault word clear within 200 ms.

9. Verification

After applying the remote reset configuration and root-cause fix:

1. Issue an OPEN command from the DCS; confirm the actuator drives to fully open and the End position OPEN feedback bit sets.
2. Issue a CLOSE command; confirm full closure and the End position CLOSED feedback bit sets.
3. With the actuator in the fault state (simulate by disconnecting one feedback wire), verify the HMI reset button clears the fault without power cycling.
4. Confirm via SIMOCODE ES online diagnostics that no further "End position" events are recorded in the event log over a 24-hour burn-in period.
5. Confirm the DCS faceplate displays the correct fault text and the reset button is enabled only when the fault is active.

10. Common Pitfalls

• Reset class confusion: "Manual RESET" with remote acknowledgment is not the default. A power-cycle reset is required if the reset class is left at factory default. Always explicitly configure remote-acknowledgment permission.
• Pulse-width PID loops: A standard PID with proportional band tighter than the actuator dead time will produce oscillating short pulses. This is the most common field cause. Either add a dead band to the PID output, or implement a minimum ON/OFF time of 500 ms in the DCS output block.
• Both-feedbacks-high condition: If both limit switches are mechanically actuated at the same time (e.g., during a stalled actuator at the mechanical stop), SIMOCODE pro V treats this as a contradiction. Verify the actuator mechanical design allows one contact to open before the other closes.
• Feedback contact bounce: Mechanical limit switches can chatter at the end position. Enable input debounce in SIMOCODE ES (parameter P_input_debounce_time, default 10 ms; for noisy environments use 50–100 ms).
• Firmware version: Older SIMOCODE pro V basic units on firmware < V14.0 may not expose the remote-acknowledgeable reset class for the end-position fault. Verify firmware via the device's web server or SIMOCODE ES online > Device info.

11. Related Faults and Cross-References

For complete parameter definitions and the full fault catalog, refer to the official SIMOCODE pro parameterization operating manual (Siemens Entry ID 109743958) and the SIMOCODE pro V system manual (Entry ID 109743761) on Siemens Industry Online Support.