PLCs troubleshooting answers

The TwinCAT NC Error 0x4550 (17744) indicates that the position lag error exceeded the Maximum Position Lag Value for longer than the Maximum Position Lag Filter Time. This fault typically occurs during acceleration, at …

The TwinCAT NC Error 0x4260 (16992) indicates that the controller enable for an axis or coupled slave axis is not present. This can occur if the controller enable is withdrawn during active positioning or if a move is in…

An EtherCAT slave stuck in the INIT state means it hasn't established basic communication or its identity doesn't match the configuration. This often happens after activating a new configuration or restarting TwinCAT. Th…

A Working Counter (WcState) error of 1 indicates invalid real-time communication for an EtherCAT slave. This means the master received an unexpected working counter value from a datagram, leading it to discard all input …

The EtherCAT AL Status 0x0030 fault, "Invalid DC SYNC Configuration," indicates that the distributed clock configuration is invalid for the application. This typically occurs during startup transitions (PREOP to SAFEOP o…

An EtherCAT slave reporting AL Status 0x0024 indicates an invalid input mapping, meaning the process data configuration (PDOs) in the TwinCAT 3 project does not match what the slave expects. This typically occurs during …

AL Status 0x001E indicates an invalid input configuration, specifically for the SyncManager handling input process data. This fault typically occurs during EtherCAT startup when transitioning from PREOP to SAFEOP, often …

The EtherCAT AL Status 0x001D indicates an invalid SyncManager configuration for output process data. This fault typically occurs during the transition from PREOP to SAFEOP at EtherCAT startup, or after a device replacem…

The EtherCAT AL Status 0x001B Sync Manager Watchdog fault indicates that a slave did not receive process data within the specified watchdog time, typically 100 ms. This usually occurs when cyclic process data stops, ofte…

The EtherCAT AL Status 0x001A Synchronization Error indicates that process data or synchronization events are arriving too late or out of step, causing the slave to return to SAFEOP. This fault is often seen in OP mode o…

The EtherCAT AL Status 0x0011 indicates an invalid requested state change, meaning the EtherCAT State Machine (ESM) refused a transition. This often happens during EtherCAT startup or when manually changing states in the…

An ADS 1861 (0x745) timeout indicates that a request was sent to a remote terminal, but no response was received within the specified ADS timeout period. This often points to an issue with the remote terminal's configura…

ADS Error 1808 (0x710) indicates that the PLC runtime could not find a symbol name requested by a client (like an HMI or SCADA). This often occurs after a PLC download, especially if variables were renamed or removed. Th…

ADS Error 1798 (0x706), also known as ADSERR_DEVICE_INVALIDDATA, indicates that the server received a request with the correct size but rejected its content because the data values were invalid. This typically occurs dur…

TwinCAT ADS Error 1797 (0x705), also known as ADSERR_DEVICE_INVALIDSIZE, indicates that the data length sent by an ADS client (like an HMI or SCADA) does not match the size expected by the TwinCAT server for a specific s…

ADS Error 1793 (0x701) indicates that the addressed ADS device received a request but does not support the specific command or index group. This differs from other ADS errors like 1794/1795, where the service exists but …

ADS Error 18 (0x12) indicates that a port is disabled because the TwinCAT system service is not running. This typically occurs right after a PC boot or if the TwinCAT runtime has stopped or failed to start. The error mea…

ADS Error 7 (0x7) indicates that the local ADS router on your client machine (engineering PC or HMI) cannot find a route to the target's AMS NetId. This means the connection request never leaves your client. This often h…

ADS Error 6 (0x6, ERR_TARGETPORTNOTFOUND) indicates that while the route to the target machine is functional, no ADS server is listening on the specific AMS port the client is trying to address. This often occurs after a…

An OB122 I/O access error on a Siemens S7-1500 CPU indicates a problem during direct access to I/O data, such as reading from an input module. The CPU will remain in RUN and log a diagnostics buffer entry. A 16#42 fault …

An S7-1500 CPU in STOP mode with OB121 and Fault_ID 16#3A indicates a programming error, specifically an attempt to access a data block (DB), function (FC), or function block (FB) that is either not loaded or does not ex…

An OB86 Rack Error on a Siemens S7-1500 indicates a failure or return of a DP master system, PROFINET IO system, DP slave, or IO device. Unlike S7-300/400, the S7-1500 CPU defaults to staying in RUN mode if OB86 is not c…

An OB82 diagnostic interrupt on a Siemens S7-1500 CPU indicates a change in a diagnostics-capable module's status, a power supply/battery backup error, or a memory error. Unlike older S7 models, the S7-1500 CPU remains i…

An OB80 Time Error on a Siemens S7-1500 CPU means the cyclic program or an interrupt OB ran longer than the maximum configured cycle time. While the CPU continues after the first overrun with OB80 present, a second overr…

A Major Fault T07:C42 on a ControlLogix controller indicates a revision mismatch. This means the project in the controller's nonvolatile memory has a different firmware revision than the controller itself. This fault typ…

A Major Fault T07:C41 indicates a 'Load Type Mismatch' where the controller failed to load from nonvolatile memory because the project on the memory card was saved for a different controller type. This typically occurs a…

A Type 7 Code 40 fault on a ControlLogix controller indicates that storing the project to the nonvolatile memory card failed. This can occur during a project store operation or after a download with the store-to-nonvolat…

A Type 6 Code 1 fault, or Watchdog fault, indicates that a user task did not complete within its allotted watchdog time. This often occurs after program changes that introduce new logic or loops, causing the task to take…

A T04:C83 'Value Out of Range' major fault on a ControlLogix or CompactLogix controller indicates that a data value tested was outside its required limits. This specific fault type is associated with array subscripts use…

A Major Fault T04:C34, also known as a 'Negative Timer' fault, indicates that a timer instruction in the Logix 5000 controller program received a negative value for its preset (.PRE) or accumulated value (.ACC). This fau…

A ControlLogix or CompactLogix controller displays a Major Fault Type 4 Code 31 when a JSR instruction attempts to call a subroutine (SBR/RET) with fewer parameters than the subroutine expects. This fault occurs when the…

A ControlLogix or CompactLogix controller displaying a Major Fault T04:C20 indicates a program fault where an array subscript was too large for the array, or the .POS or .LEN value of a CONTROL structure was invalid. Thi…

A Major Fault T04:C16, or 'Unknown Instruction', indicates the controller encountered an instruction it doesn't recognize during program execution. This typically happens after a program download, especially if the proje…

A T03:C23 fault on a Logix 5000 controller indicates that a required I/O module connection was not established before the controller entered Run mode, within its configured time limit. This often occurs during the transi…

A T03:C16 major fault on a Logix 5000 controller indicates that a connection to a required I/O module has failed while the controller was in Run mode. This fault occurs only if the module is configured to cause a major f…

A Type 1 Code 1 (T01:C01) fault on a ControlLogix controller indicates that the controller powered up in Run or Remote Run mode after a power loss. This fault prevents the controller from automatically returning to norma…