What causes Beckhoff TwinCAT 3 (XAR/XAE) with EtherCAT fault AL 0x001A?

1. Process data arriving too late or missing (lost frames, CRC errors, cabling): Read CRC and lost frame counters per port in the online view; check cabling, connectors and shielding per ETG.1600. 2. Task timing: real-time jitter or cycle overruns on the controller: Trace the exceed counter and task execution time in Scope View; check task priorities. 3. DC settings changed by hand (shift times, reference clock): Compare DC settings with the defaults and the device documentation.

EtherCAT AL Status 0x001A Synchronization Error: Causes

Beckhoff: if too many RxPDO toggle errors occur (the RxPDO Toggle Failed Counter exceeds the internal limit), the slave returns to SAFEOP + error with 0x001A; multiple synchronization errors, the device is not synchronized any more. It is used when the causes behind codes 0x2C, 0x2D, 0x32, 0x33 and 0x34 cannot be distinguished. Raised in OP or on S→O.

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Upload a keypad photo, the fault history or a parameter export from your Beckhoff TwinCAT 3 (XAR/XAE) with EtherCAT. InduQT compares the evidence and suggests the next useful checks.

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When it happens

In OP, after running for a while
On the transition SAFEOP to OP of DC-synchronized slaves (drives, fast I/O)

Likely causes and checks

1Process data arriving too late or missing (lost frames, CRC errors, cabling)

Points to it: LostFrames or CRC counters rising on the segment; DevState bit 12 "DC not in sync" may be set.
Check: Read CRC and lost frame counters per port in the online view; check cabling, connectors and shielding per ETG.1600.

2Task timing: real-time jitter or cycle overruns on the controller

Points to it: Task exceed counter increasing at the same times.
Check: Trace the exceed counter and task execution time in Scope View; check task priorities.

3DC settings changed by hand (shift times, reference clock)

Points to it: Problem started after a configuration change; Beckhoff warns manual DC settings can put SYNC pulses at the wrong time.
Check: Compare DC settings with the defaults and the device documentation.

Telling it apart

0x001B (sync manager watchdog) means no process data at all within the watchdog time; 0x001A means data or sync events arrived but too often late or out of step.
0x002C (fatal sync error) means the SYNC signal is no longer generated at all; Beckhoff: set the master to INIT and back to OP.

Relevant parameters

Parameter	Name	Why it matters
DC > SYNC Shift Time	Sync shift time (outputs/inputs)	Beckhoff: in case of sync problems, +10…20 % of cycle time for outputs, −10…20 % for inputs can be entered as a reference value; >100 % is not meaningful.

Evidence to collect

EtherCAT online tab screenshot (State, CRC counters per port, LostFrames)
Logger export with the AL status code and time
Scope View trace of WcState, DevState and the task exceed counter
DC settings of the slave (Advanced Settings > Distributed Clock)

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Beckhoff TwinCAT 3 (XAR/XAE) with EtherCAT fault AL 0x001A: Synchronization error