What causes FANUC alarm 354?

Encoder cable damaged, pinched, or connector loose at motor or amplifier end. Encoder disk contaminated with coolant or chips. Encoder backup battery depleted on absolute encoder systems. Encoder hardware failure — signal processing fault. Encoder supply voltage below specification.

How do I fix FANUC alarm 354?

1. Inspect encoder cable for damage and reseat connectors at both ends. 2. Check encoder backup battery voltage and replace if below 3V. 3. Clean the encoder disk and reading head if contamination is suspected. 4. Check encoder supply voltage at the connector. 5. Replace encoder cable first; replace encoder if cable checks out.

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FANUC Controller

Servo/Axis · Advanced · 30-90 minutes

Alarm 354

Fanuc Alarm 354 - Encoder Phase Mismatch

Alarm 354 occurs when a G28 (return to reference position) command is issued to the master axis during synchronous control operation (tandem, gantry, or coupled axis mode), but one or more slave axes have not completed their reference position return. The CNC system requires all axes in a synchronized group to have established reference positions before allowing G28 commands to the master axis.

FANUCServo/AxisAdvanced30-90 minutes

354

Fanuc Alarm 354 - Encoder Phase Mismatch

Pulse Coder Phase Error

Root Cause Summary

Alarm 354 occurs when a G28 (return to reference position) command is issued to the master axis during synchronous control operation (tandem, gantry, or coupled axis mode), but one or more slave axes have not completed their reference position return. The CNC system requires all axes in a synchronized group to have established reference positions before allowing G28 commands to the master axis.

Safety

Position feedback may be wrong

Causes and Fixes

1
Navigate to POSITION > ABSOLUTE screen and verify which axes display '***' or '?' indicating no reference position. Note the slave axis numbers in the synchronous group.
2
Check parameters 1815 (master axis number) and 1816 (slave axis number) to confirm the synchronous control axis configuration. For gantry systems, also verify parameters 1820-1827.
3
Perform manual reference position return on all slave axes first. In JOG mode, select each slave axis individually and press the +REF button to complete reference return sequence.
Ensure adequate clearance and verify zero return direction parameter 1006#0-3 is correctly set for each axis before executing reference return.
4
After slave axes show established reference position (no '***' on ABSOLUTE screen), verify synchronous mode is active via parameter 1801#3=1, then retry G28 command to master axis.

DIY Feasiblehigh confidence

Call a technician if:

·Encoder replacement required
·Servo amplifier failure confirmed
·Mechanical coupling repair needed

Prevention

Always establish reference positions on all axes before enabling synchronous control
Perform regular encoder signal quality checks
Maintain clean environment around encoder components

Common Mistakes

Attempting G28 on master axis while slave axis lacks reference
Ignoring intermittent encoder signal quality issues
Incorrect synchronous parameter configuration during setup

Related Alarms

401 414 435 736

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