Code Er-21: Z Pulse Correction Error
Issue Description & Safety Warning
The Yaskawa A1000 AC Drive has triggered a critical Z Pulse Correction Error alarm. Immediate attention from a qualified operator or maintenance technician is required to prevent secondary damage to the equipment or spoiled parts during the manufacturing cycle. Always ensure standard safety and LOTO procedures are followed before accessing electrical cabinets.
Official Troubleshooting Steps
Code type: Auto-tuning fault/alarm Manual section: Yaskawa A1000 Troubleshooting Motor was coasting when Auto-Tuning was performed. Make sure the motor has stopped completely. Repeat Auto-Tuning. Either the motor or the PG encoder on the motor is not properly wired. Check the wiring for the motor and the PG encoder. Repeat Auto-Tuning. The direction for the PG encoder is set incorrectly, or the number of pulses set for the PG encoder is wrong. Check the direction and number of pulses set for the PG encoder. Repeat Auto-Tuning. PG encoder is damaged. Check the signal output from the PG encoder attached to the motor. Replace the PG if damaged. Motor inertia is large. Increase the setting of n8-02 (Pole Attraction Current). Z-Pulse Offset Tuning was performed when b1-04 was set to 1. - Z-Pulse Offset Tuning cannot be performed for a machine in which reverse operation is prohibited. - If the machine allows reverse operation, set b1-04 to 0 to enable Reverse Operation Selection and then perform the Z-Pulse Offset Tuning. Motor vibrates during tuning. - Increase the setting of n8-03, Current Startup Time, and n8-04, Pole Attraction Time. - Decrease the setting of n8-02, Pole Attraction Current.
Source: Yaskawa AC Drive A1000 High Performance Vector Control Drive Technical Manual (SIEP C710616 21H)
Last reviewed: 2026-07-01 · Verified against the manufacturer’s official documentation.
About Yaskawa A1000 AC Drive Alarms
Yaskawa controllers include extensive self-diagnostics that flag or halt the machine when a fault is detected. Error code Er-21 on the A1000 AC Drive identifies one specific fault condition — its documented cause and the official corrective steps are listed above, sourced from Yaskawa's service documentation. Always confirm against the manual for your exact machine configuration and follow LOTO procedures before servicing.
Complete Alarm List: 280 Yaskawa A1000 AC Drive codes.
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