Code bUS (Fault): Option Communication Error
Issue Description & Safety Warning
The Yaskawa A1000 AC Drive has triggered a critical Option Communication 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: Fault Manual section: Yaskawa A1000 Troubleshooting No signal received from the PLC. - Check for faulty wiring. - Correct the wiring. - Check for disconnected cables and short circuits. Repair as needed. Faulty communications wiring or a short circuit exists. A communications data error occurred due to noise. - Check the various options available to minimize the effects of noise. - Take steps to counteract noise in the control circuit, main circuit, and ground wiring. - Ensure that other equipment such as switches or relays do not cause noise. Use surge suppressors if necessary. - Use only recommended cables or other shielded line. Ground the shield on the controller side or on the drive input power side. - Separate all communication wiring from drive power lines. Install an EMC noise filter to the drive power supply input. The option card is damaged. - Replace the option card if there are no problems with the wiring and the error continues to occur. The option card is not properly connected to the drive. - The connector pins on the option card are not properly lined up with the connector pins on the drive. - Reinstall the option card.
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 bUS (Fault) 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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