Code SP0043: Position coder signal for differential speed mode disconnected
Issue Description & Safety Warning
The Fanuc Alpha-i Servo Spindle Amplifier has triggered a critical Position coder signal for differential speed mode disconnected 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
Amplifier LED display: 43 Also shown as: SP0043 (15i), SP9043 (30i/31i/32i), SP9043 (0i-D) Cause: The position coder signal of the master spindle used in differential spindle speed control is disconnected. For troubleshooting when this alarm is issued, see the subsection about alarm code 27.
Source: Fanuc αi Servo/Spindle Amplifier Maintenance Manual (B-65285EN/04) — Part II Troubleshooting
Last reviewed: 2026-07-01 · Verified against the manufacturer’s official documentation.
About Fanuc Alpha-i Servo Spindle Amplifier Alarms
Fanuc controllers include extensive self-diagnostics that flag or halt the machine when a fault is detected. Error code SP0043 on the Alpha-i Servo Spindle Amplifier identifies one specific fault condition — its documented cause and the official corrective steps are listed above, sourced from Fanuc's service documentation. Always confirm against the manual for your exact machine configuration and follow LOTO procedures before servicing.
Complete Alarm List: 135 Fanuc Alpha-i Servo Spindle Amplifier codes.
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