Code 9047: SPN_n_: POS–CODER SIGNAL ABNORMAL
Issue Description & Safety Warning
The Fanuc 16i/18i/21i CNC has triggered a critical SPN_n_: POS–CODER SIGNAL ABNORMAL 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
Replace the cable. Re–adjust the BZ sensor signal. Correct the cable layout (vicinity of the power line). The A/B phase signal of the spindle position coder (connector JY4) is abnormal. The A/B phase signal (connector JY2) of the MZ or BZ sensor is abnormal. The relationship between the A/B phase and 1–rotation signal is incorrect (Pulse interval mismatch).
Source: Fanuc Series 16i/18i/21i-B Operator's Manual, Appendix G Alarm List (B-63864EN/03)
Last reviewed: 2026-07-01 · Verified against the manufacturer’s official documentation.
About Fanuc 16i/18i/21i CNC Alarms
Fanuc controllers include extensive self-diagnostics that flag or halt the machine when a fault is detected. Error code 9047 on the 16i/18i/21i CNC 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: 360 Fanuc 16i/18i/21i CNC codes.
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