What is an NCU error code?

NCU error codes are diagnostic codes displayed on the 7-segment display of Siemens SINUMERIK Numerical Control Units. These codes indicate system status, errors, or operational states of the CNC machine control system.

How do I find the error code on my NCU?

The error code is displayed on a 7-segment LED display located on the front of the NCU or CCU module. It shows a single hexadecimal character (0-9, A-F) and may include a decimal point that flashes or remains solid to indicate additional status information.

What is the difference between NCU and CCU?

NCU (Numerical Control Unit) is used in SINUMERIK 840D and 840D sl systems, while CCU (Compact Control Unit) is used in the 810D system. Both use the same diagnostic error codes and share the same diagnostic manual (6FC5297).

What should I do if I see an error code?

Enter the error code into this diagnostic tool to get the official meaning and troubleshooting steps. Follow the real-world fix recommendations, which may include checking connections, replacing components, or power cycling the system.

Decrypt Your Siemens NCU Error Codes

Enter the error code from your machine's 7-segment display to instantly decode what it means and get troubleshooting guidance.

Select System Type:

Current

SINUMERIK

840D / 840D sl / 810D Error Code Diagnostics

CNC machine control systems for machining centers, lathes, and multi-axis machines

Supported Control Units:

NCU 571.5NCU 572.5NCU 573.5CCU

Error Code Format:0-9, A-F (hexadecimal)

SINAMICS

S120 Fault Code & LED Diagnostics

Modular drive systems for servo and vector applications

Supported Control Units:

CU320-2 DPCU320-2 PNCU310-2 DPCU310-2 PN

Error Code Format:Fxxxxx (Fault) / Axxxxx (Alarm)

Input Controls

Pick the hex digit on your machine’s 7-segment display, then match the decimal dot.

Digit

0–9, A–F

Use the keypad or the small digit field. One hexadecimal character: 0–9 or A through F.

Dot Status

7-Segment Display

Start with the digit on your display

Enter one hexadecimal character (0–9, A–F) from the 7-segment display. Match the decimal dot (off, solid, or flashing) and choose NCU or CCU below. If RDY, SF, or DP1 LEDs indicate a fault, use the LED panel—those states can override the segment code.

Reference: Siemens SINUMERIK Diagnostics Manual (6FC5297).

Note: 3 supported models (840D, 840D sl, 810D) share the same diagnostic manual (6FC5297) and use compatible error codes.

Decrypt Your Siemens NCU Error Codes

Enter the error code from your machine's 7-segment display to instantly decode what it means and get troubleshooting guidance.

Select System Type:

Current

SINUMERIK

840D / 840D sl / 810D Error Code Diagnostics

CNC machine control systems for machining centers, lathes, and multi-axis machines

Supported Control Units:

NCU 571.5NCU 572.5NCU 573.5CCU

Error Code Format:0-9, A-F (hexadecimal)

SINAMICS

S120 Fault Code & LED Diagnostics

Modular drive systems for servo and vector applications

Supported Control Units:

CU320-2 DPCU320-2 PNCU310-2 DPCU310-2 PN

Error Code Format:Fxxxxx (Fault) / Axxxxx (Alarm)

Input Controls

Pick the hex digit on your machine’s 7-segment display, then match the decimal dot.

Digit

0–9, A–F

Use the keypad or the small digit field. One hexadecimal character: 0–9 or A through F.

Dot Status

7-Segment Display

Start with the digit on your display

Reference: Siemens SINUMERIK Diagnostics Manual (6FC5297).

Note: 3 supported models (840D, 840D sl, 810D) share the same diagnostic manual (6FC5297) and use compatible error codes.

Common Replacement Units

Replacement part numbers (MLFB) for common NCU and CCU modules. Use these part numbers when ordering replacement units for your SINUMERIK system.