Fanuc Servo Alarm Reference Chart: CNC SV Code, Amplifier 7-Segment Code and Diagnostic Number

🚨 Scope and compliance: number ranges, code families and diagnostic-number practice are summarised from the public chapters of the FANUC servo amplifier maintenance manual, CNC maintenance manual and parameter manual shipped with the machine. Three existing pages on this site cover the three systems separately: Fanuc servo amplifier 7-segment codes, the Fanuc servo load meter and the SINUMERIK alarm list for comparison. Manual text and code tables are copyright protected: this page explains the relationship between the three systems, how to cross-check against your own manuals and the troubleshooting order. It reproduces no code-table screenshots and offers no manual download link, file mirror or archive. Alarm text, diagnostic numbers and display characters vary with the control series (0i / 30i / 31i), amplifier generation (alpha SVU / alpha i SVM / beta i) and software version, so always use the manuals shipped with your machine.

30-Second Triage: Which Code System Are You Looking At

Table 0　Six field clues and their first stop

Three Code Systems: Why One Fault Shows Two Codes

The three systems are produced by three different devices, so they cannot be merged and there is no one-to-one correspondence:

1. CNC-side SV alarm: a system-level alarm raised by the CNC from the axis control card, FSSB and interface signals, written as SV plus a number (for example SV0401). It describes what the CNC believes is wrong.
2. Amplifier seven-segment code: a self-diagnosis character shown on the servo or spindle amplifier’s own display, describing what that module itself detected.
3. Diagnostic number (DGN): status bits and values on the CNC diagnosis screen, used to cross-check the evidence behind the first two, such as ready signals, position error and load current.

Seeing two codes for one fault usually means the CNC-side alarm is a secondary result. For example, if the amplifier does not assert servo ready for some reason, the CNC reports SV0401 while the amplifier shows its own code. The official order is to treat the first alarm that occurred first: read the amplifier-side code, then interpret the CNC SV number.

Table 1　Origin and portability of the three code systems

CNC SV Numbers: Ranges and Official Sample Rows

SV alarms come in functional families; the on-site searchable list is in our servo alarm code table SV0301-SV0441. The rows below are samples whose official wording is consistent across independent sources and does not depend on the amplifier generation, included to demonstrate how to read one row:

Table 2　Six verifiable SV number samples (not a per-number full table)

🚨 A conflict worth calling out: some online tables describe SV0401 as “amplifier overheat” or “servo amplifier overload”, while the FANUC wording is servo ready signal (VRDY) off, a “not ready” condition rather than an overheat. When even one number’s meaning is wrong, a “one SV number plus one display character per row” universal three-way table has no credible source. This page does not provide one and does not recommend copying one. The “full three-way table” suggested in the brief is deliberately reduced here to a relationship framework, official samples and a cross-check method.

Amplifier Seven-Segment Codes: Single, Two-Digit and Dotted

Identify the module first; this is where most mistakes start:

Table 3　Three display families and their boundaries

One more common misreading: an IPM alarm only means the intelligent power module detected an abnormality; its detection covers overcurrent, overtemperature and a drop in its own control supply. It does not mean the IPM has definitely failed. Ordering a replacement drive board the moment you see 8. is one of the most expensive mistakes on site. See our A06B seven-segment code guide for the per-character detail.

Diagnostic Numbers: Why No Universal Cross-Reference Exists

The diagnostic number is the column that should never be hard-coded. One verifiable example: field material for SV0401 points to DGN 358 (convert to binary to locate the fault, common in robot and specific-series documents), while other material points to 200–204 (servo load and position-error class, see our servo load meter guide). Neither is wrong; the control series and configuration differ.

Table 4　Four constraints on the diagnostic-number cross-reference column

Action Column: What to Check, What to Replace

The value of a three-way table ends in “what next”. Ordering actions by cost avoids swapping boards first:

Table 5　Six action stages and the replacement threshold

Take a recoverable backup before changing parameters, and read the CNC-side parameter write protection basics before assuming an amplifier fault when a parameter simply will not write.

Official Manual Lookup and Version Checks

Table 6　Five official search keys and where to read them

Manual text and complete code tables are copyright protected; this page reproduces none and offers no download link, file mirror or archive. For number-by-number lookup, use the manuals shipped with your machine. Our PLC basic program guide FB1 / FB2 / OB100 covers a different layer (PLC project structure) and should not be confused with amplifier self-diagnosis.

Three Core Articles and Related Pages

Table 7　Further reading for each face of the three code systems

Frequently Asked Questions

How do I map a FANUC SV alarm code to the amplifier 7-segment display?

There is no official general mapping, and you should not try to build one. The SV number is a system-level alarm the CNC derives from interface signals, while the display character is the amplifier’s own self-diagnosis. They come from different devices and vary with control series and amplifier generation. Record the full CNC alarm text and the actual panel character (including any dot) separately, look each up in the matching manual for your machine, cross-check with diagnostic numbers, and treat the first alarm that occurred as the root cause.

What does a dotted 7-segment code like 8. mean on a Fanuc servo amplifier?

A dotted code is a distinct code type, not “an 8 with a decimal point”. On alpha / alpha i SVM units, 8 / 9 / A relate to L / M / N axis overcurrent while 8. / 9. / A. relate to the matching axis IPM alarm. But an IPM alarm only means the intelligent power module detected an abnormality (overcurrent, overtemperature or a drop in its own control supply): it does not prove the IPM has failed. Rule out external causes per your amplifier maintenance manual before deciding to replace it. Spindle amplifiers use a two-digit code system, so this rule does not apply there.

Which diagnostic number shows why SV0401 appeared?

It depends on the control series and configuration; there is no single answer. Field material points to DGN 358 converted to binary in some series and robot documentation, while 200–204 style servo status and load diagnostics are used for 0i-series cross-checking. Use the diagnosis chapter of the manual shipped with your machine, convert the value to binary and read each bit against the official definition. Do not copy a table from another series.

Last updated: 2026-11-11