The Fanuc “wrong data is used” type of error appears when you try to load data the control cannot accept — during an SRAM restore from the boot monitor, a parameter or program input over RS-232 / memory card, or after swapping a board and reloading a backup. The control is telling you: this data does not match this machine. Here are the real causes, in the order we see them in the workshop, and the fix for each.
Cause 1 — The backup is from a different machine or control version
The most common case. An SRAM backup (SRAM_BAK / ATA backup) is tied to the exact control model, software series/edition and option configuration it came from. Restoring a file from a “sister” machine, or from the same machine before a software/option change, is rejected — or worse, partially accepted.
- Check the software series and edition on the SYSTEM screen (e.g. D4F1-24.0) against the machine the backup came from — they must match.
- An SRAM image from a different memory size (e.g. 1MB vs 3MB board) will not restore. Use the backup made from this control, or restore data area by area (parameters, programs, offsets as text files) instead of the full SRAM image.
Cause 2 — Restoring the wrong data type to the wrong screen
Text-format data must be loaded on its matching screen: parameters on the parameter screen, offsets on the offset screen, pitch error on its own screen. Sending a parameter file while the program screen is waiting (or vice versa) produces format/illegal-data errors.
- Open the captured file on the PC: parameter files start with N-numbers matching parameter numbers; programs start with O-numbers. Load each on its own screen.
- On 2-path lathes, load each path's data with that path selected.
Cause 3 — Corrupted or truncated file
- A capture that was cut short (handshake mismatch, cable noise) fails on input — often part-way through, leaving the control with mixed old/new data. Verify the file ends with % and has sensible size before loading.
- Memory cards: use a small (≤2GB) card formatted FAT16 — large FAT32 cards are a classic source of read errors on 0i-B/C era hardware.
- If a partial load has already happened, do not power off in panic — reload the complete correct file immediately, then power cycle and verify.
Cause 4 — Protection and mode blocks misread as data errors
- PWE not enabled → parameter input rejected. See our write-protection guide.
- Program range O8000/O9000 locked by parameter 3202 (NE8/NE9) → those programs in the file are skipped or the load aborts.
- Wrong mode: most inputs need EDIT mode (programs) or MDI (parameters).
Cause 5 — Option parameter mismatch after board replacement
After a memory/main board swap, the control may boot with default option data. Loading your parameter backup then throws data errors on parameters for options the control no longer ‘thinks’ it has (e.g. rigid tapping, additional axes, macro executor).
- The option information must be restored first (it lives in the SRAM image / the builder's option file). If options were lost with the board, the machine builder or Fanuc must reissue them — parameter files alone cannot recreate them.
- This is why we always advise keeping the full SRAM backup AND area-by-area text backups — each saves you in a different failure. See the complete backup guide.
Quick diagnosis table
- Error immediately at start of load → wrong data type / wrong screen / protection active.
- Error part-way through → truncated or corrupted file, or a locked program range mid-file.
- SRAM restore refused entirely → backup from different control / memory size / software version.
- Load succeeds but alarms afterwards → option mismatch or the wrong machine's parameters — stop and verify before moving axes; wrong axis parameters can crash the machine at first jog.
Related guides
- Fanuc parameter backup — 0i/16i/18i/30i
- Fanuc 10/11/12 backup & restore via RS-232
- Removing Fanuc write protection