What causes FANUC alarm 002?

Part program contains an illegal or malformed command related to the alarm condition. Missing required address word or parameter value in the program block. Programmed value is out of the allowable range. Conflict between active modal codes and the commanded function. Post-processor configuration mismatch for this Fanuc series.

How do I fix FANUC alarm 002?

1. Note the block number shown in the alarm screen and locate that block in the program. 2. Review the command in that block against the Fanuc programming manual. 3. Check for missing words, incorrect values, or conflicting G-code combinations. 4. Verify the program is post-processed for the correct Fanuc series. 5. Correct the program and dry-run at low speed before resuming machining.

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FANUC Controller

Program/G-code · Basic · 10-20 minutes

Alarm 002

Fanuc Alarm 002 - TV Check Error

Alarm 002 TV Check Error occurs when the CNC detects a parity or checksum error during program data input or transfer, indicating corrupted data. This typically happens during DNC operations, tape/memory card reads, or RS-232C serial communication when the transmitted data doesn't match the calculated check value. The 'TV' refers to the vertical parity check used in legacy tape verification systems.

FANUCProgram/G-codeBasic10-20 minutes

002

Fanuc Alarm 002 - TV Check Error

TV Parity Alarm

Root Cause Summary

Alarm 002 TV Check Error occurs when the CNC detects a parity or checksum error during program data input or transfer, indicating corrupted data. This typically happens during DNC operations, tape/memory card reads, or RS-232C serial communication when the transmitted data doesn't match the calculated check value. The 'TV' refers to the vertical parity check used in legacy tape verification systems.

Safety

Program may be incomplete

Causes and Fixes

1
Navigate to SYSTEM > PARAM and verify parameters 0020 (I/O channel), 0101-0104 (baud rate, stop bits, parity settings). Common setting is 0101=4 (4800 baud), 0102=2 (7-bit), 0103=2 (even parity), 0104=1 (2 stop bits).
2
Check parameter 0100 bit 0 (TV check enable). If set to 1, TV checking is active. Temporarily set to 0 to disable TV check and test if program loads successfully to isolate communication vs. data issues.
Disabling TV check removes data integrity verification. Re-enable after testing.
3
Inspect RS-232C cable and connector on JD1A/JD1B port. Test with known-good shielded cable. Verify pin continuity for pins 2 (RXD), 3 (TXD), and 7 (GND) at minimum.
4
Check parameter 0020 setting matches the physical I/O channel in use (0=reader, 2=RS-232C port 1, 3=RS-232C port 2). Mismatch causes data routing errors and TV check failures.

DIY Feasiblemedium confidence

Call a technician if:

·Main CPU board replacement needed
·Multiple servo amplifiers showing communication errors
·Parameter restoration fails repeatedly

Prevention

Regularly backup NC programs and parameters
Maintain clean servo cable connections
Monitor system diagnosis screens during preventive maintenance
Use UPS to prevent power-related data corruption

Common Mistakes

Permanently disabling TVC without finding root cause
Ignoring intermittent occurrences until they become persistent
Not checking cable connections before assuming hardware failure
Modifying TVC parameters without understanding their function

Related Alarms

001 003 004 090

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