Code 842: SUB PROGRAM NESTING EXCEEDED
Issue Description & Safety Warning
The Mazak Mazatrol Matrix CNC has triggered a critical SUB PROGRAM NESTING EXCEEDED 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
Type of error: B — Registered data (the program or tool data includes an error) Stopped status: I — Reset stop Clearing procedure: O — Eliminate cause -> press reset key Display colour: Red On-screen parameters (shown in parentheses): WNo., NNo., BNo. Cause: 1. The total number of sequential calls of subprogram has exceeded eight. 2. Executing a program that includes an “M99” command has been attempted in the direct operation mode of HD, IC memory card or the Ethernet. 3. Invoking a program stored within the HD, IC memory card or the host has been attempted from the HD, IC memory card or the host. Action: 1. Check the number of subprogram calls, and correct the program so that the number of calls does not exceed eight. 2. Do not include an “M99” command in the main program to be executed in the direct operation mode. 3. Do not invoke any subprograms of the HD, IC memory card or host from the main program of the HD, IC memory card or the host.
Source: Mazak Mazatrol Matrix — Parameter List, M-Codes, Alarm Manual (Section 3 Alarm)
Last reviewed: 2026-07-01 · Verified against the manufacturer’s official documentation.
About Mazak Mazatrol Matrix CNC Alarms
Mazak controllers include extensive self-diagnostics that flag or halt the machine when a fault is detected. Error code 842 on the Mazatrol Matrix CNC identifies one specific fault condition — its documented cause and the official corrective steps are listed above, sourced from Mazak's service documentation. Always confirm against the manual for your exact machine configuration and follow LOTO procedures before servicing.
Complete Alarm List: 714 Mazak Mazatrol Matrix CNC codes.
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