STO Self-diagnosis Error

What does E99. mean?

This error indicates an internal fault within the inverter's STO (Safe Torque Off) input terminal or its internal safety circuit. This is a critical internal diagnostic failure, signaling that the inverter's safety function itself is not operating normally. It does not depend on the GS input operation selection, implying a fundamental issue with the safety hardware.

Additional Steps

Steps 1–2 are listed in Priority Fix.

1. 3

   Take measures to suppress any large noise sources in the vicinity of the inverter that could interfere with safety circuit diagnostics.

2. 4

   Verify that the GS1 and GS2 input terminals are correctly wired and that no external signals are inadvertently activating them.