4 (Argument: --)
Max I/O Modules Exceeded
Wago · PFC200 PLC
What does 4 (Argument: --) mean?
The maximum permissible number of I/O modules connected to the controller has been exceeded. This prevents proper system initialization and operation due to hardware limitations on the I/O bus capacity.
Common Causes
- Too many I/O modules physically connected to the controller's internal data bus beyond the specified limit.
- Controller hardware limitation on the total number of I/O modules supported.
- Configuration error in the PLC program attempting to address more I/O modules than are physically allowed.
Repair Steps & Checklist
Click steps to track your progress.
- 1
Switch off the power supply to the controller.
- 2
Reduce the number of I/O modules connected to an acceptable value.
- 3
Switch the power supply back on to the controller.
Verified technical data. Last updated: March 2026
Related Faults
Source: Wago PFC200 PLC