F122

I/O Board Failure

Allen-Bradley · PowerFlex 40 Adjustable Frequency

What does F122 mean?

This fault indicates an internal failure of the drive's I/O board. This is a critical internal hardware issue that typically requires replacement of the drive.

Common Causes

  • Internal component failure on the I/O board due to electrical overstress, manufacturing defect, or end of life.
  • Damage to I/O board circuitry from external overvoltage or overcurrent on connected I/O terminals (e.g., short to 24VDC, ground fault).
  • Contamination (e.g., metallic dust, moisture, corrosive gases) on the I/O board causing shorts or component degradation.
  • Poor connection between the I/O board and the main control board, leading to communication errors and diagnostics.

Repair Steps & Checklist

Click steps to track your progress.

  1. 1

    Isolate power to the drive. Visually inspect the I/O board for any signs of burning, arcing, swelling capacitors, or physical damage.

  2. 2

    Disconnect all external wiring from the drive's I/O terminals (digital inputs, analog inputs, relay outputs) to isolate external influences.

  3. 3

    Power on the drive with I/O disconnected. If the fault clears, methodically reconnect I/O devices one by one to identify the faulty external component or wiring.

  4. 4

    Using a multimeter, test the voltages at the drive's internal 24VDC I/O power supply terminals (if accessible and documented) to confirm it is stable.

  5. 5

    If the fault persists with all external I/O disconnected and visual inspection is clear, the I/O board itself has failed and the entire drive unit requires replacement.

Browse all codes in this manual (26)
Verified technical data. Last updated: March 2026

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Source: Allen-Bradley PowerFlex 40 Adjustable Frequency