b
Current Control Circuit Malfunction (ECM)
Fanuc · Alpha i Series AC Servo Motor and Spindle
What does b mean?
The circuit responsible for controlling the current within the ECM has malfunctioned. This is a critical internal fault affecting the ECM's ability to manage power flow.
Common Causes
- Internal ECM fault in the current control circuit.
- Wiring harness issue to the current sensor.
- Failure of the current control module itself (ECM).
Repair Steps & Checklist
Click steps to track your progress.
- 1
Inspect the control board of the ECM for visible damage or component failure.
- 2
Check power supply rails to the current control circuit.
- 3
Consult ECM diagnostics for specific sub-component failures.
Verified technical data. Last updated: March 2026
Related Faults
Source: Fanuc Alpha i Series AC Servo Motor and Spindle