Alarm guide · Panasonic · Updated October 2026
Panasonic Err 21.0 / 21.1 alarm: Encoder communication disconnect error protection / Encoder communication error protection
Panasonic MINAS Err 21.0 means the drive lost its connection to the encoder; Err 21.1 means the encoder data was corrupted. The usual causes are a loose connector, a damaged encoder cable, noise or poor earthing, or a faulty encoder.
By Suresh Sankaran, founder of Star Automations, servo motor repair since 1998.
What the alarm means
Panasonic MINAS Err 21.0 means the drive lost its connection to the encoder; Err 21.1 means the encoder data was corrupted. The usual causes are a loose connector, a damaged encoder cable, noise or poor earthing, or a faulty encoder.
Safe first checks
General guidance only. Follow the drive manual and your site's electrical safety rules. Power off, and let the DC bus discharge, before touching connectors.
- Power off and reseat the encoder connector at both ends.
- Inspect the encoder cable for damage and check its length and type.
- Check the earthing of the motor and drive.
- Route the encoder cable away from power cables.
- Try a known-good cable.
When to send it for repair
Send the motor when the alarm stays with a good cable or follows the motor. The encoder is tested, repaired or replaced, and aligned before the run test.
See Panasonic servo motor repair, encoder repair and servo drive repair.
Questions
Can I clear the Err 21.0 / 21.1 alarm and keep running?
A reset may clear it for a while, but a feedback alarm usually comes back until the cable, connector or encoder is fixed. Running with an intermittent feedback fault can stop the axis without warning, so find the cause first.
Is it the motor, the cable or the drive?
Swap with a known-good cable first, then swap the motor to another axis if you can. If the alarm follows the motor, send the motor. If it stays on the axis with a good motor and cable, send the drive. We test both when you are not sure.
How long does repair take?
Emergency repair is done the same day where the fault and parts allow, urgent in 3 working days and standard in 7 working days, counted from when the unit reaches our bench and the quote is approved. Every unit returns with a printed test report.
Can I get an exchange unit?
If we hold a matching unit, Servo Swap ships a tested exchange unit while yours is repaired. Mark "line down" on the request form and add the part number.
Brand names identify the units we repair. Star Automations is an independent multi-brand repair company and is not an OEM service centre.