Mitsubishi Electric MELSERVO-J5 (MR-J5) alarm AL.016: Encoder initial communication error 1
Alarm AL.016 on a Mitsubishi MR-J5 servo amplifier is Encoder initial communication error 1: there is a communication error between the encoder and the servo amplifier during initial communication. It is the MR-J5 equivalent of MR-J4 AL.16.
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When it happens
- At power-up, as the amplifier establishes encoder communication
- After a software reset on servo motors with functional safety (Mitsubishi says to cycle power if AL.016 occurs)
- After motor, cable or amplifier replacement
Reading the subset
| Subset | What it tells you |
|---|---|
| 016.1 / 016.2 | Receive data error 1 / 2. |
| 016.3 | Receive data error 3: unused axis not disabled, cable disconnected, communication method setting, control power. |
| 016.5–016.7 | Transmission data error 1–3: same checks as 016.1. |
| 016.A–016.F | Process error 1–6: amplifier, encoder or surroundings. |
Likely causes and checks
1Encoder cable disconnected, wired wrongly or shorted
- Points to it
- Alarm at every power-up.
- Check
- Check the encoder cable for disconnection, incorrect wiring or shorts; replace or repair it.
2Communication method servo parameter wrong (two-wire / four-wire)
- Points to it
- Detail 016.3 after commissioning.
- Check
- Set [Pr. PC04.3] ([G] [B]) or [Pr. PC22.3] ([A]) Encoder cable communication method selection to match the cable.
3Unused axis not disabled on a multi-axis amplifier
- Points to it
- Detail 016.3 on an axis with no motor.
- Check
- Disable the unused axis with the disabling control axis switches (SW3-2/SW3-3/SW3-4).
4Control circuit power supply unstable
- Points to it
- Detail 016.3 with control-power dips.
- Check
- Check the control circuit power voltage for instantaneous power failures.
5Amplifier or encoder failure, or noise
- Points to it
- Cable and settings check good.
- Check
- Replace the amplifier, then the servo motor, checking repeatability; check the power supply for noise and the connector for shorts.
Telling it apart
- AL.016 is initial communication (start-up); AL.020 is encoder normal communication error 1 during operation.
- MR-J5 numbers are three digits: AL.016 on MR-J5 is the same alarm as AL.16 on MR-J4.
Relevant parameters
| Parameter | Name | Why it matters |
|---|---|---|
| PC04.3 ([G] [B]) / PC22.3 ([A]) | Encoder cable communication method selection | Must match the cable (two-wire or four-wire). |
Evidence to collect
- Full alarm and detail number
- Amplifier model and firmware
- Encoder cable part number and length
- [Pr. PC04.3] or [Pr. PC22.3] setting
- Swap test results
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