> ## Documentation Index
> Fetch the complete documentation index at: https://docs.wuji.tech/llms.txt
> Use this file to discover all available pages before exploring further.

# Maintenance

> [!NOTE]
>
> This page covers stop behavior and recovery for 2.1 devices, plus the user-serviceable boundary. To diagnose by symptom, see [Troubleshooting](https://docs.wuji.tech/docs/en/wuji-hand/beta1/troubleshooting).

## Safe Stop and Fault Recovery

### Fault Severity and Stop Behavior

Each joint reports its current error code through `joint_diagnostics`. Decode it with `WujiHand2.describe_error(code)`, which returns an object carrying the error name, description, severity, and clear policy:

| Severity | Meaning |
| - | - |
| `Warning` | A non-critical condition, without a stop |
| `DeferredStop` | Deferred stop |
| `ImmediateStop` | Immediate stop |
| `Fatal` | Fatal error |

| Clear policy | Meaning |
| - | - |
| `AutoClear` | Clears itself once the condition goes away |
| `ManualClear` | Needs a `clear_fault` call |
| `NonClearable` | Can't be cleared, so power-cycle the device or contact technical support |

For an unknown error code, `describe_error` returns `None`. For the field definitions, see [SDK Reference](https://docs.wuji.tech/docs/en/wuji-hand/beta1/sdk-reference/diagnostics#joint_diagnostics-sub).

### Emergency Stop

In an emergency, stop the whole hand at any time. The call takes no mask:

```python theme={null}
hand.emergency_stop()
```

### Clear Faults and Reset Safely

1. Confirm nobody is touching the hand and the device is at rest.
2. Remove the external cause, such as a jam, an overload, or a pulled cable.
3. Call `hand.clear_fault()` to clear every joint, or pass a mask to clear specific joints.
4. Subscribe to `joint_diagnostics` again and confirm no error code is active.
5. Enable again and resume from slow, small motions.

Error codes with a `NonClearable` policy survive `clear_fault`, so power-cycle the device. If one persists, contact technical support.

### Status Light and Stop States

The back-of-hand status light runs from the device itself and shows the current state without a host connection. 2.1 uses priority numbering, so when several states coexist the light shows them in this order: fatal error, joint fault, firmware update, no joints detected, warning, running, power-up and self-check, and ready. For the full table, see [Back-of-Hand Status Light](https://docs.wuji.tech/docs/en/wuji-hand/beta1/overview.md#mechanical-structure) in Product Introduction.

## Maintenance and Consumables

### What You Can Service

| Part | User serviceable | Notes |
| - | - | - |
| Skin | Removable and replaceable | Always run the hand with the skin fitted |
| Soft pad | Replaceable | Power the device down before removing or refitting |
| Palm main board and driver board | Don't disassemble | Disassembly affects warranty, and the warranty terms aren't published yet |

> [!WARNING]
>
> Power the device down before removing or refitting the skin and soft pad. The flex cables on the finger surfaces are fragile, so avoid scraping and pinching them, described in [User Notice](https://docs.wuji.tech/docs/en/wuji-hand/beta1/user-notice.md).

### Daily Checks

Check before each day's use:

* No visible damage, with the skin fitted correctly
* No cable damage and no loose connectors
* Self-check passes, with the status light reaching white breathing

### Warranty and Support

Warranty coverage and the repair flow aren't published yet and will follow in a later update. If a prototype is damaged, contact your point of contact or [support@wuji.tech](mailto:support@wuji.tech) right away.


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