# Troubleshooting Z Motor Positive soft limit too nonlinear at innermost test point on the MiSeq

The following Z stage/motor error indicates either a temporary communication loss between the stage and software or an issue with the stage hardware.

**Error**: “Z Motor: Positive soft limit too nonlinear even at innermost test point: Target = -20.000 um, actual = -16.287 um, error = 3.713 um, tolerance = 0.100 um (System.Exception)”

This error usually occurs at cycle 1 of a sequencing run, after a power cycle, or at the start of a wash.

**Troubleshooting Steps:**

1. Complete the post-run wash if not already completed.
2. Power cycle\\\* the instrument.
3. If the system initializes, run the Z stage Test in the System checks 5 times to verify the stage is moving correctly.

* MiSeq Control Software (MCS) v4.0: From Main Menu, select System Check.
* MCS v3.1 and older: From Welcome Screen, select Manage Instrument, select System Check.
* Follow the prompts on the screen to start the test, and repeat the test 4 more times (5 times total).

4. If all five Z stage tests pass, continue with the next run.
5. If the system does not initialize or if any of the Z stage tests fail, contact [Illumina Technical Support](https://www.illumina.com/company/contact-us.html#/united-states/technical-support) for further assistance.

\\\*For further information, search for Knowledge Base articles **How to Shut down or power cycle the MiSeq** and **How To Power Cycle the MiSeq Video.**

\
\
\ <br>

|                                                                                                                                                                                                                                                                                                                                                                        |
| :--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------: |
| *For any feedback or questions regarding this article (Illumina Knowledge Article #2241), contact Illumina Technical Support* [*techsupport@illumina.com*](mailto:techsupport@illumina.com?subject=Question%2FFeedback%20Regarding%20Illumina%20Knowledge%20Article%20#000002241%20-%20Instrumentation%20\&body=Dear%20Illumina%20Technical%20Support,%0D%0A%0D%0A)*.* |


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://knowledge.illumina.com/instrumentation/miseq/instrumentation-miseq-troubleshooting-list/000002241.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.