# 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.**

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