# Troubleshooting MiSeqOverride.cfg Errors on the MiSeq

At the start of a run the MiSeq references the MiSeqOverride.cfg file to determine calibration location. This file provides information specific for the system. During preventative maintenance or service visits, Field Service Engineers (FSEs) may make minor updates to this file. If a syntax error is introduced, the MiSeq may fail to accurately parse the MiSeqOverride.cfg and stop the next run.

* "Config file 'C:/Miseq Config/MiSeqOverride.cfg, section '\[Focus Params]' defines 'CoarseFocusCenterZ=-0.0.169263'. which is an invalid float"

  ![](/files/zxey4J2lNafXsSmr39RO)

  ![](/files/zYgifV1fARm51P4oAy3x)

The specific section and element defined may vary, and this error will require consultation with an Illumina Technical Support representative to resolve. If this warning appears:

1. Locate the **MiSeqOverride.cfg** Configuration File on the instrument at based on the Windows Operating System (OS) version:
   1. Windows 7: **C:\MiSeq Config**
   2. Windows 10: **C:\ProgramData\Illumina\MiSeq**
2. Email Illumina Technical Support at <techsupport@illumina.com> with a picture of the error message and attach the **MiSeqOverride.cfg** file to your email.

A member of Illumina Technical Support will follow up to assist in troubleshooting.

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| *For any feedback or questions regarding this article (Illumina Knowledge Article #3299), contact Illumina Technical Support* [*techsupport@illumina.com*](mailto:techsupport@illumina.com?subject=Question%2FFeedback%20Regarding%20Illumina%20Knowledge%20Article%20#000003299%20-%20Instrumentation%20\&body=Dear%20Illumina%20Technical%20Support,%0D%0A%0D%0A)*.* |


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