> For the complete documentation index, see [llms.txt](https://knowledge.illumina.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://knowledge.illumina.com/instrumentation/miseq-ruo/instrumentation-miseq-ruo-troubleshooting-list/000001458.md).
# Troubleshooting Reagent Valve errors on the MiSeq
**Background:**
Users may encounter a "Reagent Valve" error during runs or washes:
* This error can include the phrase “ReagentValve ReadResponse”, or state “The reagent valve will not respond”.
In either case, the error refers to the valve that selects which reagent is pumped across the flow cell. If the error occurs mid-run, the run will stop and cannot be resumed. This error is usually caused by either software communication failures or in rarer cases by a faulty reagent valve.
**Troubleshooting steps:**
1. **Power cycle** the MiSeq following the guidance in the Illumina Knowledge article [How to Power Cycle the MiSeq](/instrumentation/miseq-ruo/instrumentation-miseq-ruo-reference_material-list/000001894.md).
2. If there are no issues with MiSeq Control Software (MCS) re-initialization, perform a **wash** which will test normal operation of the reagent selector valve.
1. **NOTE**: If a run fails with the valve error, a manual post-run wash will be required before setting up the next run
3. If there are no issues during MCS initialization or the wash, proceed with setting up your next run.
4. If MCS fails to initialize or the wash does not complete successfully with a similiar reagent valve error, contact [Illumina Technical Support.](https://www.illumina.com/company/contact-us.html#/)
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| *For any feedback or questions regarding this article (Illumina Knowledge Article #1458), contact Illumina Technical Support* [*techsupport@illumina.com*](mailto:techsupport@illumina.com?subject=Question%2FFeedback%20Regarding%20Illumina%20Knowledge%20Article%20#000001458%20-%20Instrumentation%20\&body=Dear%20Illumina%20Technical%20Support,%0D%0A%0D%0A)*.* |
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