E90 Error,How do I fix or clear the E90 error I am getting on my spa?

The E90 code on the Intex spa is due to a dirty water flow sensor. ... The black wire is plugged into a white wire, carefully unplug it and unscrew the sensor. Clean it good and blow out the hole it goes in. This will fix the code and you will be back in business https://www.justanswer.com/pool-and-spa/ap9qh-i-m-having-error-code-90-intex-hot-tub-intex.html

https://intexwetset.co.uk/faqs/what-does-code-e90-mean-what-should-i-do-if-code-e90-appears-on-my-air-bubble-spa-control-panel/

Videos as well. It is a common error

https://www.google.com/search?safe=off&rlz=1C1QJDB_enCA643CA644&sxsrf=ALeKk018uuznYQiZxVpxtAwmq3uARs0WZw%3A1609886164527&ei=1On0X-rbH5uh5NoP-Z2OyA0&q=intex+pure+spa+bubble+jacuzzi+e90

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I to have run into this issue and i saw a repair using a piece of brass rod. If you open the motor cap where the impeller is located you will find the impeller guide shaft is made of a cheep piece of plastic and has broken it is a magnetic motor guided assembly and all it does is hold the impeller in the exact place. well i have found just the piece that you can fashion a quick fix from and you can find it at any hardware store. I happened to get mine from home Depot. buy a toilet handle brass lift kit paid 3.00 for it.
the larger piece is a perfect fit cut it to size and file the end of any sharp edges. works great

If alarm code E90 is displayed on the control panel, it means no water is flowing through the system. Check with Intex for a repair manual ( On line and google..)

Call Intex and follow up with their warranty precedures to fix/replace. Dont do anything that would void the warranty, atleast until they say they wont fix/replace it.

You have an owners manual I hope, with
the codes & trouble charts

I would say call the pool & spa store & have
someone trouble shoot the problem

The E90 error code is not a specific code. The error code E90 is just a group error code. It is indicating a communication error between the two boards in your machine. It does not indicate where the problem may be. A power glitch may have caused the E90 error code or a loose connection. One of the control boards could have failed. If it did not clear by unplugging the washer, I recommend a technician come out to properly diagnose your washer.