Gyro sensor and accelerator sensor not working after water damage?

@demonking you are not saying how you managed your water damage. That is something you will have to start with.

For now you want to stop continuing to try to charge, sync or otherwise use your phone. This potentially can make a bad situation worse as this may further damage your phone.

The next thing to do is to clean it. Disassemble your phone using these guides Xiaomi Redmi Note 9 Pro or if you prefer this video. Remove your motherboard as well as your charging board. Start with the motherboard since I am going to suggest that you completely replace the charging board (sub-board). That way, the sub_board can be ruled out as the cause for the data transfer issue etc. For now, focus on the main board.

You must remove all the EMI shields from the board.. If you do not remove those, you might as well not do anything. After you removed those, clean the whole board, connectors and all with +90% isopropyl alcohol. Follow this guide. Even so it was written for a iPhone 3G all the points are still pertinent to your phone as well. While you clean your board, check for any obvious damage, like burned or missing components etc. Do check all flex cable ends and all connectors as well. I can not stress the importance of a good cleaning enough, so do it over and over while replacing the alcohol after each cleaning.

Once it is properly cleaned, you do want to go ahead and replace the battery and the charging board (sub_board) All these steps are to avoid delayed failure caused by corrosion. Best thing to do would be to clean it with an ultrasonic cleaner, but if you do not have access to one, this will at least help. Once all this is done, reassemble your phone and reevaluate. Until it is cleaned, everything will only be a guess.

Now, you do want to go ahead and check the sensors that you feel are not working. Just because the Gyro or the Accelerometer does not work, does not mean you have to replace those IC's. It means that you will have to check the circuitry and components for those sensors. Even a bad components in those circuits can be the cause for its failure. Don't just go and replace components for the sake of replacing them. Since you are now getting in the board level of the repair, you have to make sure that you have the right tools and skills to perform board level repairs. If you do not, then I would suggest that you do a good online search for somebody that has specialized in water damage repair.

Just in case you have the tools and skills to perform this repair, you will have to have the schematic and component layout for your phone. It is with that schematic that you will need to check the sensor circuitry. Xiaomi Redmi Note 9 Pro SchematicXiaomi Redmi Note 9 Pro Component Layout

Even with all this, water damage has only a small chance to be fully repaired, but at least you can give it a try