Adding faq speed sensor

docs/source/faq.rst

@@ -58,7 +58,6 @@ You're getting this error because you've probably reset your esieabot, thereby r
 
 If you use Windows, you can delete the file ``known_hosts`` which is located in ``C:\Users\<your user name>\.ssh\known_hosts``.
 
-
 Can't update esieabot
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@@ -67,4 +66,10 @@ If the ``apt update`` and/or ``apt upgrade`` commands fail, check that your esie
 I can't compile my C program: "pigpiod_if2.h: No such file or directory"
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-This error occurs because you are trying to compile a C program on a computer that does not have the pigpio library installed. It usually means that you are trying to compile your program on your computer and not on your esieabot.
+This error occurs because you are trying to compile a C program on a computer that does not have the pigpio library installed. It usually means that you are trying to compile your program on your computer and not on your esieabot.
\ No newline at end of file
+
+My speed sensor does not seem to work
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+
+- Check that your connections are correct by consulting the assembly guide of your esieabot. You will also find more information in the :doc:`documentation of the add-on board</understand/add-on-board/add-on-board>`.
+- If only one sensor is faulty, try connecting the left motor and left sensor to the right motor and right sensor connector and vice versa, without changing the wires. If the error has changed sides, it means the sensor is defective. If the error has remained on the same side, it is likely that the connector of a sensor wire is too loose. Try changing the wires connecting the sensor to the add-on board.