The speed sensor coupler is under the tank (you have to remove it) just by the inlet valve inspection cover.



The speed sensor 11D-83755-00 itself is held in place by a single bolt on the top of the gearbox, towards the rear on the left hand side. They are cheap and relatively easy to change.

If you can get access to a diagnostic tool, you can check the speedo sensor and whether a signal is received (or not) by the ECU.

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