You have no speedo....sort it out!
Do you actually read anything before you comment
Okay, i'll give you that one, heavy duty week and a long night to let off steam, my bad
If the tabs on your sensor have broken off then your tacho is highly unlikely to be working fine, hence the error code?
That's like saying you've lost both your arms but it's made no difference to your swimming.
I'll say it again, 0rpm then 4000rpm is a speedo sensor error code, and in the same breath you're telling us that your speedo sensor has broken lugs.
I'm not quite sure what more you'd like me to suggest, because you've told us the problem
and the cause?
Also, the tacho did not drop, your rev counter needle did.
If your tacho dropped then you were riding backwards.