Likely you need instrument pack.
You can check signal to verify. With key off hold trip button in, keep holding and start car. Keep holding trip button until airbag light goes out then release. It should say test mode on pack.
Keep pressing and releasing trip button until it shows tacho in on display. Compare to what needle shows.
If when you start car, the needle returns to zero, you can do same thing without starting car, just turn to position 2 instead of starting. If reading shows one thing and needle is off, you need pack.

 

FJT, that's really a cool feature to be able to use the 'test' mode to check on some things, only ever heard about that from this forum. How can we find out what all of the modes are using this? is it documented somewhere, or only technician knowledge only?

Which model years for the x, s, xk and xj does this work on? Sorry, just curious.

 

They do not provide the info to us either really. Justiind of figure it out as we go.
All Xs, 04+ Xj, 03+ Stype, I think 03+ XK. Maybe you can check that and let us know. If not 03 XK, definitly 07.
Lots if info in that screen. Test lights, gauges, pull codes, fuel levels, speedometer checking, tach, lots of others that we have still to figure out LOL

 

You need to leave it on tacho in. Drive around and when gauge acts up look at what tacho in says in screen.

 

Unfortunately that is a mechanical problem with yourinstrument pack. Good news is, you saved yourself mega bucks in diag fees. You can just go to dealer and order the pack. Once it arrives you need both keys as the IPK needs to be programmed.
Where are you located?

 

Ahhh sorry....too far away for me.
As annoying as the tach issue is, you may learn to live with it when you find out the price of the pack. Alternative may be to get one from a junkyard? I am pretty sure it can be programmed to your car as a new module, but cannot confirm that.