NB Miata Speedo issue

The past couple of days my speedometer intermittently fails. I'll be driving along and all of a sudden the needle just drops to zero. After a few seconds to a minute it recovers and comes back to life. The other instruments all remain steady and fully functional. Haven't been able to figure out if there is something in particular that causes it (I've only seen it 4 times or so).

The car is a 2005 Mazdaspeed with a 6 speed manual. It is normally a car that I do routine fluids changes on and save my projects for one of my other cars so I do not have a service manual for it. I'm guessing speed sensor or a loose connector somewhere in the wiring harness. Any ideas of where to start?

The signal comes from a sensor on the transmission. That's the easiest place to start.

yes.. maybe you hit something that pulled the wires loose? Some dirt on the contacts? Could also be a bad sensor

The speedo sensor crapped out on my 2004 MazdaSpeed at 22k miles. The symptoms were the same. Check for a loose connector first, but the sensor is known to fail. The shop manual says to drain the tranny oil before pulling the sensor, but I put the rear on jack stands and didn't lose any oil from where the sensor mounts. I believe the sensor is behind a brace/undershield making it harder to check but less likely to take a hit from debris.

Thanks guys. I'll get under there and take a look this weekend. I'm ok with draining the tranny and replacing the oil as I'm still running what came from the factory in there.

I'm pretty sure you don't have to drain the trans.

Thanks Keith.