Hyundai Repair: Santa Fe (check engine light, vehicle speed sensor, smae time

Question
The check engine light came on this morning
(71,696 miles) - the speedometer and odometer have quick operating.  The TACh is still functioning.
Car seems to be running as smoothly as before.

Any ideas as to why these happen at the smae time.
No other problerms with the automobile - only service items have been the oil changes.

Answer
Presuming you have a four cylinder, I'd suspect the issue to be the vehicle speed sensor (on top of the differential of the transmission).  When the Engine Control Module doesn't see the vehicle speed sensor signal, it'll set trouble code P0500 and turn on the check engine lamp.  So, that'd be a single fault causing all those things to happen.  The sensor has a plastic gear on it which tends to strip also.  I'd recommend replacing the sensor and gear at the same time.

If you've got a V6, then the check engine lamp is likely unrelated to the vehicle speed sensor.  On the V6, the vehicle speed sensor operates the speedometer/odometer only, and the computerized components don't see this reading; they use instead the right front wheel speed sensor.