Hyundai Repair: Vehicle Speed Sensor, vehicle speed sensor, tone wheel

Question
I recently replaced the left and right half shafts on my 2001 Elantra (manual transmission). When I pulled out the driver's side half shaft, I lost some gear oil, so naturally I had to refill it.  I tried to get what I thought was the normal transmission fill plug out, but it would not budge.  So, I removed the VSS and used that hole to replace the gear oil.  Later that day, my check engine light came on and I had the code checked (P0501 I believe), which indicated the VSS wasn't being read by the PCM.  The speedometer works fine and the wiring all seems fine.  I replaced the VSS, but still get the same code.  Any ideas what the problem could be?

Answer
The sensor your engine control module (ECM) uses to determine vehicle speed is the right front wheel speed sensor.  If you damaged the sensor replacing the axle or the new axle doesn't have the tone wheel on it, that would be the source of your problem.