Hyundai Repair: Unknown codes, computer communication network, powertrain system

Question
The check engine light on my 2001 Hyundai Sonata V6 has come on three times.  My mechanic checked it and got three different codes.  He was only able to find an explanation for the first one:  P0715.  The other two were U3118 and CD307.  What do these mean?  Thank you for your help.

Answer
P0715 is for a problem with the signal received from the input speed sensor.  In 100% of the instances I've seen this code, the problem has been the input speed sensor itself.

U3118 doesn't apply to your vehicle.  It refers to a computer communication network error, and your vehicle has no such network.  CD307 is not a valid code.  C0307 could be a code used for an ABS/TCS system, but I can find no evidence Hyundai uses this code, either.  My suspicion is that your mechanic's scan tool isn't communicating with the vehicle.  If he's checking the powertrain system, all codes received should be of the format Pxxxx, where the x's represent numerals.