Question

2006 Acura RSX Automatic with P0718 code, how do you test to know what to replace?

Answer 1

P0718 Input shaft (Main shaft ) Speed Sensor intermittent failure

This code condition is more of an electrical condition than a mechanical condition, check for poor mating connection on the main shaft speed sensor. This sensor is a hall effect switch 

To test this, do a frequency test back probe the main shaft speed sensor White-Red connection and the Green-Yellow connection. at 30 MPH the frequency should be at 1.5hz and it should increase as the vehicle speed increases.