The diagnostic code P0315 OBD2 refers to the relationship between the Crankshaft Position Sensor (CKP) and the Power Train Control Module (PCM). The vehicle's computer measures the changes between the reference points of the Crankshaft Position Sensor. Then, these measurements are compared to a reference that is stored in the PCM.
In case the variation or changes are above a calibrated percentage, this code is established. Generally, the fault is due to a problem in the electrical circuit, although mechanical problems may also influence.