DTC P0338: CKP Sensor Circuit High Duty Cycle: Description

WARNING: This page is about a different car, the 2002 Saturn Vue. However, it is still accessible from the selected car via links, so may be relevant.

The Crankshaft Position (CKP) sensor produces an AC voltage of different amplitude and frequency depending on the velocity of the crankshaft. The CKP sensor works in conjunction with a 58 tooth reluctor wheel on the crankshaft. Each tooth is spaced six degrees apart with one span having a 12 degree space that is uncut. This uncut portion creates a pattern that enables the ECM to determine top dead center for cylinder No. 1 and its mating cylinder, cylinder No. 4. The Camshaft Position (CMP) sensor is then used to determine when cylinder No. 1 is on its compression stroke. With both CKP sensor and CMP sensor inputs, the ECM can properly synchronize ignition timing, fuel delivery and spark knock control. The ECM uses a pull-up voltage of 2.5 volts on each CKP sensor wire used for the reduction of noise interference from electromagnetic generating devices. DTC P0338 will set if the ECM detects more CKP sensor signal pulses within a certain number of crankshaft revolutions when the engine is cranking or running. This indicates that the CKP sensor circuit is experiencing electromagnetic interference, the sensor frequency characteristics have changed or a short to voltage in the wiring may exist.