Crankshaft Position Sensor: Description and Operation

The CKP sensor is located in the back of the engine block near the starter motor. It produces an AC voltage of different amplitude (as high as 125 volts) and frequency depending on the velocity of the crankshaft. The crankshaft has 7 machined notches, 6 of which are spaced 60° apart. The remaining notch is 10° before the #4 cylinder Top Dead Center (TDC) notch. The extra notch is used by the PCM to determine the position of the #4 cylinder and is necessary to synchronize engine position. The CKP sensor is used for fuel delivery, spark timing, misfire diagnostics and tachometer display.

TACHOMETER - The CKP sensor is used as an input to the PCM for tachometer information. The PCM uses voltage pulses from the CKP sensor to calculate RPM. The PCM sends an averaged tachometer message to the lip cluster over the Class II link every 100 ms. The PCM averages the tachometer information to ensure smooth tachometer fluctuations.

UPSHIFT TELLTALE - On manual transaxle vehicles, the PCM optimizes fuel economy by informing the driver when the transaxle should be shifted to the next higher gear. The PCM bases its determination on engine speed and engine load. When the PCM determines that the driver should shift to the next higher gear, it sends a message to the I/P cluster over the Class II link to turn On the Upshift telltale.