Crankshaft Position Sensor: Description and Operation

DESCRIPTION
The PCM receives signals from the crankshaft position sensor to determine the position of the engine at various degrees of rotation.

The EI module does not receive a signal from the crankshaft position (CKP) sensor. Instead the CPK sensor signal is being received and processed by the PCM. The EI module does, however, contain circuitry to determine camshaft position without using a camshaft sensor, by use of compression sense ignition (CSI). The CSI circuitry makes use of the characteristics of a waste spark ignition system, while monitoring a sequence of spark plug gap breakdown events. Capacitive pickup plates located under the 1/4 coil are used to determine whether #1 or #4 fired on a compression stroke. This capacitive sensing device is similar to inductive pickups used on engine analyzers and oscilloscopes.

OPERATION
Crankshaft rotation initiates CKP pulses. With sensor connected to PCM, any valid CKP pulses will initiate reference pulses.

Crankshaft Position Sensor-Positive
The crankshaft position (CKP) sensor positive line is tied to the positive connection of the polarized variable reluctance crankshaft position sensor. The peak positive voltage depends on engine rpm, and ranges from 300 millivolts to 125 volts.

The CKP signal defines engine position. A CKP pulse occurs at each TDC, at 60 degrees after top dead center (ATDC), and at 120 degrees ATDC. A seventh pulse referred to as the sync pulse, occurs at 70 degrees ATDC of cylinder #1.

Crankshaft Position Sensor-Negative
The CKP negative line is tied to the negative connection of the polarized variable reluctance crankshaft position sensor. The peak negative voltage depends on engine rpm and ranges from -250 millivolts to -120 volts.


Engine Stall
If engine stalls, CKP pulses stop due to lack of engine rotation. Within 500 milliseconds after the last CKP pulse, any charged coils are fired. No more firing events will occur until engine rotation resumes. If an engine stall occurs where reference pulses are not received after the engine was running and the ignition volts indicate the ignition was not turned Off, an DTC P1599 will set.