The ignition/distributor engine speed input circuit is monitored by the PCM while the engine is cranking and running. The PCM detects the engine speed by using the distributor mounted magnetic pickup assembly and the distributor rotor. The magnetic pickup assembly generates an AC voltage that is proportional to the engine speed and the PCM supplies the AC voltage reference signal to the magnetic pickup assembly. The rotor in the distributor modulates the AC voltage signal generated between the magnetic pickup assembly and ground. The PCM can then compute the engine speed based upon the modulated signal.
If the PCM detects a circuit malfunction due to an open or shorted circuit, it will set code P0320 and illuminate the MIL.
