Distributor Operation

The distributor assembly directs the spark from the ignition coil assembly to the proper spark plug secondary wire through a rotor. Spark plug secondary wire connectors in the cap are arranged for convenience in routing spark plug wire harness assemblies. The corresponding cylinder number is molded into the distributor cap next to each spark plug secondary wire connector.

The distributor assembly also contains a signal disk and two optical camshaft position (CMP) sensors assemblies that provide signals to the Powertrain Control Module (PCM) for timing control. One sensor sends 360 pulses per crankshaft revolution for high-resolution timing control. The other senses eight disk slots of variable length, providing four pulses per crankshaft revolution for a low-resolution signal that tells the PCM which spark plug is being fired. The PCM can determine if one of the timing inputs is not being received by comparing the two inputs. If the PCM detects one timing pulse without detecting the other timing pulse, diagnostic trouble locks 16 or 36 will set. Power for the optical CMP sensor assemblies, a system ground, and the two CMP sensor assembly signals is transferred between the PCM and the distributor assembly through a shielded harness connected to the four-terminal connector on the distributor.

The reference signals toggle between 0 and 5 volts as the camshaft assembly turns. Therefore, an open circuit, a short to voltage, a short to ground, or a defective sensor inside the distributor assembly can prevent the voltage from pulsing at the PCM.