Enhanced Ignition System Operation

Distributor:

SYSTEM OPERATION
The Enhanced Ignition system used on the On-Board Diagnostics (OBD) II engine somewhat resembles the current Distributor Ignition (DI) system. However, the system has been greatly enhanced to make it compatible with the new OBD II regulations. The Enhanced Ignition system provides spark at precisely the correct time to ignite the air/fuel mixture for optimum performance and fuel economy. The system consists of the following components:

^ Vehicle Control Module (VCM).
^ Distributor.
^ Ignition Coil Driver Module.
^ Ignition Coil.
^ Crankshaft Position Sensor.

The ignition module used on Distributor Ignition (DI) systems in the past is not used on this system. The Ignition Control (IC) and Bypass functions are now controlled by the VCM controller.

The crankshaft sensor, located in the front engine cover, is perpendicular to a target wheel attached to the crankshaft. The target wheel is equipped with slots situated 60° apart. As the crankshaft rotates, the target wheel rotates past the crankshaft position sensor. The "rising" and "falling" edges created by the slots cause a signal to be sent back to the VCM. This signal occurs three times per crankshaft revolution and is referred to the "4x" signal.

The VCM then utilizes this 4x signal to provide the correct spark to the engine by way of the single coil driver module. The single coil driver module is basically an electronic switch that when commanded by the VCM, will cause the primary coil voltage to breakdown, energizing the secondary coil and providing spark via the coil wire to the distributor cap. The Enhanced Ignition System distributor consists of the following components:

^ Cap and Rotor.
^ Camshaft Position Sensor.
^ Gear drive and shaft.

The distributor shaft is driven by the camshaft and rotates providing spark to the correct cylinder by way of the cap and rotor. The camshaft position sensor functions much like the crankshaft sensor previously described but provides only a "1x" signal to the VCM. That is, for every 2 rotations of the crankshaft, there is 1 rotation of the camshaft. It should be noted that the camshaft position sensor will not affect driveability. The sole purpose of the camshaft position sensor is to provide the VCM with the necessary information for the misfire Diagnostic Trouble Code (DTC)s.

IGNITION CONTROL (IC)
All IC and Bypass functions are controlled by the VCM software. This reduces the number of circuits outside the controller and ultimately reduces the possibility for shorts or opens in those circuits that could result in driveability complaints or diagnostic trouble codes.