The Distributorless Ignition System (DIS) is used on the 2.8L VR6 (AAA) engine exclusively. The DIS system eliminates any moving parts, providing a completely wear-free, solid state ignition system.
The Distributorless Ignition System does not use a conventional distributor. The heart of the system consists of a three separate ignition coils, which actually fire two cylinders simultaneously. These coils are controlled by the ECM, based on the inputs of the various sensors on the engine.
The Distributorless system uses a "waste spark" method of spark distribution. Companion cylinders are paired and the spark occurs simultaneously in the cylinder with the piston coming up on the compression stroke and in the companion cylinder with the piston coming up on the exhaust stroke.
The DIS system is composed of the following components:
Electronic Control Module (ECM)
-The ECM is the "brain" of the ignition system. The ECM controls when the spark occurs, based on the input from the various sensors on the engine, including the knock sensor, coolant temperature sensor, crankshaft position sensor, and the oxygen (02) sensor.
Ignition Coil Pack
-The ignition coil pack actually consists of three separate double-sided ignition coils. These coils operate in the same manner as a conventional coil.
-A knock sensor is a peizo-electric device that senses detonation or pre-ignition from the engine block. When the engine begins to knock, the sensor produces a small amount of voltage. This voltage is detected by the ECM, which typically retards the ignition timing slightly to prevent detonation. AAA engines use two sensors to detect detonation.
Crankshaft Position Sensor
-The crankshaft position sensor determines the exact position of each piston in the engine. The information from this sensor allows the ECM to precisely control when the ignition occurs. Typically, the crankshaft position sensor is located on the engine block. On some engines, this sensor is located inside of the distributor itself.
Camshaft Position Sensor
-The crankshaft position sensor performs the same function as the crankshaft position sensor; providing the ECM with information on the position of the engine. This sensor, located on the "intake" side of the engine block, near the flywheel, provides the ECM with the information necessary to precisely control when ignition occurs.