Direct Ignition System & Integrated Direct Ignition System

DIS is a distributorless system used on 1.9L, 2.2L, 2.5L, 3.4L and some 3.1L models. The 2.3L uses a similar system referred to as the Integrated Direct Ignition (IDI) system. The operation of both DIS and IDI is quite similar to operation of C3I system. Systems consist of 2 (4-cylinder) or 3 (V6) ignition coils, spark plug wires, ignition module (located under coil pack), a crankshaft position sensor, necessary wiring and the Electronic Spark Timing (EST) portion of the Electronic Control Module (ECM). On 2.3L, coils, module and spark plug connectors are all combined into one unit which plugs directly onto spark plugs.

Spark is timed by a signal sent from a crankshaft position sensor mounted through side of engine block instead of from a crankshaft position sensor mounted at crankshaft pulley (such as C3I). This signal is received by ECM (through ignition module) and is used to trigger each coil at the proper time. See CRANKSHAFT POSITION SENSOR under INPUT DEVICES. As with the C3I system, each cylinder is fired consecutively with the cylinder opposite it in the firing order. On V6, cylinder No. 1 is paired with 4, 2 with 5, and 3 with 6. On 4-cylinder, cylinder No. 1 is paired with 4 and cylinder No. 2 is paired with 3. Each pair of cylinders is fired by its own ignition coil.

On all models except Saturn, the crankshaft position sensor is mounted on the bottom of the DIS ignition module or near the ignition module. On Saturn, the crankshaft position sensor is mounted under the intake manifold. The sensor protrudes through the side of engine block to within .05" (1.3 mm) of an internally-mounted crankshaft reluctor ring. Sensor position is not adjustable.

The reluctor is a piece of metal, cast with the crankshaft. It has 7 slots machined into it, 6 of which are equally spaced (60 degrees apart). The seventh slot is spaced about 10 degrees from one of the other slots and generates a synchronization pulse signal. As crankshaft rotates, notches in the reluctor ring change the magnetic field at the tip of position sensor. This creates an induced AC voltage signal in the sensor windings, resulting in RPM reference signals which are sent to ECM by ignition module. This allows ECM to compute crankshaft position and RPM.