Direct Ignition System (Dis)

DIS is a distributorless system used on 4.6L models. The operation of DIS is quite similar to operation of the C(3)I system. System consists of 4 (V8) ignition coils, ignition control module (located under coil pack), a camshaft position sensor, 2 Hall Effect crankshaft position sensors, necessary wiring, and the ignition control and fuel metering portion of the PCM.

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 C(3)I). This signal is received by PCM (through ignition control module) and is used to trigger each coil at the proper time. See CRANKSHAFT POSITION SENSOR under INPUT DEVICES. As with the C(3)I system, each cylinder is fired consecutively with the cylinder opposite it in the firing order. On V8, cylinder No. 1 is paired with No. 4, No. 2 with No. 5, No. 3 with No. 8 and No. 6 with No. 7. On V6, cylinder No. 1 is paired with No. 4, No. 2 with No. 5, and No. 3 with No. 6. On 4-cylinder, cylinder No. 1 is paired with No. 4 and cylinder No. 2 is paired with No. 3. Each pair of cylinders is fired by its own ignition coil.

On 4.6L, crankshaft position sensors ("A" and "B") are mounted on side of engine block between cylinders No. 4 and 6. The crankshaft position 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. On 4.6L, reluctor has 24 evenly spaced notches machined into it and an additional 8 unevenly spaced notches for a total of 32. As crankshaft rotates, notches in 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 PCM by the ignition control module. This allows PCM to compute crankshaft position and RPM.