On vehicles equipped with a conventional distributor, when the ignition switch is turned ON the battery voltage is applied to ignition coil primary winding. As the distributor shaft rotates, the igniter opens and closes the circuit repeatedly causing the ignition coil primary winding current to flow through the ignition coil negative terminal and igniter to ground or be interrupted.
The action induces high voltage in the ignition coil secondary winding. from the ignition coil, the secondary winding current produced flows through the distributor and spark plug to ground, thus causing ignition in each cylinder.
The 3.0L (24 valve) and 3.5L engines utilize a distributorless ignition system which is controlled by the Electronic Control Module (ECM). The ECM uses signals (electrical voltage pulses) from various components (i.e. crankshaft position sensor, throttle position sensor, etc.) to control the timing of the engine to match any conditions the engine is encountering. The crankshaft position sensor on the 3.0L (24 valve) engine is located down by the crankshaft under the timing belt cover. The crankshaft position sensor on the 3.5L engine is located under the upper left-hand timing belt cover secured to the cylinder head. Refer to Emission Controls for more indepth procedures of the individual components of this system.