Service manual

90-898303
4-15
2002 and Up 2.5L/3.0L Ignition System
Description
When the ignition key switch is turned to the ”RUN” position, battery voltage is
applied to both the Electronic Control Module (ECM) through the purple wire
and the main power relay through the red/purple wire. As the ECM receives
the ”RUN” signal, it internally completes the ground circuit of the main relay,
for a short period of time, energizing the fuel pump for start– up.
As the engine is cranked with the starter motor, the ECM receives the run
signal from the Crank Position Sensor (CPS) and completes the ground circuit
to the main relay for engine operation. With the main relay closed (completed
circuit), D.C. current from the battery/ charging system is transferred through
the 20 ampere main relay fuse to the positive terminal of all ignition coil
primary windings. The negative terminals of the ignition coil primaries are
connected to engine ground through the coils’ internal driver, which is
triggered by the ECM.
With the coil drivers closed, a electric magnetic field is allowed to build up
within the ignition coil. As the flywheel rotates, the CPS senses the location of
the 54 teeth on the flywheel and supplies the trigger signal information to the
ECM. The ECM utilizes the CPS information and determines when to remove
the trigger signal from the coil driver of each ignition coil. The coil driver then
opens the coil primary ground circuit, allowing it’s magnetic field to rapidly
collapse across the coil secondary winding, which induces a high voltage
charge (50,000 volts) that fires the spark plug.
Notes
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