Jeep Cherokee

 Service Manual

Ignition system » Description and operation
Ignition system

DESCRIPTION

Two different ignition systems are used. One type is used for the 2.5L 4-cylinder engine. The other is used for the 4.0L 6-cylinder engine.

OPERATION

2.5L 4-Cylinder Engine:

The ignition system is controlled by the Powertrain Control Module (PCM).

The ignition system consists of:

•  Spark Plugs
•  Ignition Coil
•  Secondary Ignition Cables
•  Distributor (contains rotor and camshaft position sensor)
•  Powertrain Control Module (PCM)
•  Crankshaft Position, Camshaft Position, Throttle Position and MAP Sensors

4.0L 6-Cylinder Engine:

The 4.0L 6-cylinder engine uses a one-piece coil rail containing three independent coils. Although cylinder firing order is the same as 4.0L engines of previous years, spark plug firing is not. The 3 coils dualfire the spark plugs on cylinders 1-6, 2-5 and/or 3-4.

When one cylinder is being fired (on compression stroke), the spark to the opposite cylinder is being wasted (on exhaust stroke). The one-piece coil bolts directly to the cylinder head. Rubber boots seal the secondary terminal ends of the coils to the top of all 6 spark plugs. One electrical connector (located at the rear end of the coil rail) is used for all three coils.

Because of coil design, spark plug cables (secondary cables) are not used on either engine. A distributor is not used with the 4.0L engine.

The ignition system is controlled by the Powertrain Control Module (PCM).

The ignition system consists of:

•  Spark Plugs
•  Ignition Coil(s)
•  Powertrain Control Module (PCM)
• Crankshaft Position Sensor
•  Camshaft Position Sensor
•  The MAP, TPS, IAC and ECT also have an effect on the control of the ignition system.

Ignition system

Distributor-2.5L engine

Spark plugs

Spark plug cables-2.5L engine

Ignition coil-2.5L engine

Ignition coil-4.0L engine

Crankshaft position sensor

Camshaft position sensor-2.5L engine

Camshaft position sensor-4.0L engine

Ignition switch and key lock cylinder