Ignition System: Description and Operation

Engine Ignition

The 4.0L SOHC ignition system consists of the:

- Crankshaft position sensor (CKP sensor) (6C315).
- Ignition coil (12029).
- Ignition wire and bracket (12280).
- Spark plugs (12405).

The ignition system is:

- An electronic distributorless ignition system (EDIS) controlled by an electronic engine control (EEC) integrated into the powertrain control module (PCM) (12A650).
- Set at 10 degrees before top dead center (BTDC) for base timing, and it is not adjustable.

Component Locations











The crankshaft position sensor:






- Is a variable reluctance sensor.
- Senses a missing tooth on crankshaft damper pulse ring.
- Generates a crankshaft position signal which is sent to the PCM. The PCM counts this signal for engine RPM.

The ignition coil:






- Changes low voltage pulses from the PCM to high voltage pulses.
- Has two transformers.

The spark plug wires:






- Carry high voltage pulses from the ignition coil to the spark plugs.

The spark plugs:






- Change high voltage pulses to spark at gap which ignites fuel and air mixture.
- Have a platinum enhanced active electrode for long life. The active electrode is different for LH and RH sides.
- Have replacements with both electrodes platinum enhanced so they can be used on either side.