Description And Operation

DESCRIPTION 

Courtesy of CHRYSLER GROUP, LLC

The ignition control system contains the following components:

1. Ignition Coil  - Spark Plugs are not shown. They are located below each ignition coil.
2. Camshaft Position Sensor 
3. Powertrain Control Module (PCM) 
4. Knock Sensor 
5. Ignition Noise Capacitor 

• Glow Plug - DIESEL APPLICATIONS ONLY  not shown

This engine uses a fixed ignition timing system. Basic ignition timing is not adjustable. All spark advance is determined by the PCM.

The ignition system is referred to as coil on plug. The coil on plug ignition system utilizes an ignition coil for every cylinder. The ignition coils are mounted directly over each spark plug.

OPERATION 

The crankshaft position sensor and camshaft position sensor are hall effect devices. The camshaft position sensor and crankshaft position sensor generate square wave pulses that are inputs to the PCM. The PCM determines engine position from these sensors. The PCM calculates injector sequence and ignition timing from crankshaft and the camshaft position.

Camshaft Position Sensor  - A current-carrying semiconductor layer immersed in a normal magnetic field (force lines at right angles to current direction) generates a potential difference known as a Hall voltage at its terminals. If current intensity remains constant, the generated voltage depends on magnetic field intensity alone. Periodic changes in magnetic field intensity are sufficient to generate a modulated electrical signal with frequency proportional to the speed of magnetic field change. The distance between the sensor and the surface of the timing wheel on the cam axis is altered to produce this change.

Glow Plug  - The glow plugs are used in diesel engines to preheat the combustion chambers in order to achieve the ignition temperature required for the fuel-air mixture.

The heating element is integrated in the glow rod. It consists of a heating winding and a control winding connected in series.

The glow plug system is a quick start type. This allows for immediate start in practically all weather conditions without long periods of pre-glowing; this works in conjunction with the diesel fuel injectors.

Ignition Coil 

• The Auto Shutdown (ASD) relay provides battery voltage to the ignition coil.
• The PCM provides a ground path with an internal Low Side Driver (LSD).
• When the PCM opens the LSD, the ground path is broken and the energy in the coil primary.
• The PCM will de-energize the ASD relay if it does not receive the crankshaft position sensor and camshaft position sensor inputs

The spark plugs have resistance values of 3, 000 to 16, 000 ohms when checked with at least a 1000 volt tester. For spark plug identification and specifications. Refer to TECHNICAL SPECIFICATIONS .

Knock Sensor  - The knock sensor:

• detects a knock in one of the cylinders on the corresponding bank
• sends an input signal to the PCM

In response, the PCM retards ignition timing for all cylinders by a scheduled amount.

Knock sensors contain a piezoelectric crystal which constantly vibrates and sends an input voltage (signal) to the PCM while the engine operates. As the intensity of the crystal's vibration increases, the knock sensor output voltage also increases.

The voltage signal produced by the knock sensor increases with the amplitude of vibration. The PCM receives the knock sensor voltage signal as an input. If the signal rises above a predetermined level, the PCM will store that value in memory and retard ignition timing to reduce engine knock. If the knock sensor voltage exceeds a preset value, the PCM retards ignition timing for all cylinders. It is not a selective cylinder retard.

The PCM ignores knock sensor input during engine idle conditions. Once the engine speed exceeds a specified value, knock retard is allowed.

Knock retard uses its own short term and long term memory program.

Long term memory stores previous detonation information in its battery-backed RAM. The maximum authority that long term memory has over timing retard can be calibrated.

Short term memory is allowed to retard timing up to a preset amount under all operating conditions (as long as RPM is above the minimum RPM) except at Wide Open Throttle (WOT). The PCM, using short term memory, can respond quickly to retard timing when engine knock is detected. Short term memory is lost any time the ignition key is turned off.

Powertrain Control Module  - The PCM adjusts ignition timing based on the following inputs:

• Coolant Temperature
• Intake Air Temperature
• Engine Speed (Crankshaft Position Sensor)
• Manifold Absolute Pressure
• Mass Airflow Sensor
• Throttle Position Sensors and Pedal Value Sensors

Spark Plug 

• mounted below each coil-on-plug assembly
• Platinum/iridium (dual precious metal)
• long-life service of 100, 000 miles
• accessed by:
  • removing the coil-on-plug on the right bank
  • removing the upper intake manifold assembly to access and remove the coil-on-plug on the left bank.