Ignition Control: Overview Chrysler Pacifica CS

DESCRIPTION - IGNITION SYSTEM

Note. All engines use a fixed ignition timing system. Basic ignition timing is not adjustable. All spark advance is determined by the Powertrain Control Module (PCM).

The ignition system used on these engines is referred to as the Direct Ignition System (DIS). The system's four main components are the coils, crankshaft position sensor, spark plugs, and camshaft position sensor. If equipped with the coil on plug ignition system it utilizes an ignition coil for every cylinder and is mounted directly over the each spark plug.

OPERATION - IGNITION SYSTEM

The crankshaft position sensor and camshaft position sensor are hall effect devices. The camshaft position sensor and crankshaft position sensor generate 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 & camshaft position. For a description of both sensors, refer to Camshaft Position Sensor and Crankshaft Position Sensor.

DESCRIPTION

The coil capacitor is used for radio noise suppression

Scheme 1

1. Disconnect the negative battery cable.
2. Remove the electrical connector from capacitor.
3. Remove the bolt from capacitor. (Scheme 1)
4. Remove capacitor.

The knock sensor is attached to the cylinder block. The knock sensor is designed to detect engine vibration that is caused by detonation.

OPERATION

When the knock sensor detects a knock in one of the cylinders, it 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 material 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 as an input the knock sensor voltage signal. 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 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.

Note. Over or under tightening affects knock sensor performance, possibly causing improper spark control.

Scheme 2

Scheme 3

1. Disconnect the negative battery cable.
2. Remove the upper intake manifold. Refer to «REMOVAL - UPPER INTAKE MANIFOLD»(ref-245454-S10530475002006110200000).
3. Disconnect the electrical connector. (Scheme 2)
4. Remove the knock sensor. (Scheme 3)

Scheme 4

1. Disconnect the negative battery cable.
2. Raise vehicle and support.
3. Disconnect the electrical connector.
4. Remove mounting bolt (1). (Scheme 4)
5. Remove sensor.

Scheme 5

1. Install knock sensor. Tighten knock sensor to 20 N.m (15.2 in. lbs.) torque. Over or under tightening effects knock sensor performance, possibly causing improper spark control.
2. Route the knock sensor wire in the proper location. (Scheme 5)
3. Install the upper intake manifold. Refer to «INSTALLATION - UPPER INTAKE MANIFOLD»(ref-245454-S28311178522006110200000).
4. Connect the electrical connector. see scheme 28
5. Connect the negative battery cable.

DESCRIPTION - PLATINUM PLUGS

The V6 engines use platinum resistor spark plugs. They have resistance values of 6,000 to 20,000 ohms when checked with at least a 1000 volt tester. For spark plug identification and specifications, Refer to the SPECIFICATIONS .

Do not use an ohm meter to check the resistance of the spark plugs. This will give an inaccurate reading.

When the spark plug has a single or double platinum tip, the recommended service life for normal driving conditions per SCHEDULE A under MAINTENANCE SCHEDULES in Owner's Manual is 100,000 miles. The spark plugs have a recommended service life of 75,000 miles for severe driving conditions per SCHEDULE B under MAINTENANCE SCHEDULES in Owner's Manual. A thin platinum pad is welded to both or just the center electrode end(s) (Scheme 6) Extreme care must be used to prevent spark plug cross threading, mis-gapping and ceramic insulator damage during plug removal and installation. (Scheme 7)

Scheme 6

Scheme 7