Ignition Control System Dodge Grand Caravan IV

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

TORQUE

TORQUE SPECIFICATIONS

SPARK PLUG CABLE RESISTANCE

SPARK PLUG CABLE RESISTANCE SPECIFICATION 2.4L

SPARK PLUG CABLE RESISTANCE SPECIFICATION 3.3/3.8L

SPARK PLUG

SPARK PLUG GAP SPECIFICATION

Scheme 1

Scheme 2

DESCRIPTION

The relay is located in the Power Distribution Center (PDC). For the location of the relay within the PDC, refer to the PDC cover for location. Check electrical terminals for corrosion and repair as necessary.

OPERATION

The ASD sense circuit (SBEC vehicles) or the engine switched battery (NGC vehicles) informs the PCM when the ASD relay energizes. A 12 volt signal at this input indicates to the PCM that the ASD has been activated. This input is also used to power certain drivers on NGC vehicles.

When energized, the ASD relay on SBEC vehicles supplies battery voltage to the fuel injectors, ignition coils and the heating element in each oxygen sensor.

When energized, the ASD relay on NGC vehicles provides power to operate the injectors, ignition coil, generator field, O2 sensor heaters (both upstream and downstream), evaporative purge solenoid, EGR solenoid (if equipped) wastegate solenoid (if equipped), and NVLD solenoid (if equipped).

For both SBEC and NGC vehicles, the ASD relay also provides a sense circuit to the PCM for diagnostic purposes. If the PCM does not receive 12 volts from this input after grounding the control side of the ASD relay, it sets a Diagnostic Trouble Code (DTC). The PCM energizes the ASD any time there is an engine speed that exceeds a predetermined value (typically about 50 rpm). The ASD relay can also be energized after the engine has been turned off to perform an O2 sensor heater test, if vehicle is equipped with OBD II diagnostics.

As mentioned earlier, the PCM energizes the ASD relay during an O2 sensor heater test. This test is performed only after the engine has been shut off for SBEC vehicles. On NGC vehicles it checks the O2 heater upon vehicle start. The PCM still operates internally to perform several checks, including monitoring the O2 sensor heaters.

The camshaft position sensor for the 3.3/3.8L is mounted in the front of the timing case cover (Scheme 8) and the camshaft position sensor for the 2.4L is mounted on the end of the cylinder head (Scheme 5)

The camshaft position sensor provides cylinder identification to the Powertrain Control Module (PCM) (Scheme 3) The sensor generates pulses as groups of notches on the camshaft sprocket pass underneath it (Scheme 4) The PCM keeps track of crankshaft rotation and identifies each cylinder by the pulses generated by the notches on the camshaft sprocket. Four crankshaft pulses follow each group of camshaft pulses.

Scheme 3

Scheme 4

When the PCM receives 2 cam pulses followed by the long flat spot on the camshaft sprocket, it knows that the crankshaft timing marks for cylinder 1 are next (on driveplate). When the PCM receives one camshaft pulse after the long flat spot on the sprocket, cylinder number 2 crankshaft timing marks are next. After 3 camshaft pulses, the PCM knows cylinder 4 crankshaft timing marks follow. One camshaft pulse after the 3 pulses indicates cylinder 5. The 2 camshaft pulses after cylinder 5 signals cylinder 6 (Scheme 4) The PCM can synchronize on cylinders 1 or 4.

When metal aligns with the sensor, voltage goes low (less than 0.3 volts). When a notch aligns with the sensor, voltage switches high (5.0 volts). As a group of notches pass under the sensor, the voltage switches from low (metal) to high (notch) then back to low. The number of notches determine the amount of pulses. If available, an oscilloscope can display the square wave patterns of each timing event.

Top Dead Center (TDC) does not occur when notches on the camshaft sprocket pass below the sensor. TDC occurs after the camshaft pulse (or pulses) and after the 4 crankshaft pulses associated with the particular cylinder. The arrows and cylinder call outs on (Scheme 4) represent which cylinder the flat spot and notches identify, they do not indicate TDC position.

REMOVAL - 2.4L

The camshaft position sensor is mounted to the rear of the cylinder head.

Scheme 5

Scheme 6

1. Remove the negative battery cable.
2. Disconnect electrical connectors from the camshaft position sensor (Scheme 5)
3. Remove camshaft position sensor mounting screws. Remove sensor.
4. Loosen screw attaching target magnet to rear of camshaft and remove magnet (Scheme 6)

Scheme 7

Scheme 8

1. Disconnect the negative battery cable.
2. Remove the air box cover and inlet tube (Scheme 7)
3. Disconnect camshaft position sensor electrical connector from the wiring harness connector (Scheme 8)
4. Remove bolt holding sensor.
5. Rotate sensor away from block.
6. Pull sensor up out of the chain case cover. Do not pull on the sensor wiring. There is an O-ring on the body of the sensor. The O-ring may make removal difficult. A light tap to top of sensor prior to removal may reduce force needed for removal.

INSTALLATION - 2.4L

The target magnet has locating dowels that fit into machined locating holes in the end of the camshaft (Scheme 9)

Scheme 9

1. Install target magnet in end of camshaft. Tighten mounting screw to 3 N.m (30 in. lbs.) torque. Over torquing could cause cracks in magnet. If magnet cracks replace it.
2. Install camshaft position sensor. Tighten sensor mounting screws to 12.9 N.m (115 in. lbs.) torque.
3. Carefully attach electrical connector to camshaft position sensor.
4. Connect the negative battery cable.

INSTALLATION - 3.3/3.8L

If the removed sensor is reinstalled, clean off the old spacer on the sensor face. A NEW SPACER must be attached to the face before installation. Inspect O-ring for damage, replace if necessary. If the sensor is being replaced, confirm that the paper spacer is attached to the face and O-ring is positioned in groove of the new sensor (Scheme 10)

Scheme 10

1. Apply a couple drops of clean engine oil to the O-ring prior to installation.
2. Install sensor in the chain case cover and rotate into position.
3. Push sensor down until contact is made with the camshaft gear. While holding the sensor in this position, install and tighten the retaining bolt 14 N.m (125 in. lbs.) torque.
4. Connect camshaft position sensor electrical connector to harness connector.
5. Install the air box cover and inlet hose (Scheme 7)
6. Connect the negative battery cable.

The ignition coil assembly consists of 2 or 3 independent coils molded together (Scheme 11) or (Scheme 12) The coil assembly for the 3.3/3.8L is mounted on the intake manifold. The coil assembly for the 2.4L is mounted on the cylinder head cover. Spark plug cables route to each cylinder from the coil.

Scheme 11

Scheme 12

The coil fires two spark plugs every power stroke. One plug is the cylinder under compression, the other cylinder fires on the exhaust stroke. The Powertrain Control Module (PCM) determines which of the coils to charge and fire at the correct time.

The Auto Shutdown (ASD) relay provides battery voltage to the ignition coil. The PCM provides a ground contact (circuit) for energizing the coil. When the PCM breaks the contact, the magnetic energy in the coil transfers to the secondary causing the spark. The PCM will de-energize the ASD relay if it does not receive the crankshaft position sensor and camshaft position sensor inputs. Refer to AUTO SHUT DOWN RELAY for relay operation.

The electronic ignition coil pack attaches directly to the valve cover.

1. Disconnect the negative battery cable.
2. Disconnect electrical connector from coil pack
3. Remove coil pack mounting bolts.
4. Remove coil pack and heat shield (Scheme 11)

Scheme 13

1. Disconnect the negative battery cable.
2. Remove the throttle and speed control cables from clip.
3. Remove 2 bolts from the Power steering reservoir to intake manifold.
4. Loosen the lower nut for the power steering reservoir from stud on ignition coil bracket.
5. Reposition the Power steering reservoir (Scheme 13)
6. Remove the ignition cables from the ignition coil.
7. Disconnect the electrical connector from the ignition coil.
8. Remove 2 nuts from the ignition coil studs.
9. Remove 2 bolts from ignition coil, remove coil.

1. Install ignition coil and heat shield to valve cover and tighten bolts.
2. Connect the electrical connector to the ignition coil.
3. Transfer spark plug cables to new coil pack. The coil pack towers are numbered with the cylinder identification. Be sure the ignition cables are fully seated onto the towers.
4. Connect the negative battery cable.

1. Install coil over studs on bracket.
2. Install 2 bolts to ignition coil.
3. Install 2 nuts to the ignition coil studs. Tighten nuts and bolts.
4. Connect the electrical connector to the ignition coil.
5. Install the ignition cables to the ignition coil.
6. Reposition the Power steering reservoir. Slide bracket over the mounting stud (Scheme 13)
7. Install 2 bolts to the Power steering reservoir to intake manifold.
8. Tighten the lower nut to stud on ignition coil bracket.
9. Install the throttle and speed control cables to clip.
10. Connect the negative battery cable.

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

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.

The knock sensor threads into the side of the cylinder block in front of the starter (Scheme 14)

Scheme 14

1. Disconnect electrical connector from knock sensor.
2. Use a crow foot socket to remove the knock sensors.

REMOVAL - 3.8L

The knock sensor threads into the side of the cylinder block in the rear.

1. Disconnect the negative battery cable.
2. Raise vehicle and support.
3. On All Wheel Drive vehicles remove the PTU (Power Transfer Unit), refer to the appropriate Transmission article for more information.
4. Disconnect electrical connector from knock sensor.
5. Use a crow foot socket to remove the knock sensor.

The knock sensor threads into the side of the cylinder block in front of the starter (Scheme 14)

1. Install knock sensor. Tighten knock sensor to 10 N.m (7 ft. lbs.) torque. Over or under tightening effects knock sensor performance, possibly causing improper spark control.
2. Attach electrical connector to knock sensor.

INSTALLATION - 3.8L

The knock sensor threads into the side of the cylinder block in the rear.

1. Install knock sensor. Tighten knock sensor to 10 N.m (7 ft. lbs.) torque. Over or under tightening effects knock sensor performance, possibly causing improper spark control.
2. Attach electrical connector to knock sensor.
3. On All Wheel Drive vehicles install the PTU (Power Transfer Unit) for the rear wheels, refer to the appropriate Transmission article for more information.
4. Lower vehicle.
5. Connect the negative cable.

DESCRIPTION - STANDARD 4 CYLINDER

All engines use resistor spark plugs. They have resistance values ranging from 6,000 to 20,000 ohms when checked with at least a 1000 volt spark plug tester.

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

Refer to the SPARK PLUG for gap and type of spark plug.

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 plugs use a single or double platinum tips and they have a recommended service life of 100,000 miles for normal driving conditions per schedule A. The spark plugs have a recommended service life of 75,000 miles for severe driving conditions per schedule B. A thin platinum pad is welded to both or just the center electrode end(s) as shown in (Scheme 15) Extreme care must be used to prevent spark plug cross threading, mis-gapping (Scheme 16) and ceramic insulator damage during plug removal and installation.

Scheme 15

Scheme 16

REMOVAL

When replacing the spark plugs and spark plug cables, route the cables correctly and secure them in the appropriate retainers. Failure to route the cables properly can cause the radio to reproduce ignition noise, cross ignition of the spark plugs or short circuit the cables to ground.

Always remove cables by grasping at the boot, rotating the boot 1/2 turn, and pulling straight back in a steady motion.

1. Prior to removing the spark plug, spray compressed air around the spark plug hole and the area around the spark plug.
2. Remove the spark plug using a quality socket with a foam insert.
3. Inspect the spark plug condition.

INSTALLATION

When replacing the spark plugs and spark plug cables, route the cables correctly and secure them in the appropriate retainers. Failure to route the cables properly can cause the radio to reproduce ignition noise, cross ignition of the spark plugs or short circuit the cables to ground.

1. Coat threads of spark plug with anti-seize. Be sure not to get anti-seize ANYWHERE BUT ON THE THREADS OF THE SPARK PLUG as shown in (Scheme 15)
2. To avoid cross threading, start the spark plug into the cylinder head by hand.
3. Tighten spark plugs to 17.5 N.m (13 ft. lbs.) torque.
4. Install spark plug cables over spark plugs. A click will be heard and felt when the cable properly attaches to the spark plug.

Spark Plug cables are sometimes referred to as secondary ignition wires. The wires transfer electrical current from the ignition coil pack to individual spark plugs at each cylinder. The resistive spark plug cables are of nonmetallic construction. The cables provide suppression of radio frequency emissions from the ignition system.

Check the spark plug cable connections for good contact at the coil, and spark plugs. Terminals should be fully seated. The insulators should be in good condition and should fit tightly on the coil, and spark plugs. Spark plug cables with insulators that are cracked or torn must be replaced.

Clean Spark Plug cables with a cloth moistened with a non-flammable solvent. Wipe the cables dry. Check for brittle or cracked insulation. The spark plug cables and spark plug boots are made from high temperature materials.

REMOVAL - 2.0/2.4L

Failure to route the cables properly could cause the radio to reproduce ignition noise, cross ignition of the spark plugs or short circuit the cables to ground.

Remove spark plug cable from coil first.

Always remove the spark plug cable by grasping the top of the spark plug insulator, turning the boot 1/2 turn and pulling straight up in a steady motion.

INSTALLATION - 2.0/2.4L

Failure to route the cables properly could cause the radio to reproduce ignition noise, cross ignition of the spark plugs or short circuit the cables to ground. Install spark plug insulators over spark plugs. Ensure the top of the spark plug insulator covers the upper end of the spark plug tube, then connect the other end to coil pack.

See also:
• CAMSHAFT POSITION SENSOR
• SPARK PLUG