Dodge Nitro. Manual — part 790

Fig. 12: Locating Ignition Coil - 3.7L
Courtesy of CHRYSLER LLC

3. Position ignition coil (1) into cylinder head opening and push onto spark plug. Do this while guiding coil

base over mounting stud.

4. Install coil mounting stud nut (2). Refer to Torque Specifications.

5. Connect electrical connector to coil by snapping into position.

6. If necessary, install throttle body air tube.

COIL-IGNITION - 4.0L

2007 Dodge Nitro R/T

2007 ENGINE Ignition Control - Service Information - Nitro

Fig. 13: Identifying Ignition Coil Electrical Connector, Coil Mounting Bolt & Ignition Coils
Courtesy of CHRYSLER LLC

1. Install ignition coil (3) into cylinder head.

2. Install and tighten coil mounting bolt (2). Refer to Torque Specifications.

3. Connect electrical connector (1) and lock.

4. Install upper half of intake manifold. Refer to INSTALLATION .

5. Connect negative battery cable.

6. Install engine cover.

SENSOR-KNOCK

OPERATION

OPERATION - 3.7L

Two knock sensors are used; one for each cylinder bank. When the knock sensor detects a knock in one of the
cylinders on the corresponding bank, it sends an input signal to the Powertrain Control Module (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
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

1 - Electrical Connector
2 - Mounting Bolt
3 - Coil

2007 Dodge Nitro R/T

2007 ENGINE Ignition Control - Service Information - Nitro

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.

OPERATION - 4.0L

Only one knock sensor is used. When the knock sensor detects a knock in one of the cylinders, it sends an input
signal to the Powertrain Control Module (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
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.

NOTE:

Over or under tightening the sensor mounting bolts will affect knock sensor
performance, possibly causing improper spark control. Always use the
specified torque when installing the knock sensors.

2007 Dodge Nitro R/T

2007 ENGINE Ignition Control - Service Information - Nitro

REMOVAL

SENSOR-KNOCK-3.7L

Fig. 14: Identifying Knock Sensors, Identification Tag (LEFT) & Electrical Connector
Courtesy of CHRYSLER LLC

The two knock sensors (1) are bolted into the cylinder block under the intake manifold. The two sensors share a
common wiring harness using one electrical connector (3). Because of this, they must be replaced as a pair.

1. Remove intake manifold. Refer to INSTALLATION .

2. Disconnect knock sensor dual pigtail harness from engine wiring harness. This connection is made near

rear of engine.

3. Remove both sensor mounting bolts. Note foam strip on bolt threads. This foam is used only to retain the

bolts to sensors for plant assembly. It is not used as a sealant. Do not apply any adhesive, sealant or
thread locking compound to these bolts.

4. Remove sensors from engine.

REMOVAL - 4.0L

NOTE:

Over or under tightening the sensor mounting bolt will affect knock sensor
performance, possibly causing improper spark control. Always use the
specified torque when installing the knock sensor.

NOTE:

The left sensor is identified by an identification tag (LEFT) (2). It is also
identified by a larger bolt head. The Powertrain Control Module (PCM) must
have and know the correct sensor left/right positions. Do not mix the sensor
locations.

2007 Dodge Nitro R/T

2007 ENGINE Ignition Control - Service Information - Nitro