Ignition System - Service Information: Overview RAM Pickup 2500

OPERATION

The coil capacitor(s) help dampen the amount of conducted electrical noise to the camshaft position sensor, crankshaft position sensor, and throttle position sensor. This noise is generated on the 12V supply wire to the ignition coils and fuel injectors.

DESCRIPTION

Two knock sensors are bolted into the cylinder block under the intake manifold 3.7L .

The knock sensor is bolted to the cylinder block under the intake manifold 4.7L .

Two knock sensors are also used with the 5.7L . These are bolted into each side of the cylinder block (outside) under the exhaust manifold.

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 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.

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.

Scheme 1

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.

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.

1. Remove intake manifold. Refer to «REMOVAL»(ref-457795-S41183631432012030200000) .
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.

Scheme 2

Scheme 3

1. Remove the intake manifold. Refer to «REMOVAL»(ref-457796-S33174645932012030200000) .
2. Remove the knock sensor retaining bolt and remove the knock sensor (1).
3. Disconnect the knock sensor electrical connector (1) from the engine harness located at the back of engine by pressing on the connector lock tab (2).
4. Thoroughly clean the knock sensor mounting hole.

Scheme 4

Two knock sensors (1) are used. Each sensor is bolted to the outside of the cylinder block below the exhaust manifold(s) (3).

1. Raise and support the vehicle.
2. Disconnect the knock sensor electrical connector(s) (5).
3. Remove the knock sensor retaining bolt(s) (2). NOTE: Note the foam strip on bolt threads. This foam strip is used only to retain the bolts to the 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 the knock sensor(s) (1) from the cylinder block.

This vehicle is equipped with a Wireless Ignition Node (WIN). The WIN, along with the FOB with Integrated Key (FOBIK) are the primary components of the keyless ignition system. The only visible component of the WIN is the ignition switch located on the face of the instrument panel just to the inboard side of the steering column. The remainder of the WIN including its mounting provisions and electrical connections are concealed within the instrument panel.

In addition to replacing a conventional keyed ignition switch, the WIN is an integrated electronic receiver that serves as the base station in the vehicle. It communicates with other electronic modules in the vehicle over the Controller Area Network (CAN) data bus.

The WIN interfaces with the Remote Keyless Entry (RKE) FOBIK and the Tire Pressure Monitor (TPM) sensors (if equipped) using Radio Frequency (RF) communication, with the Sentry Key Immobilizer System (SKIS) transponder within the FOBIK using Low Frequency (LF) RF communication.

The WIN cannot be adjusted or repaired, but is flash update capable. If ineffective or damaged the entire WIN must be replaced. Refer to RECEIVER, Wireless Ignition Node , Removal and RECEIVER, Wireless Ignition Node , Installation .