2.0L Ignition System (Service Information): Operation

Camshaft Position (CMP) Sensor 

This engine uses a Dual Over Head Camshaft (DOHC) configuration. Each camshaft has a pressed on ferrous timing wheel with a shape that can be read by the CMP sensor to indicate the position and speed of each camshaft. The CMP sensors are mounted on each side of the engine, placed in order to read each timing wheel.

The Crankshaft Position (CKP) sensor and CMP sensor are hall effect devices. The CMP and CKP sensors generate square wave pulses that are inputs to the Powertrain Control Module (PCM). The PCM determines engine position from these sensors. The PCM calculates injector sequence and ignition timing from crankshaft and camshaft position.

Knock Sensor 

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.

Courtesy of CHRYSLER GROUP, LLC

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 crystals 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 Random Access Memory (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.

Variable Valve Timing (VVT) 

Camshaft phaser position is adjusted using regulated oil pressure through an Oil Control Valve (OCV). To begin Phaser movement, the PCM applies a pulse-width modulated voltage signal to the VVT solenoid to extend or retract the solenoid pintle. The pintle pushes against an internal spool valve within the OCV moving the valve forwards and backwards to direct oil flow. The position of the spool inside the OCV determines which ports and chambers inside the phaser are being fed, either to advance the timing of the phaser sprocket relative to the camshaft, retard it, or hold a desired position.