Theory Of Operation

There are four Variable Valve Lift (VVL) Solenoids that control the operation of the Intake Rocker Arms for all six cylinders. See the figure and table below for the VVL Solenoid locations and cylinder control:

Courtesy of CHRYSLER GROUP, LLC

GENERAL OPERATION:  The VVL System is designed to vary the lift and duration of the Intake Valves, to maximize efficiency and engine torque, depending on engine operation. The VVL System consists of 2 step Intake Rocker Arms that are capable of operating in High Lift or Low Lift mode. The four VVL Solenoids control the Rocker Arm modes using engine oil pressure.

• Low Lift Mode:  The PCM commands the VVL Solenoids on, which supplies 12.0 volts to the VVL Solenoids and allows engine oil pressure to pass through the solenoids to the Rocker Arms. This in turn pushes the lock pins back which allows the center of the Rocker Arms to move down freely, allowing the Rocker Arms to operate in Low Lift Mode. It takes approximately 20.0 psi of engine oil pressure at the Rocker Arms to move the lock pins.
• High Lift Mode:  The Rocker Arms default to High Lift mode when no oil pressure is present. This is accomplished with a spring loaded lock pin that keeps the center of the Rocker Arms in the High Lift position. The Powertrain Control Module (PCM) commands the VVL Solenoids off when High Lift Mode is desired.

DIAGNOSTICS:  The PCM performs circuit diagnostics  on each VVL Solenoid High Side Driver (HSD) Circuit  for an open or short in the circuitry. If no circuit faults are detected, the PCM runs a rationality diagnostic  to check for any Rocker Arms that are stuck in the High Lift or Low Lift positions. The PCM can determine this by monitoring for an erratic MAP Sensor signal along with the Misfire, Knock and Individual Cylinder Fuel Control (ICFC) monitors to detect a Rocker Arm that is stuck in an incorrect position for a given cylinder. This diagnostic can also detect the mechanical failure of a solenoid or an oil pressure issue to one or more of the Rocker Arms. When a fault is detected for a Rocker Arm, the PCM will begin to record in field data  for diagnostic purposes until the PCM defaults the VVL system to High Lift or Low Lift mode. If the fault condition goes away during the next drive cycle the data collected will also be cleared.

• Low Lift stick condition:  If a single Rocker Arm is detected as being stuck in Low Lift Mode, the system will continue to operate normally and switch modes as desired. If more than one Rocker Arm is detected as being stuck in low lift mode, the PCM will default to commanding all of the Rocker Arms to low lift mode. Since the system can operate normally for an extended period with a Rocker Arm stuck in Low Lift before the system defaults to Low Lift Mode, the PCM is capable of collecting a large amount of data during fault detection.
• High Lift stick condition:  If any Rocker Arm is detected as being stuck in High Lift Mode, the PCM will quickly default to commanding all of the Rocker Arms to High Lift mode. Since the PCM quickly defaults to High Lift Mode, the PCM will collect only a small amount of data during fault detection.

When performing the VVL System Diagnostic test with the scan tool, the data collected from the in field diagnostics is factored in to help determine the source of the issue. Because of this, it is important not to disconnect the Battery or erase any DTCs or stored data prior to diagnosing the vehicle, as this info will be lost.  Some Rocker Arm stick conditions are more likely to be pinpointed during in field diagnostics while other conditions are more likely to be pinpointed during the scan tool test. See the table below for the best chance of detection and related diagnostic information.