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:
| VVL SOLENOID | PHYSICAL LOCATION | CYLINDERS CONTROLLED | RELATED FAULT CODES |
|---|---|---|---|
| VVL SOLENOID 1/1 | BANK 1 FRONT SOLENOID | CYLINDER 1 INTAKE VALVES | P1050 / P1051 / P1052 / P1070 |
| VVL SOLENOID 1/2 | BANK 1 REAR SOLENOID | CYLINDERS 3 AND 5 INTAKE VALVES | P1053 / P1054 / P1055 / P1071 |
| VVL SOLENOID 2/1 | BANK 2 FRONT SOLENOID | CYLINDER 2 INTAKE VALVES | P1056 / P1057 / P1058 / P1072 |
| VVL SOLENOID 2/2 | BANK 2 REAR SOLENOID | CYLINDERS 4 AND 6 INTAKE VALVES | P1059 / P105A / P105B / P1073 |
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 controls each VVL Solenoid with a High Side Driver (HSD) Circuit . The PCM performs circuit diagnostics on each VVL Solenoid HSD for an open or short in the circuitry.
Typical High Side Driver and Fault Detection: This type of driver circuit is generally used for relay control, controlling a solenoid or a similar type of driver device. The PCM provides 12 volts to operate the device when switched on. The PCM also provides fault detection for the device, wiring and internal driver. In the example below, the PCM uses an internal pull up diagnostic resistor and calibrated voltage reference (V-Ref) as a comparator for fault detection.
- Circuit Open and Circuit High Detection: The PCM monitors for an open circuit and short to voltage when the internal driver is switched off. A small amount of amperage is provided to the device through the internal pull up diagnostic resistor connected in series with the device. The diagnostic voltage is monitored between the pull up resistor and device, and compared to V-Ref. If the resistance in the device or circuitry becomes too large (approaches open) the voltage supply will increase on the comparator circuit and become greater than V-Ref, and a fault is detected. A short to Battery voltage will have the same effect.
- Circuit Low Detection: The PCM monitors for a short to ground when the driver is turned on. When switched on, the voltage to the device should be close to the 12 volt supply voltage. A short to ground will pull the voltage at the comparator circuit below V-Ref and a circuit low fault is detected.