Operation
The PCM operates the CMP actuator solenoid valve by pulse width modulation (PWM) of the solenoid coil. The higher the PWM duty cycle, the larger the change in camshaft timing. Oil pressure that is applied to the advance side of the fixed vanes will rotate the camshaft in a clockwise direction. The clockwise movement of the camshaft will advance the timing up to a maximum of 21 degrees. When oil pressure is applied to the return side of the vanes, the camshaft will rotate counterclockwise until returning to 0 degrees.
Scheme 42
| Callout | Component Name |
|---|---|
| 1 | Vane Wheel |
| 2 | CMP Actuator Housing, part of CMP actuator assembly |
| 3 | Intake Camshaft Gear, part of CMP actuator assembly |
| 4 | Intake Camshaft |
| 5 | Advance Side Oil Passage, applying pressure |
| 6 | CMP Actuator Solenoid Valve |
| 7 | Retard Side Oil Passage, relieving pressure |
Oil flowing to the CMP actuator housing (2) from the CMP solenoid advance passage (5) applies pressure to the advance side of the vane wheel (1) in the CMP actuator assembly. At the same time the CMP solenoid retard passage (7) is open, allowing oil pressure to decrease on the retard side of the vane wheel. These two simultaneous actions cause the vane wheel (1) to rotate clockwise, advancing camshaft advance timing.
Scheme 43
| Callout | Component Name |
|---|---|
| 1 | Vane Wheel |
| 2 | CMP Actuator Housing, part of CMP actuator assembly |
| 3 | Intake Camshaft Gear, part of CMP actuator assembly |
| 4 | Intake Camshaft |
| 5 | Advance Side Oil Passage, relieving pressure |
| 6 | CMP Actuator Solenoid Valve |
| 7 | Retard Side Oil Passage, applying pressure |
When the oil flowing to the CMP actuator housing (2) is from the CMP solenoid retard passage (7), oil pressure is applied to the retard side of the vane wheel (1). Because the solenoid advance passage (5) is open, allowing oil pressure to decrease on the advance side of the vane wheel (1), the camshaft position retards.
The PCM can also command the CMP actuator solenoid valve to stop oil flow from both passages in order to hold the current camshaft position. The PCM is continuously comparing CMP sensor input with CKP sensor input in order to monitor camshaft position and detect any system malfunctions. The following table provides camshaft phase commands for common driving conditions
| Driving Condition | Change in Camshaft Position | Objective | Result |
|---|---|---|---|
| Idle | No Change | Minimize Valve Overlap | Stabilize Idle Speed |
| Light Engine Load | Retard Valve Timing | Decrease Valve Overlap | Stable Engine Output |
| Medium Engine Load | Advance Valve Timing | Increase Valve Overlap | Better Fuel Economy with Lower Emissions |
| Low to Medium RPM with Heavy Load | Advance Valve Timing | Advance Intake Valve Closing | Improve Low to Mid-range Torque |
| High RPM with Heavy Load | Retard Valve Timing | Retard Intake Valve Closing | Improve Engine Output |
CMP Actuator System Operation