CMP Actuator System Retard
WARNING: This page is about a different car, the 2003 Pontiac Vibe. However, it is still accessible from the selected car via links, so may be relevant.
When the oil flowing to the CMP actuator housing is from the CMP solenoid retard passage, oil pressure is applied to the retard side of the vane wheel. See Fig 1 . Because the solenoid advance passage is open, allowing oil pressure to decrease on the advance side of the vane wheel, 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. See CAMSHAFT PHASE COMMANDS table.
CAMSHAFT PHASE COMMANDS
| 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 |