STS AWD V8-4.6L VIN A (2006)
Variable Valve Timing Actuator: Description and Operation
CAMSHAFT ACTUATOR SYSTEM DESCRIPTION
The camshaft position (CMP) actuator system is used for a variety of engine performance enhancements. The CMP actuator system accomplishes this by
controlling the amount of intake and exhaust valve overlap. These enhancements include the following:
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Lower emission output through exhaust gas recirculation (EGR) control
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A wider engine torque range
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Improved gas mileage
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Improved engine idle stability
The CMP actuator system is comprised of the following components:
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Four CMP actuator solenoids
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Four oil control valves
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Four vane style CMP actuators
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Four CMP sensors
The CMP actuator system requires a very complex electrical signal from the engine control module (ECM) in order to control the position of the CMP
actuators. The electrical signal requires use of an un-fixed pulse width modulation (PWM) signal as well as 2 different operating frequencies of 150 and
500 Hz. Changes in the PWM can happen every 100 milliseconds and thus makes it difficult to measure the correct PWM or frequency with a DMM
during CMP actuator control. At idle, the ECM commands a consistent 7 percent duty cycle at 150 Hz. The ECM uses this signal in order to sense
certain circuit failures.
Camshaft Actuator Components
