Variable-valve-timing actuator
Variable-valve-timing actuator: A VVT cam phaser changes camshaft phase relative to the crank using oil pressure; an oil-control valve (OCV) can meter flow under ECU PWM control. The page also includes a worked example and measurement sequence.
Technical frame
Variable-valve-timing actuator: A VVT cam phaser changes camshaft phase relative to the crank using oil pressure; an oil-control valve (OCV) can meter flow under ECU PWM control. The page also includes a worked example and measurement sequence.
The technical values here expose the standard, protocol or physical relationship directly; model-specific service values are linked through the matching model/variant dossier.
The goal is not only to define the term but to let the reader calculate and interpret what the data means in a scan, scope or physical test.
Concrete technical facts
- A VVT cam phaser changes camshaft phase relative to the crank using oil pressure; an oil-control valve (OCV) can meter flow under ECU PWM control.
- Diagnosis compares desired cam angle with actual cam angle under the same engine speed, oil temperature and load.
- Low/wrong-viscosity oil, a restricted OCV screen, low oil pressure or mechanical phaser sticking can produce the same slow-response symptom.
- An OCV can work electrically while insufficient hydraulic flow prevents phase movement, so command and mechanical output are separate evidence.
- Crank/cam correlation reflects the combined result of chain/belt timing, phaser position and sensor reference.
- Confirm whether scan-tool angle is expressed in cam or crank degrees from the OEM data definition; in a four-stroke engine the camshaft rotates at half crankshaft speed.
Worked example
- Example: desired advance +20° and actual +5° gives a 15° tracking error. If OCV duty is high and oil pressure is low, investigate hydraulic supply first; with normal oil pressure, investigate OCV/phaser motion.
Measurement and verification sequence
- Record oil level/viscosity/temperature condition.
- Log desired/actual cam angle with OCV duty/current.
- Verify mechanical oil pressure at the correct test point.
- Separate crank/cam waveform and mechanical timing from phaser faults.
Fault-separation logic
- Is a valid command present and are power/ground/network healthy?
- Does feedback follow the command?
- Does an independent physical measurement confirm the output?
- Is the fault limited to a specific temperature/load/speed condition?
- Does the result remain stable when the original condition is repeated after repair?
Technical sources
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