Variable Camshaft Timing (VCT) Components

WARNING: This page is about a different variant/trim than selected.

NOTE: Left (Bank 2) installation shown, right (Bank 1) is similar.

ITEM	DESCRIPTION
1	Inlet Variable Camshaft Timing (VCT) actuator assembly
2	Exhaust Variable Camshaft Timing (VCT) actuator assembly
3	Exhaust Variable Camshaft Timing (VCT) solenoid
4	Camshaft Position (CMP) sensors
5	Inlet Variable Camshaft Timing (VCT) solenoid

The timing of the inlet and exhaust camshafts can be adjusted independently by an electro-hydraulic controlled VCT system. The Powertrain Control Module (PCM) controls the system using information from the Camshaft Position (CMP) sensors and the Crankshaft Position (CKP) sensor

The VCT system varies the timing of the intake and exhaust camshafts to deliver optimum engine power, efficiency and emissions. The timing of the intake camshafts has a range of 62 degrees of crankshaft angle. The timing of the exhaust camshafts has a range of 50 degrees of crankshaft angle.

In the base timing position:

The intake camshafts are fully retarded.
The exhaust camshafts are fully advanced.

Variable Camshaft Timing (VCT) Operating Ranges

CAMSHAFT	VALVE OPENS	VALVE CLOSES
Intake	33 degrees Before Top Dead Center (BTDC) to 29 degrees After Top Dead Center (ATDC)	197 to 259 ATDC
Exhaust	236 to 186 degrees BTDC	6 to 56 degrees ATDC

The system consists of a VCT unit and a VCT solenoid for each camshaft. The PCM controls the system using Pulse Width Modulation (PWM) signals to the VCT solenoids.

The torsional energy generated by the valve springs and the inertia of the valve train components are used to operate the system.

Variable Camshaft Timing (VCT) Units

The VCT units change the position of the camshafts in relation to the timing chains.

ITEM	DESCRIPTION
1	Bolt - 3 of
2	Variable Camshaft Timing (VCT) unit
3	Filter
4	CAMSHAFT
5	Inner plate
6	Housing and sprocket
7	Rotor assembly
8	Reed plate
9	Spring and lock pin
10	Spring - 3 of
11	Tip seal - 3 of
12	Spring - 2 of
13	Tip seal - 2 of
14	Spring
15	Dowel pin
16	Bias spring
17	Snap ring
18	Sensor wheel
19	Center plate
20	Snap ring
21	Bolt - 6 of
22	Spool valve
23	Outer plate

Each VCT unit is attached to the camshaft by three bolts. A rotor assembly and a reed plate are installed inside a sprocket housing, which consists of a sprocket, an outer plate and an inner plate held together by six bolts.

A sensor wheel, for the CMP sensor, a center plate and a bias spring are installed at the front of the VCT unit. The ends of the bias spring locate on the center plate assembly and the sprocket housing, to give a turning moment to the camshaft in the advance direction. A snap ring locates the sensor wheel on to a sleeve installed in the center of the rotor assembly. The opposite end of the sleeve locates in a bore in the front face of the camshaft, which contains a filter.

A spring and spool valve are installed in the rotor assembly sleeve and retained by a snap ring. The spring keeps the spool valve in contact with the armature of the related VCT solenoid.

Each VCT unit is supplied with engine oil from an oil gallery in the cylinder head, through the camshaft front bearing cap and a bore in the center of the camshaft.

Variable Camshaft Timing (VCT) Solenoids

The VCT solenoids control the position of the spool valves in the VCT units.

The VCT solenoids are installed in the front upper timing covers, immediately in front of their related VCT units. Each VCT solenoid is secured with two bolts and sealed with an O-ring. A two pin electrical connector provides the interface with the engine harness.

Each VCT solenoid incorporates a spindle that acts on the spool valve in the related VCT unit to advance and retard the camshaft timing. The VCT solenoids operate independently and are controlled by a PWM signal from the PCM.