Variable Camshaft Timing (VCT) System: Overview

WARNING: This page is about a different car, the 2011 Mercury Milan, 2011 Lincoln MKZ, 2011 Ford Fusion, 2010 Mercury Milan, and 2010 Ford Fusion. However, it is still accessible from the selected car via links, so may be relevant.

The intake phase shifting (IPS) VCT system enables rotation of the intake camshaft relative to the crankshaft rotation as a function of engine operating conditions.

The VCT system has several operational modes: idle, part throttle, wide open throttle (WOT), and default mode. At idle and low engine speeds with closed throttle, the powertrain control module (PCM) determines the phase angle based on a constant angle, limited by engine oil temperature and engine RPM. At part and wide open throttle the PCM determines the phase angle based on engine RPM, load, and throttle position. VCT systems provide reduced emissions and enhanced engine power, fuel economy and idle quality. IPS systems also have the added benefit of improved torque.

The VCT system knocking and noise concerns are diagnosed in the appropriate service information. For additional information, refer to the ENGINE SYSTEM - GENERAL INFORMATION -- FUSION, MILAN & MKZ . Verification of incorrect VCT phasing on a warm engine operating below 1500 RPM can be isolated using a stethoscope and by monitoring the VCTADV, VCTADVERR and VCTDC PIDs using a scan tool. If the VCT phaser does not maintain correct valve timing, low oil pressure or oil flow restrictions are primary possible causes. Verify correct oil pressure and flow, refer to the ENGINE SYSTEM - GENERAL INFORMATION -- FUSION, MILAN & MKZ .

PID DESCRIPTION CHART

PID	Description
VCTADV	Monitors the VCT advance and displays the advance angle in degrees. The actual camshaft position is measured using the camshaft position (CMP) sensor.
VCT1_F	Displays FAULT or NO FAULT to indicate a VCT related concern is detected. The CMP circuit DTCs cause the VCT advance to default to 0. Correct any CMP DTCs prior to diagnosing engine timing or VCT DTCs.
VCTADVERR	Displays the error in VCT advance. VCTADVERR uses the CMP signal to determine the difference between the actual camshaft position and the camshaft advance requested. The difference is displayed as a percentage that ranges from -5 to +5 %. When the accelerator pedal is cycled this may range as high as 20 %.
VCTDC	Variable camshaft timing duty cycle ranges from 0 to 100%. The PCM controls the VCT solenoid operation through the duty cycled ground.
VCTSYS	Variable camshaft timing system displays whether the engine is in open or closed loop. In open loop, the PCM defaults the VCT system to off (0% duty cycle). In closed loop, the PCM turns the VCT system to ON (varies the VCT duty cycle). If a VCT DTC is detected, the VCT system defaults to open loop operation.