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303-14-46 Powertrain Control Management 303-14-46 DESCRIPTION AND OPERATION (Continued) 3. Check the harness for open circuits and short The camshaft timing is controlled by directing oil circuits. under pressure (from the engine oil pump) into one of two ports in the Phaser, one port will retard the cam 4. Further testing of EDF1-2 is described in Section timing (‘Retard port’) and the other will advance the 303-03, Engine Cooling. timing (‘Advance port’). An Oil Control Valve (OCV), Variable Camshaft Timing one for each camshaft is used to control the flow of oil into the retard and advance ports of both cams. The I6 Engine OCV is controlled by the PCM. The I6 Engine is fitted with variable inlet and exhaust The PCM uses a pulse width modulated (PWM) camshaft timing. Both camshafts are variable over a voltage or ‘Duty Cycle’ (DC) to control each OCV to 60-degree crank angle. This is achieved by two attain the desired camshaft angle. VCT1 output separate hydraulic mechanisms called ‘Phasers’, controls the Bank1 camshaft OCV. VCT2 controls the which are integral with the intake and exhaust Bank2 camshaft OCV. camshaft drive sprockets. A 4 + 1 tooth wheel on the front of each camshaft with The camshaft timing is controlled by directing oil an associated sensor mounted on the intake and under pressure (from the engine oil pump) into one of exhaust sides of the cylinder head are used to two ports in the Phaser, one port will retard the cam calculate the ‘Actual cam angle’ for both camshafts. timing (‘Retard port’) and the other will advance the The two sensors, CID1 and CID2 measure the timing (‘Advance port’). An Oil Control Valve (OCV), camshaft angle on Bank 1 and Bank2 respectively. one for each camshaft is used to control the flow of oil The PCM uses engine rpm, throttle position and into the retard and advance ports of both cams. The engine load to determine the optimum camshaft OCV is controlled by the PCM. timing setting or ‘Desired Cam Angle’ for both The PCM uses a pulse width modulated (PWM) camshafts. voltage or ‘Duty Cycle’ (DC) to control each OCV to Once the PCM has determined the Desired Cam attain the desired camshaft angle. VCT1 output Angle, it will control the Duty Cycle output VCT1 and controls the inlet camshaft OCV. VCT2 controls the VCT2, to the intake and exhaust OCVs based on the exhaust camshaft OCV. difference between the Desired Cam Angle and the A 3 + 1 tooth wheel on the front of each camshaft with Actual Cam Angle. This difference is called the Cam an associated sensor mounted on the intake and Angle Error. The Cam Angle Error for each cam is exhaust sides of the cylinder head are used to calculated individually and used to control both calculate the ‘Actual cam angle’ for both camshafts. camshafts independently to a single Desired Cam The two sensors are called, intake cam position or Angle. ‘CID1’ and exhaust cam position or ‘CID2’. Intake and An engine oil temperature sensor, which measures oil exhaust cam positions are calculated separately. temperature in the oil sump, is used to compensate The PCM uses engine rpm, throttle position and for Phaser response with changing oil viscosity at engine load to determine the optimum camshaft different temperatures. timing setting or ‘Desired Cam Angle’ for both Modes of Operation camshafts. 1. Start-Up Mode Angle, it will control the Duty Cycle output VCT1 and In this mode the VCT phasers will be in the fully VCT2, to the intake and exhaust OCVs based on the advanced position or locked position. The Camshafts difference between the Desired Cam Angle and the are locked mechanically by a hydraulic ‘Locking Pin’ Actual Cam Angle. This difference is called the Cam which forms part of the phaser. The VCT1 and VCT2 Angle Error. The Cam Angle Error for each cam is duty cycle sent to the oil control valves will be 0%. calculated individually and used to control both Exit from startup mode is within 10 seconds of camshafts independently to a single Desired Cam starting. Angle. temperature in the oil gallery of the engine block, is At idle, the VCT Phasers are in the locked fully used to compensate for Phaser response with advance position as per Start-Up Mode. Exit from Idle changing oil viscosity at different temperatures. Mode occurs when the engine speed is above 1,050 RPM and the throttle is open. 5.4 L, 3 Valve V8 Engine The 5.4, 3V, V8 Engine is fitted with variable inlet and 3. Normal Drive Mode exhaust camshaft timing on each cylinder head bank . In this mode of operation the camshaft timing angle is The camshaft on each bank is variable over a controlled to a Desired Cam Angle which is 60-degree crank angle using two separate hydraulic determined by, Engine Speed, Engine Load, Throttle ‘Phasers’, which are integral with the Bank1 and Position. In this condition the PCM VCT1 and VCT2 Bank2 camshaft drive sprockets. output duty cycle will be between 20% and 80% (0.2 G98133 en |