The Variable Valve Timing (VVT) system includes the ECM, camshaft timing oil control valve assembly and VVT controller. The ECM sends a
target duty-cycle control signal to the camshaft timing oil control valve assembly. This control signal regulates the oil pressure supplied to the VVT
controller. Camshaft timing control is performed according to engine operating conditions such as the intake air volume, throttle valve position and
engine coolant temperature. The ECM controls the camshaft timing oil control valve assembly, based on the signals transmitted by several sensors.
The VVT controller regulates the exhaust camshaft angle using oil pressure through the camshaft timing oil control valve assembly. As a result, the
relative positions of the camshaft and crankshaft are optimized, the engine torque and fuel economy improve, and the exhaust emissions decrease
under overall driving conditions. The ECM detects the actual exhaust valve timing using signals from the camshaft and crankshaft position sensors,
and performs feedback control. This is how the target intake valve timing is verified by the ECM.
MONITOR DESCRIPTION
The ECM checks valve timing (VVT learning value) on the exhaust side while the engine is running at a low speed, in order to monitor the gap
between the current and target valve timing on the exhaust side. The VVT learning value is calculated from the positions of the camshaft and
crankshaft. The camshaft will come to the most retarded position when the engine is running at a low speed. If the camshaft position is normal, the
VVT learning value should be within the specified range. If the VVT learning value is not within the specified range, the ECM determines this as a
malfunction.
MONITOR STRATEGY
TYPICAL ENABLING CONDITIONS
TYPICAL MALFUNCTION THRESHOLDS
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