Engine Control Module: Description and Operation
See Design and Function, Immobilizer.
Camshaft control (CVVT)
When the camshaft is set at the factory, it is aligned with the position of the crankshaft. The position of the camshaft in relation to the crankshaft is
designated the camshaft 0 position. During camshaft control (CVVT) the camshaft 0 position is offset. The value of the 0 position offset is called the cam
timing. The cam timing is 0° if the camshaft is not being controlled.
By controlling the cam timing (the camshaft is deployed from its 0 position) the performance of the engine is increased, the idle speed quality is
improved and the emissions are reduced.
In order to detect the cam timing, the engine control module (ECM) uses the signals from the engine speed (RPM) sensor (the position of the crankshaft)
and from the camshaft position (CMP) sensor (the position of the camshaft). By comparing these two signals, the control module is able to determine the
cam timing (the number of degrees the camshaft is from its 0 position).
There are diagnostic for this function. See also Camshaft diagnostics (CVVT) See: Powertrain Management/Computers and Control Systems/Description
and Operation/Camshaft Diagnostics (CVVT).
Camshaft cam timing