XC70 L5-2.5L Turbo VIN 59 B5254T2 (2003)
The reference positions of the crankshaft coincide exactly with each camshaft flank if the camshaft cam timing is 0 degree. If the cam timing deviates
from 0 degree, i.e. the flanks deviate from the reference positions of the crankshaft, the control module calculates the number of crankshaft degrees by
which the flank is deviating.
The control module detects the reference positions for the camshaft flanks using the signal from the engine speed (RPM) sensor.
Example:
If camshaft flank 1 is detected at 10 degree from the crankshaft reference position for flank 1 (0 degree +10 degree), the cam timing is 10 degree. If the
cam timing is the same (10 degree), flank 2 is detected at 216 degree (206 degree + 10 degree), flank 3 at 396 degree (386 degree + 10 degree), and
flank 4 at 586 degree (576 degree + 10 degree). The cam timing can be positive (+) or negative (-) depending on whether the flank is detected before or
after the different reference positions for the crankshaft.
The engine control module (ECM) controls the camshaft reset valve smoothly in order to regulate the camshaft cam timing. The valve controls the flow
of engine oil to the continuous variable valve timing (CVVT) unit which is affected by the oil pressure that builds up.
Also see Design.
Control
