Subaru 2002 Impreza Service Manual page 73

SENSORS AND SWITCHES
Fuel Injection (Fuel Svstem)
F: CAMSHAFT POSITION SENSOR
0
The camshaft position sensor is located on the left-hand camshaft support. It detects the com-
bustion cylinder at any given moment.
0
The sensor generates a pulse when one of the bosses on the back of the left-hand camshaft
drive sprocket passes in front of the sensor. The ECM determines the camshaft angular position
by counting the number of pulses.
Internal construction and the basic operating principle of the camshaft position sensor are similar
to those of the crankshaft position sensor. Two bosses are provided on the sprocket as shown be-
low.
(1) Boss
(2) Camshaft sprocket
(3) Air gap
NF0478
(4) Camshaft
position sensor
(5) Camshaft one rotation (Crankshaft two rotations)
FU-23