Subaru Impreza 2002 Service Manual page 196

CAMSHAFT SPROCKET
MECHANICAL
C: INSPECTION
1) Check the sprocket teeth for abnormal wear and
scratches.
2) Make sure there is no free play between the
sprocket and key.
3) Check the crankshaft sprocket notch for sensor
for damage and contamination of foreign matter.
ME(STi)-57