The microprocessor-based rain sensor module (1)
senses moisture in the wipe pattern (2) on the outside
of the windshield glass (3) and sends wipe commands
to the front control module (FCM). Four infrared
diodes within the sensor generate infrared light beams
that are aimed by four of the convex optical lenses
near the base of the sensor through the windshield
glass. Four additional convex optical lenses near the
top of the sensor are focused on the infrared light
beams on the outside of the windshield glass and
allow the four photocells within the sensor to sense
changes in the intensity of these infrared light beams.
When sufficient moisture accumulates within the wipe
pattern on the windshield glass, the sensor detects a
change in the monitored infrared light beam intensity.
The internal programming of the sensor then sends the appropriate electronic wipe command messages to the FCM
over the controller area network (CAN) data bus. The FCM responds by activating or deactivating the front wiper
system. The steering control module (SCM) sends electronic sensitivity level messages to the rain sensor module
over the CAN data bus based upon the driver-selected sensitivity setting of the control knob on the control stalk of
the right multi-function switch. The higher the selected sensitivity setting the more sensitive the rain sensor is to the
accumulated moisture on the windshield glass, and the more frequently the sensor will send wipe commands to the
FCM to operate the front wiper system.
The rain sensor module operates on battery current received through a fuse in the power distribution center (PDC)
on a fused B+ circuit. The rain sensor module receives ground at all times through the body wire harness. It is
important to note that the default condition of the automatic wiper system is low. Therefore, if no message is
received by the FCM from the rain sensor module for more than about five seconds when in the Auto sensitivity
wipe mode, the wipers will default to a constant low wipe state.
The rain sensor module ground and battery current inputs may be diagnosed using conventional diagnostic tools
and methods. The most reliable, efficient, and accurate means to diagnose the rain sensor module requires the use
of a scan tool and the appropriate diagnostic information.
8R - 46
FRONT WIPERS/WASHERS - SERVICE INFORMATION