Automatic Wipe Mode
If the vehicle is equipped with the optional automatic wiper system, the rain/light sensor monitors an area within the wipe pattern of the windshield glass for the accumulation of moisture whenever the ignition switch is in the ON position. The RCM continually monitors the output of the rain/light sensor and sends the appropriate wipe command messages to the BCM. Depending upon the intensity of the precipitation monitored by the rain/light sensor, the front wiper system will be automatically operated in intermittent, continuous low or continuous high speed mode. When the control knob on the control stalk of the multi-function switch is moved to the I (Automatic) position, the SCM monitors this selection and sends an electronic wiper switch automatic message to the BCM. Based upon internal programming, the BCM operates the front wiper system accordingly.
The BCM logic is also programmed to provide an immediate initialization wipe cycle each time the control knob on the control stalk of the multi-function switch is moved from the 0 (Off) position to the I position while the ignition switch is in the ON position. This initialization wipe cycle is intended to clear the area of the windshield monitored by the rain/light sensor of moisture, dirt or debris to ensure accurate readings from the sensor. If the I position of the multi-function switch is already selected when the ignition switch is turned to the ON position, the initialization wipe cycle will not occur and the multi-function switch must be cycled manually to clear the glass over the sensor. Also, when the I position is selected with the multi-function switch but the automatic wipe feature has been disabled due to an ineffective circuit or component, the system will respond in the same manner as in the intermittent wipe mode on vehicles without the rain/light sensor.
The automatic wiper system also has features designed to protect the mechanical components of the wiper system, and will not allow automatic wiper operation under certain conditions. If the monitored ambient temperature is below 4° C (39° F) at the beginning of a new ignition cycle, the automatic wipers will not operate until the multi-function switch has been cycled, until a vehicle speed input greater than zero is detected, or until the monitored ambient temperature rises above 4° C (39° F).
The BCM logic is programmed to provide vehicle speed sensitivity to the automatic wipe mode. In order to provide this feature the BCM monitors electronic vehicle speed messages from the Antilock Brake System (ABS) module (also known as the Controller Antilock Brake/CAB, the Electronic Stability Program/ESP module, the ESP_SBC, or the ESP8) and automatically increases the intermittent delay interval, reduces the continuous wiper operating speed from high to low speed or from low to intermittent whenever the vehicle speed drops below about 5 kilometers-per-hour (3 miles-per-hour). The wiper speed automatically returns to the previous intervals or speed when the vehicle speed exceeds about 8 kilometers-per-hour (5 miles-per-hour).