Rear

REAR





The rear wiper and washer system is designed to provide the vehicle operator with a convenient, safe, and reliable means of maintaining visibility through the rear door glass. The various components of this system are designed to convert electrical energy produced by the vehicle electrical system into the mechanical action of the wiper blades to wipe the outside surface of the glass, as well as into the hydraulic action of the washer system to apply washer fluid stored in an on-board reservoir to the area of the glass to be wiped. When combined, these components provide the means to effectively maintain clear visibility for the vehicle operator by removing excess accumulations of rain, snow, bugs, mud, or other minor debris from the outside rear door glass surface that might be encountered while driving the vehicle under numerous types of inclement operating conditions.

Two rear wiper systems are available: The standard intermittent wipe system, or an optional automatic wipe system. The vehicle operator initiates all rear wiper and washer system functions with the controls on the end of the multi-function switch control stalk that extends from the left side of the steering column, just below the steering wheel. Rotating the control sleeve on the control stalk to the detent positions marked on the fixed band of the stalk selects the 0 (Off) or I (Intermittent) rear wiper system operating modes, while rotating the sleeve to the momentary upward position from 0 or momentary downward position from I selects rear washer system operation.

Rear wiper and washer system operation is completely controlled by the Body Control Module (BCM) (also known as the Signal Acquisition and Actuation Module/SAM) logic circuits based upon electronic wipe command and wash commandmessage inputs received from the Steering Control Module (SCM) (also known as the steering column module/MRM) based upon the selected multi-function switch position and, on vehicles so equipped, from the Roof Control Module (RCM) (also known as the Overhead Control Panel/OCP control unit or DBE) based upon inputs received from the rain/light sensor. The BCM will only allow these systems to operate when the ignition switch is in the ON position. The BCM also uses inputs from the backup lamp switch and the two rear door ajar switches for rear wiper system control. The BCM uses high side drivers to control wiper system operation by energizing or de-energizing the rear wiper relays integral to the rear wiper motors, and a low side driver to control the rear washer pump/motor unit.

The hard wired circuits and components of the rear wiper and washer system may be diagnosed using conventional diagnostic tools and procedures. Refer to the appropriate wiring information. However, conventional diagnostic methods will not prove conclusive in the diagnosis of the rear wiper and washer system or the electronic controls or communication between other modules and devices that provide some features of the rear wiper and washer system. The most reliable, efficient, and accurate means to diagnose the rear wiper and washer system or the electronic controls and communication related to rear wiper and washer system operation requires the use of a diagnostic scan tool. Refer to the appropriate diagnostic information.

OPERATING MODES

Following are paragraphs that briefly describe the operation of each of the rear wiper and washer system operating modes.

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.

If the front wiper system control knob on the control stalk of the multi-function switch is in the I (Automatic) position and the rear wiper system control sleeve on the control stalk of the multi-function switch is in the I (Intermittent) position, the rear wiper operation will be synchronized with front wiper operation. The rear wipers will be automatically operated for one complete cycle each time the front wipers are cycled based upon the inputs from the rain/light sensor.

BACKUP WIPE MODE

When the transmission gear selector lever is placed in the REVERSE position with the front wiper system turned ON and the rear wiper system turned OFF, the rear washer pump is automatically activated for about 300 milliseconds (0.30 second) and the rear wipers are cycled 3 times. If the transmission gear selector lever is placed in the REVERSE position with the front wiper system and the rear wiper system turned ON, the rear wipers are cycled 3 times without activating the rear washer pump.

INTERMITTENT WIPE MODE

When the control sleeve on the control stalk of the multi-function switch is moved to the I (Intermittent) position, the SCM monitors this selection and sends an electronic rear wiper switch intermittent status message to the BCM. If the front wiper system is inactive, the BCM electronic intermittent wipe logic circuit responds by activating the rear wipers immediately for a single cycle, then activating the rear wipers for an additional cycle about every six seconds thereafter, until the front wipers are activated, or until the rear wiper system is turned OFF.

If both the front and rear wiper switches are in the I position, the rear wiper operation will be synchronized with front wiper operation and the rear wipers will be operated for one complete cycle each time the front wipers are cycled. On vehicles without the optional rain/light sensor, if the front wiper system is in one of the continuous operating modes and the rear wiper switch is in the I position, the rear wipers will be operated for one complete cycle for every 5 cycles of the front wipers. On vehicles with the optional rain/light sensor, if the front wiper system is in one of the continuous operating modes and the rear wiper switch is in the I position, the rear wipers will be operated for one complete cycle for every 10 cycles of the front wipers at vehicle speeds below about 80 kilometers-per-hour (50 miles-per-hour), and one complete cycle for every 7 cycles of the front wipers at vehicle speeds above about 80 kilometers-per-hour (50 miles-per-hour).

REAR DOOR AJAR MODE

If the rear wiper system is ON and either rear door is opened while the vehicle speed input is 0 kilometers-per-hour (0 miles-per-hour), both rear wiper motors are deactivated. If the rear doors are closed or if the vehicle speed input is greater than 0 kilometers-per-hour (0 miles-per-hour), both rear wiper motors are reactivated.

WASH MODE

When the sleeve on the control stalk of the multi-function switch is rotated to the momentary upward position from 0 (Off) or to the momentary downward position from I (Intermittent), the SCM monitors this selection and sends an electronic rear washer switch status message to the BCM. The BCM then activates the rear washer pump/motor unit for as long as the switch is held closed and operates the rear wipers. The rear wipers are cycled two times after the rear wash switch is released before returning to their previously selected 0 or I operating mode. The rear washer pump/motor unit can be operated for a maximum of about 15 continuous seconds per rear washer switch activation.