Principles of Operation

Glass, Frames and Mechanisms

Principles of Operation

Delayed Accessory Power

The Body Control Module (BCM) controls voltage to the power windows with the accessory delay relay. The BCM (Body Control Module) activates the accessory delay relay whenever the ignition is in the RUN or the ACC position, or when the ignition is changed from RUN or ACC to the OFF position and the LH and RH front doors are closed.

The BCM (Body Control Module) deactivates the accessory delay relay when:

- the LH front door is ajar and the ignition is in the OFF or key-out position.

- the RH front door is ajar and the ignition is in the OFF or key-out position.

- ten minutes have elapsed since the ignition was changed from ACC or RUN to the OFF position.

LH and RH Front Power Window Control

The LH and RH front door window motors have integral electronics and must be initialized whenever a new window motor has been installed. Initialization is required to learn the full UP position and the profile of the glass as it travels through the glass channel. Once initialized, obstacle detection is enabled. When mechanical repairs have been carried out on the window regulator or glass run, the window motor must be de-initialized, and then initialized. The window control switch sends 2 separate signals to the window motor: up and down. When the window control switch is pressed to the first detent position, a 12-volt signal is sent to the window motor to request an up or down operation. When auto up or auto down is requested (switch pressed to the second detent position), the window control switch provides a 12-volt signal on both the up and down line simultaneously. During an auto up or auto down request, the window motor determines intended window direction by the signal first received. If the window control switch is pressed too quickly to the second detent position (less than 5 milliseconds of time between first detent signal and second detent signal), the window motor is not able to determine the intended direction request and cannot operate until the window control switch is released and pressed again. The up and down contacts are floating within the window control switch when the switch is in the neutral position. The up and down feeds to the window motor are all low current.

The LH and RH front window motors operate when the delayed accessory relay is active. The high current required to move the front windows are supplied through the B+ and motor ground input.

The LH and RH front window regulator motors have a protection shutdown feature that disables the motor operation if the windows are continually operated up and down for a number of cycles (6-10). The feature disables the motor operation for 5 minutes to prevent damage to the regulator motors. Normal operation will resume when the window switch has been inactive for 5 minutes.

When the LH or RH front window motor is operating in auto up or auto down mode, movement of the front window can be stopped by pressing the switch to any position (UP, DOWN, auto UP, auto DOWN). The front window control switches must be released before the window can move again.

A new LH or RH front window motor cannot operate in one-touch up mode and the bounce-back feature is disabled prior to initialization. If the switch is actuated to the auto UP position and released, window movement stops when the up contact in the front window control switch is released. If the front window motor is removed from the window regulator drum housing, or if a new front window motor is installed, it must be initialized. Refer to Window Motor Initialization .

The front window motors automatically adjust to system changes throughout its life: changes in seal drag and slight changes in the full OPEN position occur and are automatically compensated for. Once initialized, the window motor soft stalls into the upper position contributing to extended durability of the system. If the window does not seal completely in the full UP position (very small gaps/non bounce-back events only), the window switch can be actuated to the UP position to energize the window motor for a fraction of a second to fully seal and this new position is learned.

Bounce-Back

The front window motors have a bounce-back feature. If an obstacle has been detected in the window opening as the window glass is moving upward, the window motor automatically reverses direction and moves the glass toward the bounce-back position (in both up and one-touch up modes). If an obstruction occurs between 4 mm (0.15 in) and 200 mm (7.87 in) of window opening, the bounce-back position is approximately at 250 mm (9.84 in) of window opening. If an obstruction occurs at a position greater than 200 mm (7.87 in) of window opening, the bounce-back position is approximately at 50 mm (1.96 in) below where the obstruction occurred.

Security Override

To override a bounce-back condition (to overcome the resistance of ice on the window or seals for example), within 2 seconds after the window reaches the bounce-back position, pull and hold the window control switch. The window travels up with no bounce-back or pinch protection. If the window control switch is released before the window is fully closed, the window stops. If the ignition is turned to OFF or START (without delayed accessory), the window motor stops.

Rear Passenger Window Operation - SuperCab and SuperCrew Only

Rear passenger windows can be raised or lowered using the LH front window control switch or the corresponding passenger window control switch. The rear passenger window control switches receive power when the delayed accessory relay is active and the LH front window lock-out switch is in the UNLOCK position. When the LH front window lock-out switch is in the LOCK position, the rear passenger windows only operate from the LH front window control switch.

Rear Window Defrost (if equipped)

When the rear window defrost switch (integral to the HVAC module or Front Controls Interface Module (FCIM) if equipped with navigation system) is pressed and the engine is running, the HVAC module activates the rear window defrost relay located in the Battery Junction Box (BJB). When the rear window defrost relay is active, the rear window defrost grid is energized and the rear window defrost status LED is illuminated. For vehicles equipped with a power sliding rear window, the rear window defrost grid does not activate unless the rear sliding window glass is in the fully CLOSED position due to a glass position switch in series with the grid circuit. The glass position switch is integral to the power sliding rear window assembly. There is a feedback circuit incorporated into the glass position switch which illuminates the rear window defrost switch LED when the defrost grid is active and the sliding glass is fully closed. If the sliding glass is opened while the defrost system is active, the heated mirrors continue to operate and the rear window defrost switch LED is no longer illuminated.

The HVAC module deactivates the rear window defrost relay when one of the following conditions is met:

- The rear window defrost switch is pressed when the feature is active

- Ignition state is changed from RUN to OFF/LOCK

- The 15-minute timing function is completed

Feature Inputs

- Ignition RUN position (12V on both RUN and RUN/ACC inputs)

- Rear window defrost switch (momentary contact to ground when switch is pressed)

Feature Output

- Rear window defrost relay control (grounded when activated, open circuit when deactivated)

Remote Start Climate Operation (if equipped)

The customer can select different climate control modes/preferences when the vehicle is started using the remote start feature. This can be accessed through the message center. For information on how to set the remote start preferences, refer to the Owner's Literature. When the rear defrost is set to AUTO mode, the rear window defrost activates when the outside temperature is less than 0° C (32° F) and the vehicle is started using the remote start feature. No climate control adjustments are recognized during remote start operation. Once the ignition is cycled to the ON position, the climate control system returns to the previous settings (last ignition-ON cycle) and adjustments can be made normally. If the previous setting was off, the climate control system turns off.