Principles of Operation (How Does It Work?)
PRINCIPLES OF OPERATIONFeatures and Operation
The generic electronic module (GEM) controls the opening of the LH driver side power window (window down motion) by activating the one-touch down (OTD) window relay. The one-touch down feature is a GEM only function.
- The driver side window has two downward motions: manual mode and auto mode. The down window mode is selected by pressing the driver window control switch (driver control). When the GEM detects that the driver window control switch has been pressed for a time greater than 0.4 second, it enters the manual mode. If the GEM detects that the driver window control switch was depressed between 0.04 and 0.4 second, it enters the auto mode. (The ignition switch is in the RUN or ACC position).
Auto Mode
Auto mode will be terminated when any of the following conditions are met:
- The LH window control switch is pushed to the up position or down position.
- Seven seconds have elapsed since auto mode was initiated.
- A window regulator motor stall condition is detected on the OTD sense line inputs.
One-Touch Down Relay
The GEM controls manual down and OTD window movement with the OTD relay for the LF window only.
The relay is activated by applying ground directly to one side of the down window relay coil, and is deactivated by removing the ground signal.
Power Rear Window
NOTE: The power rear window motor is not on the multiplex link. Any diagnosis and testing carried out on the power rear window will not involve the GEM module.
The power rear window motor is a 8-pin motor with integral electronics. The power rear window control switch is located on the instrument panel adjacent to the radio and provides a ground signal to the motor to signal an open, close or vent request. The integral electronics on the motor allow the power rear window to be moved to three positions: fully open, fully closed and vent (approximately two inches down from fully closed). The control switch is rotated clockwise and released to fully close the window, rotated counterclockwise and released to fully open the window, and pushed and released to actuate the window to the vent position.
The power rear window motor plastic pinion gear is mated to the drum housing of a single rail drum and cable window regulator. The motor is attached to the plastic drum housing by three screws. The motor uses internal Hall effect sensor feedback coupled to the microprocessor to determine window position and operate the power rear window. If the microprocessor is not receiving the Hall effect sensor pulses, the motor will run for approximately half a second, then enter error mode (window will become inoperative). The motor contains a thermal breaker to protect the motor windings from over-current/over-temperature operation. Continued successive operation of the motor will cause the thermal breaker to open, causing a loss of power until the power rear window motor cools.
The power rear window motor operates with the ignition switch in the RUN/ACC position only and is sensed by the RUN/ACC and logic ground inputs. The motor is supplied with battery power and draws a key off load of approximately 1 mA. All of the high current required to move the window is supplied through the battery and motor ground inputs. The loss of either logic or motor ground will cause this system to become inoperative. For correct functionality, both power feeds and both ground feeds must be intact at the power rear window motor.
If a down or vent command is selected while the ignition switch is in the RUN/ACC position, and the ignition switch is turned to OFF or START, the window will move to the fully open or vent position and stop. If an up command is selected while the ignition switch is in the RUN/ACC position, and the ignition switch is turned to OFF or START, the window will stop if it is between vent and fully closed, or will move to the vent position and stop if it is between vent and fully open.
If an obstacle is detected in the power rear window opening as the window is closing upward, the window will automatically reverse direction and move toward the fully open position. This is known as "bounce-back". If, during a bounce-back condition the window stops, and the power rear window control switch is released, then held in the up direction for at least two seconds, the window will travel up with no bounce-back protection (security override). If the ignition switch is turned to OFF or START, the window will reverse direction with bounce-back re-enabled. Ice, contaminant buildup, and environmentally induced tight spots in the window seals are all possible uses for the security override feature.
If power (B+) is disconnected from the power rear window motor while the window is in motion, the motor will enter position recovery mode when power is restored. Position recovery mode allows up and down movement of window in 15 mm (0.6 in) increments until the motor stalls the window glass in the upper header seal. If no internal or external faults exist, the motor will automatically resume normal operation.
The power rear window control switch is supplied with illumination and illumination ground inputs used to illuminate the control switch when the headlamp switch is turned to the PARK or ON position. These switch inputs do not affect operation of the window. The control switch uses the main ground input which is transferred to the open, closed, or vent outputs by closing a switch contact. If the main ground signal is missing, the window will become inoperative.
If the power rear window control switch, or its associated wiring, develops an open circuit, that function will become inoperative. If the open contact or associated wiring develops an open circuit, the window will only travel to the vent or fully closed positions. If the close contact or associated wiring develops an open circuit, the window will only travel to the fully open or vent positions. If the vent contact or associated wiring develops an open circuit, the window will only travel to the fully open or closed positions.
The power rear window motor will suspend normal operation if a power rear window control switch error exists. A control switch error is defined as open and close, open and vent, close and vent, or open, close and vent energized at the same time. The window will be inoperative if a control switch error is present.
If the motor is removed from the window regulator drum housing, or if a new motor is installed, the window must be initialized. A new motor will be in error mode and inoperative until initialized. Refer to Rear Window Motor Initialization. For positioning the window regulator for glass removal/installation, refer to Rear Window Positioning.
The power rear window will automatically adjust to system changes throughout its life. Changes in seal drag and slight changes in the fully closed position will occur and are automatically compensated for. Once initialized, the motor will soft stall into the upper and lower positions, contributing to the extended durability of the system.