The memory outside the rear view mirror is comprised of the following system components:

Each mirror is controlled by a pair of permanent magnet motors:

The vertical motor moves the mirror up and down. The horizontal motor moves the mirror left and right. The direction the motors turn depends on the supply voltage polarity sent to the motors. Each motor has an associated position sensor when the memory option is installed. These sensors are potentiometers which are linked to each motor. As the motor rotates, the potentiometer resistance is varied.

The LH Front Power Window Switch contains the mirror control switches:

The mirror selection (left or right) and the movement (up-down or left-right) is controlled by operating the mirror controls on the LH front power window switch. The motors are directly controlled by the door modules. The driver's door module (DDM) controls the driver's side outside power mirror. The passenger door module (PDM) controls the passenger's side outside power mirror. The LH front power window switch furnishes mirror switch positions to the DDM. The DDM decodes the switch information and directly controls the driver's mirror motors in order to move that mirror. If the DDM receives switch information in order to reposition the passenger's mirror, the DDM sends the information to the PDM. The PDM then drives the motors in order to reposition the mirror. Mirror X and Y position information is provided from the scan tool.

Each front door contains a door module. Both of the door modules contain logic in order to control the mirror motors and the memory in order to retain the mirror position information. The driver door module (DDM) also contains circuitry in order to communicate over the class 2 bus. The mirror positions are determined by the voltage levels sent to the respective door module by the position sensors. The door modules monitor the voltage drop across these sensors and store those values in memory, whenever a memory switch is held to the set position. The values are called from memory and are used in order to reposition the mirrors when a memory recall is selected.

There are 2 simple bus interface (SBI) segments. One segment is used in order to transmit messages containing switch information between the power door lock switch and the driver's door module (DDM). A second SBI segment is used for serial communications between the DDM, the PDM, and the RDM. The PDM does not communicate directly with the driver's door switch.

The class 2 bus is a vehicle-wide communications link. This class 2 link is mandated by the federal government for use on on-board-power mirror diagnostics (OBD) of the powertrain control module (PCM). The use of this bus has been expanded to include most of the modules on this vehicle. The mirror system utilizes the class 2 bus for messages between the remote function actuator (RFA) and the driver door module (DDM). A class 2 bus message is also used in order to relay the transmission gear position for memory recall use. The RFA is the receiving device for the keyless entry. The RFA keyless entry transmitters broadcast codes in order to identify which keyless entry transmitter, or driver, has unlocked the vehicle. The driver identity message is sent over the class 2 bus to the DDM, and the other modules, in order to reposition all of the personalized vehicle features for that driver.

Operation of the memory mirrors is similar to that of the memory seats. There are 2 modes of control:

Memory recall can be done either through a keyless entry transmitter or by momentarily depressing one of the driver's door memory switches:

The door modules will automatically drive the mirrors to the position stored in memory whenever a mirror memory switch is pressed momentarily (recall).

The door modules will automatically drive the mirrors to the position stored in memory whenever a keyless entry transmitter is operated in order to unlock the vehicle. The keyless entry transmitters have individual transmission codes in order to identify the driver.

The mirror motor position sensors are used in order to remember the mirror positions. These sensors are potentiometers contained in the mirror's drive unit. As the mirror motors turn, the potentiometer resistance is varied. The mirror position is determined by the sensor voltage level for the existing mirror position seen by the associated door module. If one of the memory buttons is pushed and held for at least 3 seconds, the sensor voltage level is stored in order to remember the mirror positions for that switch (DRIVER 1/2).

The mirror heat function is linked to the rear window defogger. When the rear defogger is active, a class 2 bus message is sent from the heating, ventilation and air conditioning (HVAC) control module (HCM) to the driver door module (DDM). The DDM activates the driver's side outside rear view mirror heating element in order to clear the mirror of mist or frost. The DDM sends a simple bus interface (SBI) message to the passenger door module (PDM) in order to heat the passenger side outside rear view mirror. The mirror heating element will not de-ice a mirror except at temperatures just below freezing. The mirror heat status is provided from the scan tool.