Principles of Operation

PRINCIPLES OF OPERATION

The exterior mirrors are electrically controlled by the exterior mirror control switch for both vertical and horizontal movement. The exterior mirror control switch is hardwired to the driver door module (DDM). When the LH exterior mirror is selected, adjustment is carried out by moving the control switch to the desired position. The DDM receives the adjustment command from the exterior mirror control switch and supplies voltage and ground to the appropriate LH exterior mirror motor to adjust the LH exterior mirror. The RH exterior mirror is controlled by the front electronic module (FEM). When the DDM receives an adjustment command for the RH exterior mirror from the exterior mirror control switch, the DDM interprets the command and sends the adjustment command over the standard corporate protocol (SCP) communication network to the FEM. The FEM interprets the command and supplies voltage and ground to the appropriate RH exterior mirror motor to adjust the RH exterior mirror.

Memory (if equipped)
The memory mirror function recalls the preferred positioning of the exterior mirrors. Memory is activated by the door-mounted switches, the remote keyless entry (RKE) transmitter or the RKE keypad. The DDM and FEM constantly track the exterior mirror position using the potentiometers in the exterior mirror assembly. The positions remain in memory as long as the module retains power. When a memory position is recalled by the operator, the DDM and the FEM power the exterior mirror motors simultaneously and monitor the potentiometer circuits. When the stored memory position is reached, the DDM and FEM remove power from the motors. If the exterior mirror control switch is operated during a memory recall, the modules stop the recall and respond to the exterior mirror control switch command.

Heated Exterior Mirrors
The heated mirror function provides electric heating to both the LH and RH exterior mirrors, which raises the temperature of the glass to clear frost and condensation. The heated exterior mirrors are activated when the heated rear window is in operation, and automatically shut off after 15 minutes. The heated mirror power is supplied by the heated rear window relay through a separate battery junction box (BJB) fuse that isolates the heated mirrors from the heated rear window in the event of a concern with one of the systems.

Auto-Dimming Rear View Mirrors
This feature reduces glare caused by headlamps reflecting in the interior rear view mirror or LH exterior mirror. There are 2 integral sensors to control the dimming function. This feature is switched off by pressing the MODE switch on the interior rear view mirror to the OFF position. The auto-dimming interior rear view mirror defaults to the normal setting when the transmission is placed in REVERSE. The rear electronic module (REM) receives a reverse input from the PCM over the SCP communication link, then supplies a power signal to the interior mirror, causing the mirrors to cancel any dimming function. When the transmission is moved out of REVERSE, the auto-dimming mirrors return to normal operation and resume any interrupted dimming function.

If the REM does not receive the reverse input from the PCM, a communication diagnostic trouble code (DTC) is logged. As a default, the REM supplies power to the dimming circuit to prevent the automatic dimming function from operating until the communication is restored.

The transmission reverse information has a time delay before the message is sent by the PCM to the REM. This delay allows for the transmission selector to be moved through REVERSE without canceling the dimming operation.