GM Service Manual Online
For 1990-2009 cars only

Outside Mirror System Components

The power outside rearview mirror system consists of the following components:

    • Driver door switch assembly (DDSA)
    • Driver door module (DDM)
    • Passenger front door module (PDM)
    • Driver outside mirror
    • Passenger outside mirror
    • Class 2 serial data link
    • DRV MDL 10A fuse -- door module logic and internal driver operation
    • PASS MDL 10A fuse -- door module logic and internal driver operation

Driver and Passenger Outside Mirror Operation

In order to control outside rear view mirror adjustments, 2 switches are contained within the driver door switch assembly (DDSA). The DDSA contains a built in mirror select switch, and a built in mirror position switch. The DDSA is also wired to, and receives direct signal inputs, from the memory function switch. For power mirror operations, the DDSA reports the switch activity to the driver door module (DDM) and the passenger front door module (PDM).

The mirror select switch is used to select which mirror, left or right, is to be moved.

The mirror position switch is used to move the mirror that has been selected for adjustment to the desired position. There are 4 contacts located in the switch, one in each corner. The contacts are designated as Left-Up, Left-Down, Right-Up, and Right-Down. When the switch is activated in a direct Up, Down, Left, or Right direction, the switch hits 2 of the contacts. The DDSA recognizes the 2 contact signal as a 1 direction signal in the direction common to the 2 signals. Depending on which mirror has been selected for adjustment, the DDSA then sends this information, via the class 2 serial data line, to the DDM or the PDM. The DDM or PDM then moves the applicable mirror to the requested position.

Mirror Motors

Each mirror has 2 reversible motors for position adjustment. The door modules control the reversible motors by supplying Battery Positive Voltage (B+) and ground to these motors.

When the mirror position switch has been activated in a direction that closes only 1 set of its contacts, the associated door module supplies battery positive voltage and ground to the appropriate circuits of both the vertical motor, and the horizontal motor to move the mirror in the 2 corresponding directions at the same time, i.e. Left-Up, Left-Down, Right-Up, or Right-Down.

When the mirror position switch has been activated in a direction that closes 2 sets of contacts, the associated door module supplies battery positive voltage and ground to only that motor which controls movements in the direction common to both contacts. For example, if the switch is activated to a direct Up position, both the Left-Up and the Right-Up contacts are closed. The direction common to the contacts is the Up direction. Since the DDSA interprets that as a 1 direction signal, the associated door module supplies battery voltage and ground only to its vertical motor to move the mirror UP.

Each reversible mirror motor is wired to its associated door module through 2 motor drive circuits. The door module reverses the polarity of the battery positive voltage and ground it supplies to these 2 circuits in order to move the motor in opposite directions.

Memory Mirrors (A45) Personalization Option

The front door modules cannot perform memory mirror functions unless the Personalization Option is activated. The Dash Integration Module (DIM) stores the Personalization Option setting provided at the assembly plant. The DIM reports this Personalization Option setting to both front door modules, as well as other receiving modules, each time the ignition switch is cycled to RUN. The front door modules then store the Personalization Option setting and examine it before making a memory mirrors adjustment.

The Personalization Option setting stored within the front door modules will not change until the Personalization Option setting within the DIM is changed and the ignition switch then cycled to RUN.

If the Personalization Option is activated on a vehicle that is not equipped with A45, the door modules will erroneously set DTCs B1586 and B1591.

Memory Mirrors (A45) Operation

The memory mirrors are controlled by the driver door switch assembly (DDSA), the driver door module (DDM), and the passenger front door module (PDM). The DDSA is used in decoding memory switch activations and the door modules are used to store mirror position information and move the mirrors.

When a mirror position is programmed into the personalization package, the door modules store the position information and assign it to the personalization code. During a memory recall, that personalization code is retrieved by the modules. The modules then check the current position of the mirrors and move them to the position matching the retrieved code.

Each mirror is equipped with 2 potentiometer type position sensors and circuits that provide constant information, in the form of feedback voltage to each door module indicating the position of the mirrors on their horizontal and vertical axis. The mirror position sensors are attached to each mirror motor's transmission cable. When the cable rotates, the resistance of the sensors vary and the feedback voltage is monitored by the appropriate door module to determine the mirrors position. The sensor feedback voltage varies from 0.25 volts to 4.75 volts. Each door module also supplies reference voltage through a 5 volt reference circuit, and ground through a mirror sensor low reference circuit to their respective mirror position sensors.

The driver door module receives feedback voltage from the LH mirror horizontal position sensor through the left mirror horizontal position sensor signal circuit and feedback voltage from the LH mirror vertical position sensor through the left mirror vertical position sensor signal circuit.

The passenger door module receives feedback voltage from the RH mirror horizontal position sensor through the right mirror horizontal position sensor signal circuit and feedback voltage from the RH mirror vertical position sensor through the right mirror vertical position sensor signal circuit.

When a memory Set command is received, each door module records the motor positions by storing the feedback voltage of their respective position sensors. When a memory Recall command is received, each door module moves the motors until the position sensor feedback voltages equal the feedback voltages stored in memory.

Memory Mirrors (A45) Parallel Parking Mode

The vehicle is equipped with the parallel parking mode feature. For this feature, the passenger front door module (PDM) communicates with the powertrain control module (PCM) over the class 2 data link. When the gear selector is shifted to reverse, the PCM transmits this status via a class 2 message to the PDM. The PDM then supplies battery positive voltage and ground to the vertical motor of the RH outside rear view mirror to tilt the mirror down 7 degrees. This allows the driver to see the curb while parallel parking.

Heated Mirrors

The mirrors heat during the defrost/defog cycles for the rear window. The heated mirrors are connected to the driver door module (DDM) and the passenger front door module (PDM). The DDM and the PDM receive a class 2 message from the instrument panel cluster (IPC) via the rear integration module (RIM) commanding the heated mirrors ON. The DDM and PDM first examine information from the dash integration module (DIM) to determine if vehicle conditions are correct for the heated mirrors function to be permitted. If conditions are correct, the DDM then commands the driver side mirror heater ON, and the PDM commands the passenger side mirror heater ON.

The DDM supplies battery positive voltage to the LH outside rearview mirror heating element via the feed circuit, and ground via the return circuit.

The PDM supplies battery positive voltage to the RH outside rearview mirror heating element via the feed circuit, and ground via the return circuit.

Automatic Day/Night Feature Operation

The automatic day/night feature of the driver outside rearview mirror is controlled by the inside rearview mirror. The inside rearview mirror supplies a signal and a low reference to the driver outside rearview mirror. The voltage on the signal circuit of the driver outside rearview mirror varies between 0.5 to 1.5 volts depending on light conditions present at the inside rearview mirror. At night, with the automatic day-night feature enabled, the driver outside rearview mirror will automatically darken with the inside rearview mirror to reduce the glare from the headlamps from behind. The voltage on the signal circuit of the driver outside rearview mirror will be near 1.5 volts. In the daytime, the mirrors are in a normal state. The voltage on the signal circuit of the driver outside rearview mirror may be less than or near 0.5 volts. Refer to Automatic Day-Night Mirror Description and Operation in Stationary Windows for further description and operation of the inside rearview mirror.

Power Folding Mirrors

Export vehicles may also have the power folding mirrors feature. This feature allows the operator to retract the mirrors to a fully folded position in which they are closely tucked in, and parallel to, the front door windows, or to extend them to the fully unfolded position for normal everyday use.

For this feature, the driver door switch assembly (DDSA) has an additional power folding mirrors switch built into it. When the switch is activated to fold the mirrors, the DDSA interprets the signal input and sends the command on to the driver door module (DDM) and the passenger front door module (PDM) The DDM and the PDM then each supply battery positive voltage and ground to the appropriate circuits of their respective power folding motors in order to retract both mirrors. When the switch is activated to unfold the mirrors, the door modules reverse the polarity of the voltage and ground supplied to the reversible motors in order to move both mirrors to the fully extended position.

The power folding mirrors switch is activated by momentarily pressing it and each subsequent press will activate the mirrors to the opposite function of the preceding press, i.e. if the mirrors are currently folded, the next press of the switch will cause them to unfold and vice-versa.