GM Service Manual Online
For 1990-2009 cars only

Outside Mirror System Components

The power outside mirror system consists of the following components:

    • Driver door switch assembly (DDSA)
    • Driver door module (DDM)
    • Passenger door module (PDM)
    • Driver outside mirror
    • Passenger outside mirror
    • Power door serial data circuit
    • 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, two 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 reports the switch activity to the driver door module (DDM) via the power door serial data circuit.

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 to the desired position. When the mirror position switch is activated in a Up, Down, Left, or Right direction, the DDSA recognizes the input and sends this data on to the DDM. Depending on which mirror has been selected for adjustment, the DDM either moves the driver door mirror to the requested position, or sends a power door serial data message to the passenger door module (PDM) indicating that the passenger door mirror needs to be moved. The PDM then moves the passenger door mirror to the requested position.

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

LH Mirror

For a LH mirror left movement, the driver door module supplies battery positive voltage (B+) via the left mirror motor left circuit, and ground via the left mirror motor right circuit to the LH mirror horizontal motor. For a LH mirror right movement, the driver door module reverses the polarity and supplies battery positive voltage (B+) via the left mirror motor right circuit, and ground via the left mirror motor left circuit to the LH mirror horizontal motor. For a LH mirror up movement, the driver door module supplies battery positive voltage (B+) via the left mirror motor up circuit, and ground via the left mirror motor down circuit to the LH mirror vertical motor. For a LH mirror down movement, the driver door module reverses the polarity and supplies battery positive voltage (B+) via the left mirror motor down circuit, and ground via the left mirror motor up circuit to the LH mirror vertical motor.

RH Mirror

For a RH mirror left movement, the passenger door module supplies battery positive voltage (B+) via the right mirror motor left circuit, and ground via the right mirror motor right circuit to the RH mirror horizontal motor. For a RH mirror right movement, the passenger door module reverses the polarity and supplies battery positive voltage (B+) via the right mirror motor right circuit, and ground via the right mirror motor left circuit. For a RH mirror up movement, the passenger door module supplies battery positive voltage (B+) via the right mirror motor up circuit, and ground via the right mirror motor down circuit to the RH mirror vertical motor. For a RH mirror down movement, the passenger door module reverses the polarity and supplies battery positive voltage ( B+) via the right mirror motor down circuit and ground via the right mirror motor up circuit.

Memory Mirrors (W/A45)

The vehicle may be equipped with the "personalization package" containing memory seats and memory mirrors. The memory mirrors are controlled by the driver door switch assembly (DDSA) , the driver door module (DDM), and the passenger 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 two 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 memory seat/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 -- Parallel Parking Mode

If the vehicle is equipped with memory mirrors, it is equipped with the parallel parking mode feature. For this feature, the driver door module 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 driver door module. The driver door module sends this message on to the passenger door module over the power door serial data circuit. The passenger front door module (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 receives a class 2 message from the instrument panel cluster (IPC) via the rear integration module (RIM) commanding the heated mirrors ON. The DDM also examines information from the dash integration module (DIM) to determine if vehicle conditions are correct for the heated mirrors function to occur. If conditions are correct, the DDM then commands the driver side mirror heater ON, and sends a power door serial data message to the passenger front door module (PDM) to command 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.