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 -- DDSA and DDM logic, DDM internal driver operation
    • PASS MDL 10A fuse -- PDM logic and internal driver operation

Outside Rearview Mirror Operation

The outside rearview mirrors are controlled by the driver door switch assembly (DDSA) which contains the mirror control switches, the driver door module (DDM), and the front passenger door module (PDM). The DDSA decodes mirror control switch activations while the door modules apply battery voltage and ground to their respective mirror motors to move the mirrors to the desired positions.

Door Modules Power and Ground

Each front door module has a separate battery voltage circuit fed by the rear fuse block. Each front door module is separately grounded through one or more circuits connected to a ground stake. These circuits are in the C3 harness connector of each front door module and are used for power outside rearview mirror operations, as well as to power up the modules. The driver door module (DDM) also uses these power and ground circuits to supply the driver door switch assembly (DDSA) with power and ground. In addition, the circuits are used for power door lock operations and for some power window functions, which are covered in the applicable power door locks or power windows description and operations sections.

The DDSA battery voltage circuit is fed, through the DDM, by the DRIVER DR MOD 10 amp fuse located in the left rear fuse block.

The DDM battery voltage circuit is fed by the DRIVER DR MOD 10 amp fuse located in the left rear fuse block.

The PDM battery voltage circuit is fed by the PSGR DR MOD 10 amp fuse located in the right rear fuse block.

These circuits must not be confused with the voltage and ground circuits of the door modules C1 harness connectors, which are used exclusively to drive the power window motors.

Outside Rearview Mirror Switches

For outside rearview mirror adjustments, the driver door switch assembly (DDSA) contains two built-in switches, the Mirror Select Switch and the Mirror Position Switch. The Mirror Select Switch is used to select which mirror, left or right, is to be adjusted. The Mirror Position Switch is used to move the mirror that has been selected for adjustment to the desired position. The DDSA reports the activity of these switches to the driver door module (DDM) and the front passenger door module (PDM) via the class 2 serial data circuit.

The Mirror Select Switch contacts, which are normally open, receive voltage and ground from the DDSA. When, either the left or right mirror has been selected for adjustment, the contacts indicating that selection are closed to ground and the voltage is pulled low. The DDSA processes this voltage information to determine which mirror will be adjusted.

The Mirror Position Switch has four sets of contacts, one set in each corner of the switch. The DDSA supplies voltage to one side of each set of contacts, and ground to the other side of each set of contacts. When the contacts close, voltage flows through them to ground and the DDSA interprets this as a specific mirror direction request signal. The DDSA then sends the request to the appropriate door module via the class 2 serial data circuit.

The Mirror Position Switch contacts are designated as Left-Up, Left-Down, Right-Up, and Right-Down. When the switch is activated in a Left-Up, Left-Down, Right-Up, or Right-Down direction, the switch closes the corresponding set of contacts, the DDSA interprets the signal and sends the information, via the class 2 serial data circuit, to the appropriate front door module, DDM or PDM. However, when the switch is activated in a direct Up, Down, Left, or Right direction, two sets of the contacts are closed. The DDSA recognizes the two contact signal as a one direction signal in the direction common to the two signals. For example, when the switch is activated to the Up direction, both the Left-Up and the Right-Up contacts are closed. The direction common to the two sets of contacts is Up. The DDSA interprets this signal as an Up command and sends the information, via the class 2 serial data circuit, to the appropriate front door module. Once the appropriate front door module receives the request, it moves the associated mirror to the requested position.

On vehicles that have the memory mirrors feature, the DDSA is also wired to, and receives direct signal inputs from, the memory function switch. For more information concerning the memory function switch refer to Memory Seats Description and Operation in Seats.

Mirror Motors

Each mirror has two reversible motors for position adjustment; the vertical motor and the horizontal motor. Each reversible mirror motor is wired to its associated door module through two motor control circuits. The door modules control the reversible motors by applying battery voltage and ground to these two motor control circuits. The door module reverses the polarity of the voltage and ground it applies to these two circuits in order to run the mirror motor in opposite directions. For example, to run the mirror in the Up direction, the door module applies voltage to the mirror motor up control circuit, and ground to the mirror motor down control circuit. To run the mirror in the opposite Down direction, the module reverses the polarity, supplying voltage to the down control circuit, and ground to the up control circuit.

When the mirror is operated in a Left-Up, Left-Down, Right-Up, or Right-Down direction, the associated door module applies voltage and ground to the appropriate control circuits of both the vertical motor, and the horizontal motor to move the mirror in both corresponding directions.

When the mirror is operated in a direct Up, Down, Left, or Right direction, the associated door module applies voltage and ground to only that motor which controls movements in the one corresponding direction. For example, if the switch is operated to a direct Up position, the associated door module applies voltage and ground only to the appropriate control circuits of its vertical motor.

Personalization -- Driver Information Center (DIC)

The vehicle may be equipped with the memory mirrors feature. However, Personalization in the Setup menu of the driver information center (DIC) must be in the active state for memory mirrors to operate. A check mark appearing after the word Personalization on the display screen indicates that the feature is active. For more detailed information concerning programming of personalization and other memory recall features controlled through the DIC, refer to Driver Personalization in Personalization.

Personalization Option -- Dash Integration Module (DIM)

Front door modules also cannot perform memory mirror functions unless the Personalization Option in the the dash integration module (DIM) is activated. The DIM stores the Personalization Option setting provided at the assembly plant and reports the 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 store the Personalization Option setting provided by the DIM 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 memory, the door modules will erroneously set DTCs B1586 and B1591.

Memory Mirrors Operation

The memory mirrors are controlled by the mirror position sensors, the driver door switch assembly (DDSA), and the front door modules. The DDSA decodes memory switch activations while the mirror position sensors provide mirror position information to the front door modules. The front door modules supply voltage and ground to the mirror position sensors, store mirror position information, and apply voltage and ground to run the mirror motors.

For memory operations, each outside rearview mirror has four additional circuits and contains a vertical position sensor and a horizontal position sensor. The position sensors, which are potentiometer type sensors, are attached to the corresponding position motor of each mirror, and provide constant information, in the form of feedback voltage to the associated door module to indicate the vertical and horizontal position of the mirror. Each position sensor of each mirror is wired to the corresponding front door module through four circuits to provide mirror location information in the following manner. Each front door module supplies 5 volts reference voltage through a 5 volt reference circuit, and ground through a mirror sensor low reference circuit, to both of its position sensors. Each front door module also supplies 5 volts through the vertical position sensor signal circuit, and, 5 volts through the horizontal position sensor signal circuit, to the corresponding position sensor. When the mirror motors run, the resistance of the attached sensors vary, which in turn, varies the feedback voltage to the door module. Feedback voltage for each sensor varies between 0.25 volts and 4.75 volts.

When mirror positions are programmed into the personalization package, the front door modules store the positions indicated by the feedback voltages of the position sensors. When a memory recall is requested, the door modules compare the feedback voltages indicated by the current mirror positions to the stored feedback voltages. The door modules then move the mirrors until the current feedback voltages match the stored feedback voltage levels.

Memory Mirrors -- Parallel Parking Mode

The vehicle is equipped with the parallel parking mode feature. For this feature, the front passenger door module (PDM) communicates with the powertrain control module (PCM) over the class 2 serial data circuit. When the gear selector is shifted to reverse, the PCM transmits this status via a class 2 message to the PDM. The PDM then applies voltage and ground to the vertical motor of the RH outside rearview mirror to tilt the mirror down 7 degrees. This allows the driver to see the curb while parallel parking. When the gear selector is shifted out of reverse, the PDM powers the vertical mirror motor to return the mirror to its previous position.

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 front passenger 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 applies battery voltage to the LH outside rearview mirror heating element via the feed circuit, and ground via the return circuit.

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

Power Folding Mirrors

Export vehicles may also have the power folding mirrors feature. The operator may simultaneously retract both mirrors to a fully folded position, in which they are closely tucked in and parallel to, the front door windows, or simultaneously extend both mirrors 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 and, each mirror contains an additional power folding mirror motor. When the switch is activated to fold the mirrors, the switch contacts close, the DDSA interprets the signal input, and sends the command on to the driver door module (DDM) and the front passenger door module (PDM). The DDM and the PDM then each apply battery 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 applied to the reversible folding motors in order to move both mirrors to the fully extended position.

The power folding mirrors switch is activated by momentarily pressing the switch button. 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 button will cause them to unfold and vice-versa.