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)

Outside Rearview Mirror Operation

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

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 two built-in switches to the driver door module (DDM) and the passenger front door module (PDM), via the class 2 serial data circuit.

Battery voltage to the DDSA is supplied by the DRV MDL 10 amp fuse in the rear fuse block, through the driver door module (DDM). The DDSA is grounded, through the DDM, to a ground stake.

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, left or right, will be adjusted. One of the mirrors must be selected before the DDSA can send the Mirror Position Switch signals generated by the actual adjustment of the mirror selected to the appropriate front door module.

The Mirror Position Switch has 4 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 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. The DDSA then sends this information, via the class 2 serial data line, to the appropriate DDM or PDM. The DDM or PDM then moves the applicable mirror to the requested position.

On vehicles that have the A45 memory mirrors feature, the DDSA is also wired to, and receives direct signal inputs from, the memory function switch.

Mirror Motors

Each mirror has 2 reversible motors for position adjustment. These are the vertical motor and the horizontal motor. 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, 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 voltage and ground it supplies to these 2 circuits in order to move the motor in an opposite direction.

Memory Mirrors (A45) Personalization Option

The vehicle may be equipped with the A45 memory mirrors feature. However, the front door modules cannot perform memory mirror functions unless the Personalization Option is activated. The Dash Integration Module (DIM) stores the vehicles 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 mirror position sensors, 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 mirror position sensors provide the door modules with mirror position information. The door modules store the mirror position information and supply the voltage and ground neccessary to run the mirror motors.

When the vehicle operator programs a mirror position into the personalization package, the door modules store the position information and assign it a 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 mirrors vertical and horizontal position motors are equipped with a position sensor that provides constant information, in the form of feedback voltage to the associated door module indicating the vertical and horizontal position of the mirror. The mirror position sensors are potentiometers which are an internal part of each mirror motor. The front door modules each supply reference voltage through a separate 5 volt reference circuit, and ground through a separate mirror sensor low reference circuit to their respective mirror position sensors. When the mirror motors run, the resistance of the attached sensors vary, which in turn, varies the feedback voltage to the door module. Sensor feedback voltages vary between 0.25 volts and 4.75 volts.

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 mirror motor positions by storing the feedback voltage of their respective position sensors. When a memory Recall command is received, each door module moves the mirror 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 Inside Rearview 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 and each mirror contains an additional power folding mirror motor. 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 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 will cause them to unfold and vice-versa.