GM Service Manual Online
For 1990-2009 cars only

Outside Mirror System Components

The power outside mirror system consists of the following components:

    • The driver door switch assembly (DDSA)
    • The driver door module (DDM)
    • The front passenger door module (PDM)
    • The LH outside rearview mirror
    • The RH outside rearview mirror
    • The DRV MDL 10-amp fuse
    • The Pass MDL 10-amp fuse
    • The power door serial data circuit
    • The class 2 serial data circuit

Power Outside Rearview Mirrors Operation

The power outside rearview mirrors are controlled by the driver door module (DDM), the front passenger door module (PDM), and the mirror control switches built into the driver door switch assembly (DDSA). The DDSA decodes mirror control switch activations and sends the information to the DDM via the power door serial data circuit. The DDM either applies voltage and ground to move the driver side mirror, or sends the information through the power door serial data circuit to the PDM, which applies voltage and ground to move the passenger side mirror.

Door Modules Power and Ground

In order to control power outside rearview mirror operations, as well as other door functions, the front door modules and the driver door switch assembly (DDSA) must be powered up. Instrument panel (I/P) and rear fuse blocks supply battery voltage, through separate circuits, to the driver door module (DDM) and passenger door module (PDM). Each front door module is separately grounded through a ground circuit and ground stake.

The DRV MDL 10-amp fuse located in the rear fuse block feeds the DDM battery positive voltage circuit.

The PDM 10-amp fuse located in the I/P fuse block feeds the PDM battery positive voltage circuit.

The DDM and PDM also use these voltage and ground circuits to provide power and ground to the circuits of the mirror position sensors and motors.

The DRV MDL 10-amp fuse located in the rear fuse block also feeds the DDSA battery positive voltage circuit, which is routed through the DDM. The DDSA is grounded, also through the DDM, to a ground stake. In addition to power up, the DDSA uses these voltage and ground supplies to provide voltage and ground to the integrated mirror control switches. The voltage and ground circuits of the front door modules are in the C1 harness connector of each module and must not be confused with the voltage and ground circuits of the C2 connectors, which are used exclusively for power window motor operation.

The DDSA has one discrete connector containing all of its circuits.

Power Outside Rearview Mirror Switches

For outside rearview mirror adjustments, the driver door switch assembly (DDSA) contains 2 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 actual movement of the mirror is accomplished using the mirror position switch. The DDSA reports the activity of these 2 built-in switches to the driver door module (DDM) via the power door serial data circuit. If the front passenger door mirror has been selected for adjustment, the DDM sends the information to the passenger door module (PDM) via the power door serial data circuit.

Battery voltage to the DDSA is supplied by the DRV MDL 10-amp fuse in the rear fuse block, through the 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 detects this voltage flow as an input signal and uses the information to determine which mirror will be adjusted.

The mirror position switch has 4 sets of contacts, one each for the up, down, left, and right directions. 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 DDM via the power door serial data circuit.

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

Mirror Motors

Each mirror has 2 reversible mirror motors for position adjustment, the vertical position motor, and the horizontal position motor. These position motors are built into the mirror and are not serviced separately. Each motor is wired to its associated door module through 2 motor control circuits. The door modules control the direction in which the mirror moves by applying battery voltage and ground, through these motor control circuits, to the 2 motors.

The direction in which the mirror moves depends on which motor control circuit the battery voltage is applied to, and which motor control circuit the ground is applied to. For an up movement, the door module applies battery voltage to the up control circuit, and ground to the down control circuit of the vertical position motor. The vertical position motor runs to move the mirror up. For a down movement, the door module reverses the polarity, applying battery voltage to the down control circuit and ground to the up control circuit of the vertical position motor. The motor runs to move the mirror down. Horizontal movements of the mirror are controlled the same way. For a left movement, the door module applies battery voltage to the left control circuit, and ground to the right control circuit. For a right movement, the door module reverses the polarity, applying battery voltage to the right control circuit and ground to the left control circuit.

Memory Mirrors (A45) 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 interpret and store mirror position information from the sensors, and supply the voltage and ground to run the mirror motors.

For memory operations, each outside rearview mirror has 4 additional circuits and contains a vertical position sensor and a horizontal position sensor. The position sensors are attached to the corresponding vertical and horizontal position motor of each mirror. The position sensors, which are potentiometer type sensors, provide constant information, in the form of feedback voltage, to the associated door module, indicating the vertical and horizontal position of the mirror. 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 the 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. The door module interprets and stores the feedback voltage of each sensor, which typically varies between 0.25-4.75 volts. The mirror position sensors are not serviced separately from the mirror.

When a mirror location is programmed into the personalization package, the front door modules store the mirror locations 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.

Auto-Tilt Parking Aid (W/A45)

If the vehicle is equipped with memory mirrors, the vehicle is also equipped with the park aid mirror system as a personalization option. This feature assists in parallel parking situations. The park aid mirror option is turned ON and OFF through the driver information center. The feature must be turned ON for the current memory setting in order to operate.

If the option is turned ON for the current or last driver identified, by either using the key fob transmitter or by pressing the driver memory switch on the door, the passenger side exterior mirror functions as listed:

    • The passenger side mirror will tilt down when the transmission is shifted into REVERSE.
    • The passenger mirror will return to the previous position when the transmission is shifted out of REVERSE.

The tilt mirror function will operate even if the mirror was positioned by using the mirror position switches, as long as the function is turned ON for the last driver identified.

In this system, the instrument panel cluster (IPC) sends a class 2 message to the driver door module (DDM) indicating the Reverse position of the transmission selector. The DDM sends a power door serial data message to the passenger door module (PDM), which powers the vertical mirror motor to tilt the passenger mirror down.

When the IPC detects the transmission is no longer in Reverse, the IPC sends the message to the DDM. The DDM sends a message to the PDM and the PDM powers the circuits to return the mirror to the original position.

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 0.5-1.5 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.

Heated Mirrors

The mirrors heat during the defrost/defog cycles for the rear window. The heated mirrors circuits are connected to the driver door module (DDM) and the passenger door module (PDM). When the standard body control module (BCM) receives the class 2 message from the instrument panel cluster (IPC) that the rear window defrost has been turned ON, it sends the message on to the DDM. When the DDM receives the class 2 message from the BCM commanding the heated mirrors ON, it supplies the voltage and ground to the appropriate circuits of the heater element built into the driver outside mirror and sends a power door serial data message to the PDM to command the passenger side mirror heater ON. The PDM supplies voltage and ground to the appropriate circuits of the heater element built into the passenger outside mirror.