Chevrolet Silverado / GMC Sierra. Service manual — part 2668

Right Outside Power Mirror-Contains both the vertical and horizontal mirror motors

Body Control Module-An electronic control module that requires programming when
replaced, serves as the power mode master and is the main message handler

Memory Switch, if equipped with memory mirrors-Supplied power by the DDS and
provides a voltage signal to the DDS upon a switch activation

Horizontal and Vertical Position Sensors, if equipped with memory mirrors-Supplied a 5-
volt and low reference by the DDS/PDS and provide a variable voltage signal to the
DDS/PDS that is proportional to mirror position

Powertrain Control Module (PCM), if equipped with memory mirrors-An electronic control
module that requires programming when replaced and provides the message indicating
transmission gear selection

Driver Information Center (DIC), if equipped with memory mirrors-Part of the instrument
cluster which is a an electronic control module that requires programming when replaced
and is used to personalize the memory recall functions

Fold Motor, in each of the outside mirrors, if equipped with power fold mirrors-Provides
extend and retract movements of the mirror and is serviced as a complete mirror assembly

Each of the outside power mirrors contains 2 reversible motors to provide horizontal and vertical
movement of the mirror glass. The vertical motor operates the up and down directions and the
horizontal motor operates the left and right directions. If equipped with power folding mirrors,
each outside power mirror will contain a reversible fold motor to operate the extend and retract
functions. Each of the mirror motors are circuit breaker protected.

Power Mirror System Controls

The power mirror switch incorporates a 3-position mirror select switch and a 4-position mirror
direction switch. The mirror select switch allows the operator to select the mirror to be moved by
selecting the L position for the left power mirror, selecting the R position for the right power
mirror or the center which is the neutral/fold position. The mirror direction switch is a 4-position
switch that allows the operator to move the selected mirror up, down, left or right. The mirror
direction switch also functions as the folding mirror switch. When the selector switch is in the
neutral/fold position, activate the mirror direction switch to the left to extend the mirrors and
right to retract the mirrors.

Power Mirror System Operation

The power mirror switch is integrated into the DDS. The left and right mirror positions of the
select switch and 4 positions of the direction switch, when active, will provide a signal to the
DDS. If the selector switch is placed in the L position and the up switch is depressed, 2 signals

2008 Chevrolet Silverado 1500

2008 ACCESSORIES & EQUIPMENT Mirrors - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado

will be supplied to the DDS. The DDS upon receipt of these signals will provide battery voltage
to the mirror motor left/up control circuit and ground to the mirror motor down control circuit
and the mirror will move up. The remainder of the driver mirror functions operate in the same
manner as described above except the DDS will supply battery voltage and ground to the
appropriate control circuits for the direction selected. If the passenger mirror is selected and a
direction switch is activated, the DDS sends a LAN message to the PDS indicating that the
passenger mirror was selected and the direction to be commanded. The PDS will then supply
battery voltage and ground to the appropriate control circuits for the direction selected.

Memory Mirror System

Memory Mirror System Controls

The driver door switch (DDS) and passenger door switch (PDS) are capable of storing mirror
positions and controlling the mirrors to these positions to the preferred settings of 2 different
drivers. Each driver will be able to personalize the memory system by positioning the mirrors and
seats to their preferred settings. Then press and hold the memory 1 or memory 2 button until an
audible chime is heard and the current mirror positions will be stored into memory of the DDS
and PDS. Seat position will be stored in the driver position module (DPM). Once the mirror and
seat positions have been stored into memory, a momentary memory 1 or memory 2 switch
activation will supply the DDS a battery voltage signal. The DDS, upon receipt of the memory
switch signal, with the transmission in park or neutral, will then drive the driver mirror to the
corresponding stored memory position. The DDS will also send a LAN message to the PDS and
DSM indicating that a memory switch activation occurred. The PDS will then drive the passenger
mirror and the DPM will drive the driver seat to the corresponding stored memory position. The
memory system can also be controlled by any of the following if programmed using the driver
information center (DIC) to enable/disable the features:

Auto exit/entry seat positioning

Mirror and seat position recall on a keyless entry unlock activation

Mirror and seat position recall on ignition key insertion

For further information on programming and configuration, refer to Driver Personalization in
Personalization.

Memory Mirror System Operation

Mirror position is determined by both horizontal and vertical position sensors in each of the
power mirrors. The DDS and PDS supplies a reference voltage and a low reference to these
sensors and determines mirror position through the horizontal and vertical position signal circuits.

2008 Chevrolet Silverado 1500

2008 ACCESSORIES & EQUIPMENT Mirrors - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado

The memory switch receives power from the DDS through the battery supply voltage circuit and
the DDS fuse. The DDS upon receipt of a memory switch signal input or an appropriate LAN
message from the BCM, the DDS and PDS will then supply battery voltage and ground to the
appropriate power mirror motors through the mirror motor control circuits to move the mirrors to
the predetermined positions.

Folding Mirror System

Folding Mirror System Controls

The folding mirror system requires signals from 2 separate switches. The mirror select switch
must be in the neutral/fold position and the mirror direction switch must be activated to the
left/extend or right/retract positions. Both switches are integrated into the DDS and provide
direct signals.

Folding Mirror System Operation

Upon receipt of the required switch inputs the DDS will supply battery voltage and ground to the
mirror fold motor control circuits to perform the requested extend or retract function. The DDS
will also send a LAN message to the PDS indicating the requested function. The PDS will supply
battery voltage and ground to the mirror fold motor control circuits to perform the requested
extend or retract function.

AUTOMATIC DAY-NIGHT MIRROR DESCRIPTION AND OPERATION

Inside Rearview Mirror with the Automatic Day-Night Feature System Components

The inside rearview mirror with the automatic day-night feature system consists of the following
components:

Inside rearview mirror

Ambient air temperature sensor

Inside Rearview Mirror with the Automatic Day-Night Feature System Operation

The inside rearview mirror uses 2 photocell sensors. One sensor is the headlight sensor, located
on the face side of the mirror. The headlight sensor is used to determine light conditions present at
the mirror face. The other sensor is the ambient light sensor, located on the rear of the mirror or
windshield side. The ambient light sensor is used to determine the exterior light conditions. With
a low exterior light condition detected, and a high light condition from behind of the car, at the
headlight sensor, the inside rearview mirror will automatically darken the face of the mirror.

In the daytime, the mirror is in a normal state because of the high exterior light condition that is

2008 Chevrolet Silverado 1500

2008 ACCESSORIES & EQUIPMENT Mirrors - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado

indicated by the ambient light sensor. With the gear selector lever in the REVERSE position,
backup lamp supply voltage is supplied as an input to the inside rearview mirror. The mirror
monitors this input to disable the automatic day-night feature. This allows the driver to see
objects in the mirror clearly when backing up, even during the night.

Compass

The mirror uses 2 magnetic field sensors for compass direction. One sensor is for north and south,
the other is for east and west. The mirror supplies a signal and low reference to each sensor. As
the vehicle travels with or against the earths magnetic pull, there will be a change in voltage on
one or both sensors. As a result of the change in voltage, the mirror changes the heading on the
compass display.

Temperature Display

The inside rearview mirror monitors the ambient air temperature sensor. As the outside air
temperature gets warmer, the ambient air temperature sensor will lower resistance. The inside
rearview mirror monitors this change and will show this as a warmer temperature on the display.
Temperatures exceeding 62°C (143°F) will be out of the mirror's temperature range and SC will
be shown on the temperature display. In colder outside air temperatures, the ambient air
temperature sensor will raise in resistance. The inside rearview mirror will show a colder
temperature on the display. Temperatures lower than -40°C (-40°F) will be out of the mirrors
temperature range which OC will be shown on the temperature display. In cold temperatures such
as 3°C (37°F) or below, the temperature display will show ICE when the ignition is first turned
ON. The display will toggle between ICE and the actual outside temperature until the
temperature update process is complete.

Temperature Display Update Process

The inside rearview mirror has a temperature program that takes in account the fact that the
radiator will heat the ambient air temperature sensor if the radiator is warm and the vehicle is not
moving. If the vehicle has been off for more than 2 hours, the mirror temperature program
assumes that the radiator has cooled and that the temperature supplied by the ambient air
temperature sensor is accurate. Because of this, if the vehicle has been off for more than 2 hours,
the mirror displays the temperature as reported by the ambient air temperature sensor. When the
ambient air temperature sensor reports a new temperature to the mirror, one of the following
cases will apply:

Ignition is OFF for more than 2 hours, then is turned ON for more than 3 minutes. The
outside temperature is greater than the last temperature recorded by the mirror for 2
minutes. The mirror will increase the last temperature reading by one degree every 2
minutes for 8 consecutive times. If the outside temperature is not matched after the 8th

2008 Chevrolet Silverado 1500

2008 ACCESSORIES & EQUIPMENT Mirrors - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado