Chevrolet Silverado / GMC Sierra. Service manual — part 1550

The body control module (BCM)

The driver information center (DIC)

The rear door lock/unlock relay (LBEC)

The door lock actuators in each of the doors

Door Lock System Controls

The power door lock system can be controlled by any of the following:

A power door lock or unlock switch activation

A keyless entry transmission

An automatic door lock function

A delay lock function

Door lock cylinder switch activation

Lockout Prevention

Power Door Lock System Operation

The front power door lock switches are integral components of the driver door module (DDS)
and passenger door module (PDS). The switches are 2 position normally open rocker switches.
When placed in either the lock or unlock positions, the switches provide a direct input to the
DDS or PDS. The DDS or PDS monitors these inputs and sends a GMLAN message indicating a
change in the switch's respective position. Modules which activate the power door lock actuators
receive the lock or unlock message and activate the actuator in the appropriate direction to lock
or unlock the vehicle's doors.

The modules which activate the power lock motors are:

The DDS (driver door lock actuator)

The PDS (passenger front door lock actuator)

The BCM (both rear door lock actuators)

The DDS and PDS are directly connected to the respective door lock actuator through the lock
and unlock control circuits. Once a door lock or unlock request has been received, the module
will supply battery voltage to one side of the actuator and ground the other causing the doors to
lock or unlock.

The rear passenger doors are controlled by the BCM through the rear door lock/unlock relay
which is incorporated onto the printed circuit board in the LH BEC. The BCM controls the

2008 Chevrolet Silverado 1500

2008 ACCESSORIES & EQUIPMENT Vehicle Access - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra &

Silverado

unlock relay by providing ground to energize the coil and controls the lock relay by providing
battery voltage to energize the relay coil. The energized the relay and allows voltage to be
applied to either the door lock motor lock or unlock circuits. Since the other side of the door
lock actuator is connected to the normally closed contacts of the opposing relay to ground, the
doors lock or unlock.

Programmable Automatic Door Locks

The automatic door lock feature can be programmed to control the door lock system. The
automatic door lock feature is factory programmed to have all doors lock and unlock.

When the automatic door lock feature is programmed to control the door lock system, the driver
door switch (DDS), passenger door switch (PDS) and body control module (BCM) will lock the
vehicle doors if the following inputs are true:

Ignition 1 input is active.

All door ajar switch inputs are inactive.

Transmission is shifted out of PARK.

This automatic door lock function will only occur once per ignition cycle unless, a door ajar
switch input changes state to active and back to inactive. Then the DDS, PDS and BCM will lock
all doors again.

Once the automatic door lock feature has locked the doors, the BCM will then unlock all the
doors when the transmission is shifted into PARK.

Lockout Prevention

This feature prevents the locking of the driver door if the ignition key is left in the ignition lock
cylinder. If a lock function occurs from any door lock switch and the body control module
(BCM) senses an active state on either the left front door latch signal, secondary door latch
switch signal and the key in ignition switch signal circuit is in the YES state, the BCM, driver
door switch (DDS) and passenger door switch (PDS) will lock the doors and then the DDS will
unlock the driver door.

Delayed Locking Operation

With any door open and a door lock switch is activated in the lock position, the driver door
switch (DDS), passenger door switch (PDS) and the body control module (BCM) will go into a
lock pending state. The BCM will also give 3 audible chimes. When the door is closed, the DDS,
PDS and the BCM will lock the doors after approximately 5 seconds. This feature can be

2008 Chevrolet Silverado 1500

2008 ACCESSORIES & EQUIPMENT Vehicle Access - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra &

Silverado

overridden by activating the door lock switch a second time and the doors will lock even with a
door open.

2008 Chevrolet Silverado 1500

2008 ACCESSORIES & EQUIPMENT Vehicle Access - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra &

Silverado

2008 DRIVELINE/AXLE

Propeller Shaft - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado

SPECIFICATIONS

FASTENER TIGHTENING SPECIFICATIONS

SEALERS, ADHESIVES, AND LUBRICANTS

COMPONENT LOCATOR

DRIVELINE DISASSEMBLED VIEWS

Application

Specification

Metric

English

Center Bearing Mounting Bolt

40 N.m

30 lb ft

Yoke Retainer Bolts

25 N.m

18 lb ft

Application

Type of Material

GM Part Number

Propeller Shaft Splines (Front Propeller
Shaft and One-Piece RWD Propeller Shaft
w/ Automatic Transmission)

Lubricant

12345879 or equivalent

meeting GM Specification

9985830

2008 Chevrolet Silverado 1500

2008 DRIVELINE/AXLE Propeller Shaft - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado

2008 Chevrolet Silverado 1500

2008 DRIVELINE/AXLE Propeller Shaft - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado