Chevrolet Silverado / GMC Sierra. Service manual — part 700

Fig. 98: Routing Wires To Apply Power For Controlled Bag Deployment (Right )
Courtesy of GENERAL MOTORS CORP.

30. Route the deployment harness out of the passenger's side of the vehicle.

31. Completely cover the windshield and the front door openings with a drop cloth.

32. Deploy each deployment loop one at a time.

33. Stretch out all of the deployment harness wires on the left and right side of the vehicle to

their full length.

34. Place a power source, 12 volt minimum/2 amp minimum, such as a vehicle battery, near the

shorted end of the harnesses.

35. Separate one set of wires and touch the wire ends to the power source in order to deploy the

seat belt pretensioners.

36. Disconnect the deployment harness from the power source and twist the wire ends together.

37. Continue the same process with the remaining deployment harnesses that are available.

38. Remove the drop cloth from the vehicle.

39. Disconnect all harnesses from the vehicle.

40. Discard the harnesses.

41. Scrap the vehicle in the same manner as a non-SIR equipped vehicle.

42. If one or more of the seat belt pretensioners did not deploy, perform the following steps to

remove the undeployed seat belt pretensioner from the vehicle, refer to Seat Belt

2008 Chevrolet Silverado 1500

2008 RESTRAINTS Supplemental Inflatable Restraints - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra &

Silverado

Retractor Pretensioner Replacement - Front (Regular Cab) or Seat Belt Retractor
Pretensioner Replacement - Front (Extended Cab) or Seat Belt Retractor
Pretensioner Replacement - Front (Crew Cab).

43. Call the Technical Assistance Group for further assistance.

DESCRIPTION AND OPERATION

SIR SYSTEM DESCRIPTION AND OPERATION

SIR System Overview

2008 Chevrolet Silverado 1500

2008 RESTRAINTS Supplemental Inflatable Restraints - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra &

Silverado

Fig. 99: Illustrating Deployed Inflatable Restraint
Courtesy of GENERAL MOTORS CORP.

The Supplemental Inflatable Restraint (SIR) System supplements the protection offered by the

2008 Chevrolet Silverado 1500

2008 RESTRAINTS Supplemental Inflatable Restraints - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra &

Silverado

occupants Seat Belt System (2). The SIR system may contain several inflator modules located
throughout the vehicle, i.e. steering wheel module (1) and instrument panel (I/P) module (1). In
addition to inflator modules, the vehicle contains an inflatable restraint Passenger Presence
System (PPS) that measures the weight of an occupant sitting in the front passenger seat. The PPS
uses the weight of the occupant to determine if the I/P inflator module will be enabled or
disabled. Each inflator module has a deployment loop that is controlled by the sensing and
diagnostic module (SDM) mounted inside the vehicle. The SDM determines the severity of a
collision with the assistance of various sensor inputs. When the SDM detects a collision of
sufficient force it will process the information provided by the sensors to further support air bag
deployment. The SDM performs continuous diagnostic monitoring of the SIR system electrical
components. Upon detection of a circuit malfunction, the SDM will set a DTC and inform the
driver by requesting the instrument panel cluster (IPC) to turn the AIR BAG indicator ON. The
steering column (1) and knee bolsters (3) are designed to absorb energy and compress during
frontal collisions in order to limit leg movement and decrease the chance of injury to the driver
and passenger.

Frontal SIR System Description

The frontal Supplemental Inflatable Restraint (SIR) System consists of the following components:

AIR BAG indicator located on the instrument panel cluster (IPC)

Driver and passenger knee bolsters

Inflatable restraint front end sensors (left/right)

Inflatable restraint PASSENGER AIR BAG ON/OFF indicator

Inflatable restraint Passenger Presence System (PPS)

Inflatable restraint passenger seat belt tension sensor

Inflatable restraint seat position sensor (SPS) (left)

Inflatable restraint sensing and diagnostic module (SDM)

Inflatable restraint steering wheel module

Inflatable restraint steering wheel module coil

Inflatable restraint wiring harnesses

Seat belt pretensioners (left/right)

Steering wheel and column

A frontal collision of sufficient force will deploy the frontal air bags. The SDM contains a
sensing device that converts vehicle velocity changes to an electrical signal. In the event of a
frontal collision, the SDM receives a signal from the front end sensors which assists the SDM in
determining the severity of some frontal collisions. The SDM contains a microprocessor that

2008 Chevrolet Silverado 1500

2008 RESTRAINTS Supplemental Inflatable Restraints - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra &

Silverado