GM Malibu/Cutlass 1997-2000

General Information

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Driver's side and passenger air bags are standard equipment on all models covered by this guide. The Supplemental Inflatable Restraint (SIR) system offers protection in addition to that provided by the seat belt by deploying an air bag from the center of the steering wheel or dash panel. The air bag deploys when the vehicle is involved in a frontal crash of sufficient force up to 30° off the centerline of the vehicle. To further absorb the crash energy, there is also a knee bolster located beneath the instrument panel in the driver's area and the steering wheel is collapsible.



Click image to see an enlarged view

Fig. SIR system "deployment window"


WARNING
The system has an energy reserve, which can store a large enough electrical charge to deploy the air bag(s) for up to ten minutes after the battery has been disconnected or damaged. The system MUST be disabled before any service is performed on or around SIR components or SIR wiring.

SYSTEM OPERATION



The SIR deployment loop consists of the following components:



Sensing and Diagnostic Module (SDM)
 
Inflatable restraint steering wheel module
 
Inflatable restraint steering wheel module coil (SIR coil)
 
Inflatable restraint instrument panel module
 
AIR BAG warning lamp in the instrument cluster
 

The Sensing and Diagnostic Module (SDM), inflatable restraint steering wheel module coil (SIR coil assembly), inflatable restraint steering wheel module (driver inflator module), inflatable restraint instrument panel module (passenger inflator module), and connector wires make up the deployment loops. The function of the deployment loops is to supply current through the inflator modules, which will cause deployment of the air bags.

Deployment occurs when the SDM detects velocity changes severe enough to warrant deployment.

The SDM contains a sensing device (accelerometer) that converts vehicle velocity changes to an electrical signal. The SDM compares this signal to a value stored in memory. When the generated signal exceeds the stored value, the SDM performs additional signal processing and compares the generated signals to values stored in memory. When two of these generated signals exceed the stored values, the SDM will cause current to flow through the inflator modules, deploying the air bags.

SYSTEM COMPONENTS





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Fig. Supplemental Inflatable Restraint (SIR) system component views

Sensing and Diagnostic Module (SDM)

The Sensing and Diagnostic Module (SDM) performs the following functions in the SIR system:



Energy Reserve-The SDM maintains 23 Volt Loop Reserve (23 VLR) energy supplies to provide deployment energy. Ignition voltage can provide deployment energy if the 23 VLR malfunctions.
 
Frontal Crash Detection-The SDM monitors vehicle velocity changes to detect frontal crashes that are severe enough to warrant deployment.
 
Air Bag Deployment-During a frontal crash of sufficient force, the SDM will cause enough current to flow through the inflator modules to deploy the air bags.
 
Frontal Crash Recording-The SDM records information regarding the SIR system status during a frontal crash.
 
Malfunction Detection-The SDM performs diagnostic monitoring of the SIR system electrical components. Upon detection of a circuit malfunction, The SDM will set a Diagnostic Trouble Code (DTC).
 
Malfunction Diagnosis-The SDM displays SIR Diagnostic Trouble Codes (DTCs) and system status information through the use of a scan tool.
 
Driver Notification-The SDM warns the vehicle driver of SIR system malfunctions by controlling the AIR BAG warning lamp.
 

The SDM connects to the SIR wiring harness using a 12-way connector. The SDM harness connector uses shorting bar across certain terminals in the contact area. Removal of the SDM Connector Position Assurance (CPA) or harness connector itself will connect the AIR BAG warning lamp to ground through the shorting bar. The CPA is a small wedge-shaped plastic piece designed to lock the connector together.

The AIR BAG warning lamp will come ON steady with power applied to the SDM when either one of the following two conditions exist:



The SDM CPA is removed.
 
The SDM harness is disconnected.
 

The SDM receives power whenever the ignition switch is in the RUN or START positions.

AIR BAG Warning Lamp

The AIR BAG warning lamp is the key to driver notification of SIR system malfunctions.

The ignition switch applies ignition voltage to the AIR BAG warning lamp. The AIR BAG warning lamp receives power whenever the ignition switch is in the RUN or START positions. The SDM controls the lamp by providing ground with a lamp driver. The SIR system uses the AIR BAG warning lamp to do the following:



Verify lamp and SDM operation by flashing the lamp seven times when the ignition switch is first turned to the RUN position.
 
Warn the vehicle driver of SIR electrical system malfunctions which could potentially affect the operation of the SIR system. These malfunctions could either result in non-deployment in the case of a frontal crash, or deployment for conditions less severe than intended.
 

SIR Coil Assembly

The SIR steering wheel module coil assembly consists of two or more current carrying coils. They are attached to the steering column and allow rotation of the steering wheel while maintaining continuous deployment loop contact through the inflator module.

There is a shorting bar on the yellow 2-way connector near the base of the steering column that connects the steering wheel module coil to the SIR wiring harness. The shorting bar shorts the circuit when the connector is disengaged. The circuit to the inflator module is shorted in this way to prevent unwanted air bag deployment when servicing the steering column or other SIR components.

Inflator Module

The inflator module consists of an inflatable bag and an inflator (a canister of gas-generating material and an initiating device). When the vehicle is in a frontal crash of sufficient force to close the arming sensor and at least one discriminating sensor simultaneously, current flows through the deployment loop. Current passing through the initiator ignites the material in the inflator module, causing a reaction which produces a gas that rapidly inflates the air bag.

All vehicles are equipped with a driver's side inflator module located in the steering wheel and a passenger side inflator module located in the dash panel.

Steering Column

The steering column is energy absorbing. The steering column can compress during a frontal crash in order to decrease the chance of injury to the driver.

Knee Bolster

The knee bolsters absorb energy and control the forward movement of the vehicle's front occupants during a frontal crash by limiting leg movement.

SERVICE PRECAUTIONS





When performing service around the SIR system components or wiring, the SIR system MUST be disabled. Failure to do so could result in possible air bag deployment, personal injury or unneeded SIR system repairs.
 
When carrying a live inflator module, make sure that the bag and trim cover are pointed away from you. Never carry the inflator module by the wires or connector on the underside of the module. In case of accidental deployment, the bag will then deploy with minimal chance of injury.
 
When placing a live inflator module on a bench or other surface, always face the bag and trim cover up, away from the surface.
 



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Fig. When carrying a live inflator module, make sure that the bag and trim cover are pointed away from you. Never carry the inflator module by the wires or connector on the underside of the module



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Fig. Follow all the manufacturer's cautions when working on an air bag equipped vehicle

DISABLING THE SYSTEM




NOTE
With the "AIR BAG" fuse removed and the ignition switch ON , the "AIR BAG" warning lamp will be on. The is normal and does not indicate any system malfunction.

  1. Turn the steering wheel so that the vehicle's wheels are pointing straight ahead.
  2.  
  3. Turn the ignition switch to LOCK , remove the key, then disconnect the negative battery cable.
  4.  
  5. Remove the "AIR BAG" fuse from the instrument panel left end (driver's) fuse box.
  6.  



Click image to see an enlarged view

Fig. Remove the "AIR BAG" fuse (F) from the fuse box located at the left end (driver's side) of the instrument panel


NOTE
With the AIR BAG fuse removed and the ignition switch in the RUN position, the warning lamp will be lit. This is normal and does not indicate SIR malfunction.

  1. Remove the Connector Position Assurance (CPA) from the yellow two way connector located above the driver's fuse box. The CPA is a small wedge-shaped plastic piece designed to lock the connector together. Disconnect the yellow two way connector (1)
  2.  



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Fig. To disable the driver's side airbag, remove the CPA (2) from the yellow 2-way connector (1) located above the driver's fuse box, then unplug the yellow 2-way connector (1)

  1. Repeat steps 3 and 4 for the fuse box at the right end (passenger side) of the instrument panel.
  2.  



Click image to see an enlarged view

Fig. To disable the passenger's side airbag, remove the CPA (2) from the yellow 2-way connector (3) located above the passenger's side fuse box, then unplug the yellow 2-way connector (3)

  1. Connect the negative battery cable.
  2.  

ENABLING THE SYSTEM



  1. Turn the ignition switch to LOCK , then remove the key.
  2.  
  3. Disconnect the negative battery cable.
  4.  
  5. Connect the yellow 2-way connector located above the driver's side fuse box.
  6.  
  7. Install the Connector Position Assurance (CPA) to the yellow 2-way connector located above the driver's fuse box.
  8.  
  9. Repeat steps 3 and 4 for the passenger side fuse box.
  10.  
  11. Install the "AIR BAG" fuse to the driver's fuse block.
  12.  
  13. Connect the negative battery cable.
  14.  


CAUTION
Stay well away from both AIR BAGS when turning the ignition key to RUN.

  1. Turn the ignition switch to RUN and make sure that the "AIR BAG" warning lamp flashes seven times and then shuts off. If the warning lamp does not shut off, make sure that the wiring is properly connected. If the light remains on, take the vehicle to a reputable repair facility for service.
  2.  

 
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