Safety System Repair Basics (Part 5 of 5) – Impact Sensor Replacement Guidelines

| July 13, 2015
 

Impact Sensor CloseupThe impact sensor replacement policy requires replacing sensors in the area of the accident damage. The area of accident damage is defined as the portion of the vehicle which is crushed, bent or damaged due to a collision. An example of this would be a moderate collision where the front of the vehicle strikes an object. If the vehicle has an impact sensor mounted forward of the radiator, it must be replaced.

  • Replace the impact sensor whether or not the air bags have deployed.
  • Replace the impact sensor even if it appears to be undamaged.
  • Verify the correct replacement part number. Do not substitute a component from a different vehicle.
  • Use only original GM replacement parts available from your authorized GM dealer. Do not use salvaged parts for repairs to the SIR system.

Impact Sensor SmallImpact sensor damage, which is not visible, such as slight bending of the mounting bracket or cuts in the wire insulation, can cause improper operation of the SIR system. Do not try to determine whether the impact sensor is undamaged. Instead, replace the impact sensor. Also, if you follow a diagnostic trouble code (DTC) procedure and a malfunctioning impact sensor is indicated, replace
the impact sensor.

SIR Disabling and Enabling
SIR component location affects how a vehicle should be serviced. There are parts of the SIR system installed in various locations around a vehicle. To find the location of the SIR components, refer to GM Service Information, available for purchase at http://www.acdelcotechconnect.com/shop-program/psc-program/gm-service-information/

The following information covers the proper procedures for disabling/enabling the SIR system.

Impact Sensor Repair 5 of 5

SIR Service Precautions
Warning: When performing service on or near the SIR components or the SIR wiring, the SIR system must be disabled. Failure to observe the correct procedure could cause deployment of the SIR components. Serious injury can occur. Failure to observe the correct procedure could also result in unnecessary SIR system repairs. The Inflatable Restraint Sensing and Diagnostic Module (SDM) maintains a reserved energy supply. The reserved energy supply provides deployment power for the air bags if the Inflatable Restraint Sensing and Diagnostic Module loses battery power during a collision. Deployment power is available for as much as 2 minutes after disconnecting the vehicle power.

Waiting 2 minutes before working on the system after
disabling the SIR system prevents deployment of the air
bags from the reserved energy supply.

Disabling Procedure – Air Bag Fuse
1. Turn the steering wheel so that the vehicle’s wheels
are pointing straight ahead.

2. Place the ignition in the OFF position. Warning: The SDM may have more than one fused power input. To ensure there is no unwanted SIR deployment, personal injury or unnecessary SIR system repairs, remove all fuses supplying power to the SDM. With all SDM fuses removed and the ignition switch in the ON position, the AIR BAG warning indicator illuminates. This is normal operation and does not indicate an SIR system malfunction.

3. Locate and remove the fuse(s) supplying power to the Inflatable Restraint Sensing and Diagnostic Module. Refer to SIR Schematics or Electrical Center Identification Views in the GM Service Information.
4. Wait 2 minutes before working on the system.

Enabling Procedure – Air Bag Fuse

1. Place the ignition in the OFF position.
2. Install the fuse(s) supplying power to the Inflatable Restraint Sensing and Diagnostic Module. Refer to SIR Schematics or Electrical Center Identification Views in the GM Service Information.
3. Turn the ignition switch to the ON position. The AIR BAG indicator will illuminate or flash then turn OFF.
4. Perform the Diagnostic System Check – Vehicle if the AIR BAG warning indicator does not operate as described. Refer to Diagnostic System Check – Vehicle in the GM Service Information.

Disabling Procedure – Negative Battery Cable
1. Turn the steering wheel so that the vehicle’s wheels are pointing straight ahead.
2. Place the ignition in the OFF position.
3. Disconnect the negative battery cable from the battery.
4. Wait 2 minutes before working on system.

Enabling Procedure – Negative Battery Cable
1. Place the ignition in the OFF position.
2. Connect the negative battery cable to the battery.
3. Turn the ignition switch to the ON position. The AIR BAG indicator will illuminate or flash, then turn OFF.
4. Perform the Diagnostic System Check — Vehicle if the AIR BAG warning indicator does not operate as described. Refer to Diagnostic System Check – Vehicle in the GM Service Information.

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Category: The Technical Side