Definitions/Abbreviations

AIR BAG
An inflatable cloth cushion designed to deploy in certain frontal crashes. It supplements safety belt by distributing the impact load more evenly over the vehicle occupant's head and torso.

ARMING SENSOR
A sensor on the deployment loop's high side (or power side) that is calibrated to supply voltage to the inflater module when vehicle velocity changes are severe enough to warrant air bag arming. The arming sensor Is contained in the dual sensor.

"CONTINUOUS MONITORING"
SIR system tests performed by the DERM every 100 milliseconds while Ignition 1 voltage is present at the DERM.

DATA LINK
A signal wire used for communications between multiple on-board computers or from an on-board computer to an off-board computer.

DATUM LINE
A base line parallel to the plane of the underbody or frame from which all vertical measurements originate.

DEPLOY
To inflate the air bag.

DEPLOYMENT LOOP
The circuits which supply current to the inflater module to deploy the air bag.

DERM
Diagnostic Energy Reserve Module which provides reserve energy to the deployment loop and diagnostic monitoring of all system components.

DLC
Data Link Connector - formerly ALDL connector.

DTC
Formerly "Code," a numerical designator used by the DERM to indicate specific SIR system faults.

DUAL SENSOR
A switch housing containing the arming sensor and the passenger compartment discriminating sensor.

FORWARD DISCRIMINATING SENSOR
A sensor on the deployment loop's ground side (or low side) that is calibrated to ground the inflater module when vehicle velocity changes are severe enough to warrant air bag deployment

EEPROM
Electrically Erasable Programmable Read Only Memory.

FORCE HI
A DERM output which injects current into the steering column circuit during the "Steering Column Resistance" tests.

FORCE LOW
A DERM input which grounds the steering column circuit during the "Steering Column Resistance" tests.

INFLATOR MODULE
An assembly located in the steering wheel hub beneath the vinyl trim cover consisting of an inflatable bag, an inflater and an initiator.

INITIATOR
The electrical component inside the inflater module which, when sufficient current flows, sets off the chemical reaction that Inflates the air bag.

NON-POWERED PROBE TYPE TESTER
Test lamp.

PASSENGER COMPARTMENT DISCRIMINATING SENSOR
A sensor on the deployment loop's ground side (or low side) that is calibrated to ground the inflater module when vehicle velocity changes are severe enough to warrant air bag deployment. It is contained in the dual sensor.

RESISTOR MODULE
A resistor assembly in the SIR harness between the DERM and steering wheel. It allows the DERM to monitor the deployment loop for faults and detects when a vehicle frontal crash has occurred.

SCAN TOOL
Tool used to read diagnostic information from the DERM via the DLC.

SENSE HI
A DERM input on the deployment loop's high side which is monitored for fault detection.

SENSE LOW
A DERM Input on the deployment loop's low side which is monitored for fault detection.

SIR
Supplemental Inflatable Restraint.

SIR COIL
A current-carrying coil in the deployment loop that allows steering wheel rotation, while maintaining continuous deployment loop contact through the inflater module.

SIR WIRING HARNESS
The wires and connectors that electrically connect together the SIR system components.

"STEERING COLUMN RESISTANCE"
Inflator module, SIR coil and steering column wiring tests, which the DERM performs once each ignition cycle when no faults are detected during "Turn-on" or "Continuous Monitoring."

SYSTEM VOLTAGE
Battery voltage available at the time of an indicated voltage measurement. With the key on and engine not running, the system voltage will likely be between 12 and 12.5 volts. At idle, the voltage may be 14 to 16 volts. The voltage could be as low as 10 volts during engine cranking.

"TURN-ON"
SIR system tests which the DERM performs once during each ignition cycle, immediately after "Ignition 1 " voltage is applied to the DERM.

36 VLR
The 38 Volt Loop Reserve energy supply from the DERM which provides deployment power when vehicle voltage is low or is lost in an accident.