Air Bag Terminology

Air Bag
The air bag is an inflatable cloth cushion that is designed to deploy in certain frontal crashes. It supplements the seatbelt protection by distributing the impact load more evenly over the vehicle occupant's head and torso.

B+
B+ is a battery voltage. This represents the battery voltage at the time of the indicated measurement. With the ignition switch ON and the engine not running, the system voltage will likely be between 11.5 and 12.5 volts. At engine idle, the voltage may be 14 to 16 volts. The voltage could be as low as 10 volts during engine cranking.

Bulb Check
Under normal operation this occurs when the ignition switch transitions from the OFF position to the RUN position. The inflatable restraint Diagnostic Energy Reserve Module (DERM) causes the AIR BAG warning lamp to flash seven times if no malfunctions are detected. The bulb test will also occur if IGNITION 1 voltage exceeds 17.1 volts and returns to the normal operating voltage range. The presents of a malfunction could prevent the DERM from flashing the warning lamp.

CKT
Circuit.

Continuous Monitoring
Test performed by the inflatable restraint Diagnostic Energy Reserve Module (DERM) on the SIR system during each 100 millisecond interval. The IGNITION 1 voltage at the DERM must be within the normal operating voltage range for continuous monitoring to occur. These tests follow the POWER-ON tests.

Datum Line
A base line parallel to the plane of the underbody or frame of the vehicle. All vertical measurements originate from this base line.

Deploy
To inflate the air bag.

Deployment Loop
The circuit that supply current to the inflatable restraint steering wheel inflator module to deploy the air bag.

Diagnostic Trouble Code (DTC)
A DTC is a 5 digit alpha numerical designator that is used by the inflatable restraint Diagnostic Energy Reserve Module (DERM) in order to indicate specific SIR system malfunctions. And DTC can be displayed and cleared on a scan tool.

Driver Current Source
An output of the inflatable restraint Diagnostic Energy Reserve Module (DERM) that supplies a low resistance path to ground for the inflatable restraint steering wheel inflator module circuit during the Initiator Assembly Resistance Test.

DVM or DVOM
Digital Volt Multimeter or Digital Volt Ohm Multimeter; J 39200.

Higher Priority Fault
Each diagnostic trouble code is assigned a priority. This priority is based on the detectability with other DTCs present. The priority only corresponds to the detectability of the malfunction. The priority does not relate to the critically of the malfunction with respect to deployment or non-deployment under any particular condition.

Ignition 1
A battery voltage (B+) circuit which is only powered with the ignition switch in the RUN or START positions.

Ignition Cycle
With the ignition switch ON, the voltage at the inflatable restraint Diagnostic Energy Reserve Module (DERM) Ignition 1 inputs is within the normal operating voltage range for at least ten seconds before turning the ignition switch OFF.

Inflatable Restraint Arming Sensor
The inflatable restraint arming sensor is on the high side (power side) of the deployment loop. The inflatable restraint arming sensor is calibrated to supply voltage to the inflatable restraint steering wheel inflator module when the velocity of the vehicle changes quickly enough to warrant arming the air bag. This is done in preparation for deployment.

Inflatable Restraint Arming Sensor Jumper Harness Connector
A 4-way connector that is located on the top of the LH side wheelhouse. It connects the front of the dash wiring harness to the inflatable restraint arming sensor jumper harness.

Inflatable Restraint Diagnostic Energy Reserve Module (DERM)
The module which provides reserve energy to the deployment loop. The DERM also performs diagnostic monitoring on all of the SIR system components.

Inflatable Restraint Discriminating Sensor
Intermediate Harness Connector.

A 4-way connector which is located on the top of the LH side wheelhouse. It connects the front of the dash wiring harness to the forward sensor harness.

Inflatable Restraint Steering Wheel Inflator Module
The inflatable restraint steering wheel inflator module is located in the steering wheel hub. The inflatable restraint steering wheel inflator module consists of the following components:
^ An inflatable bag
^ An inflator
^ An initiator

Inflatable Restraint Steering Wheel Module Coil
An assembly of 2 or more current-carrying coils mounted within the steering column hub. The assembly allows the rotation of the steering wheel while maintaining continuous electrical circuit contact. Two of the coils provide continuous contact of the driver deployment loop to the inflatable restraint steering wheel module.

Initiator
An electrical component that is inside the inflatable restraint steering wheel inflator module. When sufficient current flows, the inflatable restraint steering wheel inflator module sets off the chemical reaction which inflates the air bag.

Initiator Assembly Resistance Test
This test checks for the following items:
1. The correct inflatable restraint Diagnostic Energy Reserve Module (DERM) configuration for the vehicle
2. Shorts for Ignition 1 in the deployment loop
3. High resistance or opens in the Driver Side High and the Driver Side Low circuits
4. Measures the resistance of the inflator assembly.
The inflator assembly consists of the following items:
^ The initiator
^ The inflatable restraint steering wheel module coil
^ Connectors
^ Associated wiring
Each test is performed once per ignition cycle in which no malfunctions are detected during Turn-ON or Continuous Monitoring.

LH Forward Inflatable Restraint Discriminating Sensor
A sensor on the low side (ground side) of the deployment loop. The sensor is calibrated to supply ground to the inflatable restraint steering wheel inflator module when the vehicle velocity changes are severe enough to warrant the deployment of the air bag.

Normal Operating Voltage Range
The voltage that is measured between the inflatable restraint Diagnostic Energy Reserve Module (DERM) Ignition 1 terminal and the Ground terminals. The voltage should be between 7.25 and 16 volts.

RH Forward Inflatable Restraint Discriminating Sensor
A sensor on the low side (ground side) of the deployment loop. The sensor is calibrated to supply ground to the inflatable restraint steering wheel inflator module when the vehicle velocity changes are severe enough to warrant the deployment of the air bag.

Scan Tool
The scan tool is an off-board computer that is used in order to read diagnostic information from an on-board computer. This is done via the data link connector.

Serial Data
Serial data is information that represents the status of the SIR system.

SIR
The SIR is the Supplemental Inflatable Restraint.

SIR Wiring Harness
The SIR Wiring Harness is made up of the wires and the connectors which electrically connect the components in the SIR system.

System Voltage
The voltage that is available at the battery at the time at the indicated measurement. with the ignition switch ON and the engine not running, the system voltage will likely be between 11.5 and 12.5 volts. At idle, the voltage may be 14 to 16 volts. During engine cranking, the voltage could be as low as 10 volts.

Turn On
The inflatable restraint Diagnostic Energy Reserve Module (DERM) performs this test on the SIR system once during each ignition cycle. This is done immediately after Ignition 1 voltage is applied to the DERM and before Continuous Monitoring.

10 Minute Loop Test
The portions of the Initiator Assembly Resistance Rest that are repeated every ten minutes during an ignition cycle. This is the test that checks for shorts to Ignition 1 in the deployment loop.

36 Volt Loop Reserve (36 VLR)
This is the energy supply from the inflatable restraint Diagnostic Energy Reserve Module (DERM) which provides deployment power when the vehicle voltage is low or lost in a frontal crash.

36 VLR Delay
Charging of the 36 VLR power supply is inhibited briefly during Turn-ON. This allows the detection of certain malfunctions related to Ignition 1 voltage. These malfunctions cannot be tested with 36 volts present.