Air Bag Restraint System Buick LeSabre VII

IDENTIFICATION

All models equipped with a Supplemental Inflatable Restraint (SIR) system have a number "2" (driver and passenger-side air bags) or "3" (driver-side air bag only) in the seventh position of the Vehicle Identification Number (VIN). Some vehicles have the words Supplemental Inflatable Restraint or SIR on the inflator module. Steering wheel hub is slightly larger in order to accommodate the driver-side air bag.

SUPPLEMENTAL INFLATABLE RESTRAINT (SIR) SYSTEM

The Supplemental Inflatable Restraint (SIR) system is designed to protect the driver and passenger (if equipped) in a frontal collision. The air bag(s) will deploy only upon frontal or near frontal impact of no more than 30 degrees off the center line of vehicle. System is not designed to deploy in rear impacts, side impacts, or rollovers. A frontal impact of sufficient severity (comparable to a collision into a solid wall at approximately 14 MPH or more) will cause sensors in vehicle to detect this sudden deceleration. These sensors, in turn, trigger the inflator module(s).

Note. Following SIR components are not necessarily installed on all vehicles.

SENSING & DIAGNOSTIC MODULE (SDM)

Vehicles not equipped with a DERM are equipped with a Sensing and Diagnostic Module (SDM).

SDM contains a sensing device which converts vehicle velocity changes to an electrical signal. The electrical signal generated is processed by SDM and compared to a value stored in memory. When generated signal exceeds stored value, additional signal processing is performed, and generated signals are compared to value stored in memory. When 2 generated signals exceed stored values, or when one generated signal exceeds stored value and forward discriminating sensor closes, SDM will close circuit, providing voltage to inflator module.

SDM is designed to provide following functions in SIR system

Energy Reserve

SDM maintains a 36-Volt Loop Reserve (36VLR) energy supply for 2 minutes to provide deployment energy when ignition voltage is lost in a frontal crash.

Frontal Crash Detection

SDM monitors vehicle velocity changes to detect frontal crashes which are severe enough to cause deployment.

Air Bag Deployment

When a frontal crash of sufficient force is detected, SDM will close circuit, deploying air bags.

Frontal Crash Recording

SDM records information regarding SIR system status during a frontal crash.

Malfunction Detection

SDM performs diagnostic monitoring of SIR system electrical components and sets a diagnostic trouble code when malfunction is detected.

Malfunction Diagnosis

SDM displays SIR diagnostic trouble codes and system status information via a scan tool.

Driver Notification

SDM warns driver of SIR system malfunction by controlling AIR BAG warning light.

SDM is connected to SIR wiring harness by a 20-pin connector. Harness connector utilizes a shorting bar across certain terminals in contact area. Shorting bar connects AIR BAG warning light to ground when SDM harness connector is disconnected. This causes AIR BAG warning light to come on steady whenever ignition is on.

AIR BAG RESTRAINT WARNING LIGHT

Note. Some vehicles have an INFLATABLE RESTRAINT warning light as opposed to an AIR BAG warning light.

When ignition switch is in RUN, BULB TEST, or START positions, battery voltage is applied to AIR BAG warning light. DERM/SDM illuminates this light by providing a ground to a lamp driver. Some vehicles are equipped with a Serial Data Controlled Warning Lamp (SDCWL). An SDCWL equipped vehicle utilizes a smart cluster which communicates via the serial data line, so in this case, DERM/SDM transmits a request to turn on AIR BAG warning light. When ignition is first turned on, AIR BAG warning light verifies light and DERM/SDM operation by flashing 7-9 times. Light is also used to warn driver of SIR electrical system faults which could potentially affect SIR system operation. AIR BAG warning light is the key to driver notification of SIR system faults.

In addition, the light provides diagnostic information by flashing Diagnostic Trouble Codes (DTCs) when the flash code diagnostic mode is entered on models without on-board diagnosis. INFLATABLE RESTRAINT indicator light notifies driver of SIR system faults.

ARMING SENSOR/DUAL POLE ARMING SENSOR

Arming sensor/dual pole arming sensor is a protective switch located in power feed side (positive side) of deployment loop. It is calibrated to close at low-level velocity changes (lower than discriminating sensors). This assures that each inflator module is connected directly to 36VLR output of DERM or ignition voltage when either of the discriminating sensors close.

Arming sensor/dual pole arming sensor consists of a sensing element, normally open switch contacts, a diagnostic resistor, and 2 diodes. Sensing element closes switch contacts when velocity of vehicle changes at a rate indicating potential need for deployment. A diagnostic resistor is connected in parallel with normally open switch contacts and allows for a small amount of current flow through deployment loop during normal undeployed conditions. This small current flow results in voltage drops across each component within loop.

DERM monitors these voltage drops to detect circuit or component faults. The 2 diodes provide isolation between 36VLR output of DERM and ignition voltage. In some vehicles, arming sensor is combined with passenger compartment discriminating sensor.

DISCRIMINATING SENSORS

Most SIR systems have 2 discriminating sensors. Some vehicles have 2 forward discriminating sensors, while other vehicles have one forward discriminating sensor and a passenger compartment discriminating sensor, or 2 mid-rail discriminating sensors. Forward discriminating sensor is located on radiator support brace or tie bar. Passenger compartment discriminating sensor is located under center of instrument panel/console area or under front passenger seat. Mid-rail discriminating sensors are located on side mid-rails in engine compartment.

In some vehicles, the passenger compartment discriminating sensor is combined with arming sensor. Discriminating sensors are wired in parallel on the ground side of deployment loop. These sensors are calibrated to close when deceleration velocity changes are severe enough to warrant deployment.

Sensors consist of a sensing element, normally open switch contacts, and a diagnostic resistor. Sensing element closes the normally open switch contacts when vehicle velocity changes are severe enough to warrant deployment.

A diagnostic resistor is connected in parallel with the normally open switch contacts within each of the sensors. These parallel resistors supply the ground path for current passing through the deployment loop during normal undeployed conditions. This small current flow results in a voltage drop across each component within loop. DERM monitors these voltage drops to detect circuit or component faults.

SIR COIL ASSEMBLY

SIR coil assembly consists of 2 current-carrying coils. It is installed in steering column and allows rotation of steering wheel while maintaining continuous (directly wired) contact of deployment loop through steering wheel inflator module. Slip rings are not used in SIR system to transmit current from column to steering wheel.

Gold-plated terminals and a shorting bar are used on coil assembly lower steering column Yellow connector. Shorting bar shorts the circuits to main coil and steering wheel inflator module when lower steering column connector is disconnected. This shorts the circuit to the inflator module(s), preventing unwanted deployment of the air bag(s) when servicing the steering column or other SIR components.

INFLATOR MODULE

When the vehicle is in an accident of sufficient force to simultaneously close the arming sensor and at least one discriminating sensor, nitrogen gas inflates the cloth bag packed inside the steering wheel hub and in passenger-side instrument panel, (if equipped). The bag(s) inflate in less than 1/20 of a second. As air bag is contacted by driver or passenger, the gas is vented through openings in the bag, which deflates almost as soon as it is completely deployed.

RESISTOR MODULE

Resistor module is located in SIR harness between inflator module and DERM. Resistor module allows DERM to monitor deployment loop for faults and to detect when a deployment has occurred.

Resistors in resistor module are balanced with resistors on arming and discriminating sensors to allow DERM to monitor voltage drops across the components of the deployment loop. Faults are detected during normal undeployed conditions by monitoring these voltages. On some vehicles, resistor module is mounted on DERM.

SYSTEM OPERATION CHECK

If system is functioning normally, air bag warning light flashes 7-9 times when ignition switch is turned to ON position and goes out.

Four possible warning light conditions can indicate a system failure

1. Light does not illuminate at all.
2. Light comes on while vehicle is driven.
3. Light flashes 7-9 times, and remains on.
4. Light does not flash but remains lit when ignition is turned on.

SIR system faults are usually due to a disconnected/loose electrical connector caused by previous service on vehicle. Always check Yellow SIR connector at base of steering column for loose or damaged wiring.

POST-COLLISION INSPECTION

When a vehicle has been involved in a collision, certain components of the passive restraint system must be inspected or replaced. See PASSIVE RESTRAINT SYSTEM INSPECTION article in the GENERAL INFORMATION section for post-collision inspection information.

All SIR components, including harness and brackets, must be inspected after an accident. Replace any damaged or bent components, even if a deployment did not occur. Check steering column, knee bolster, instrument panel steering column reinforcement plate, right side instrument panel supports, and all braces for damage. DO NOT service forward discriminating sensor, passenger compartment discriminating sensor, arming sensor, DERM/SDM, coil assembly, or inflator module(s). These components require replacement. System wiring harness can only be serviced with splice sleeves in Wire Repair Kit (J-38125-A). If wiring pigtail of sensor runs through area of accident damage but sensor case/bracket is not damaged, sensor should still be replaced.

INTERMITTENTS & POOR CONNECTIONS

Most intermittents are caused by faulty electrical connections or wiring, or a sticking relay or solenoid. Items to check are

1. Poor mating or connector halves, or terminals not fully seated in connector
2. Dirt or corrosion on terminals. Terminals must be clean and free of any foreign material which could impede proper terminal contact.
3. Damaged connector, exposing the terminals to dirt and moisture, as well as not maintaining proper terminal orientation with the component or mating connector.
4. Improperly formed or damaged terminals. All connector terminals in problem circuit(s) should be checked carefully to ensure good contact.
5. Connector Test Adapter Kit (J-35616-A) must be used whenever a diagnostic procedure requests checking or probing a terminal. Using adapter will ensure that no damage to terminals will occur, as well as giving an idea whether contact is sufficient.
6. Poor terminal-to-wire connections. some conditions which fall under this description are poor crimps, poor solder joints, crimping over wire insulation rather than the wire itself, or corrosion in the wire-to-terminal contact area.
7. Wire Insulation which is rubbed through, causing an intermittent short as the bare area touches other wiring or parts of vehicle.
8. Broken wires inside insulation. Perform continuity check while flexing wiring harness to find location of broken wires.

SYSTEM REPAIR

Before any repairs are performed, disconnect and shield battery ground. Because system has ability to retain voltage, remove SIR or AIRBAG fuse, and disconnect Yellow SIR connector at base of steering column, and, on vehicles with passenger-side air bags, disconnect Yellow SIR connector at base of right instrument panel (behind knee bolster).

Wait 2 minutes before working on vehicle. All connectors used on SIR system use Connector Position Assurance (CPA) clips to ensure connector retention. Even if system is disconnected, always use caution when working near inflator modules.

SENSOR HANDLING

Use special care when handling a sensor. DO NOT strike or jar a sensor, as air bag deployment, personal injury or improper operation of SIR system could result. A sensor must be replaced if dropped 3 feet or more. Sensors and mounting bracket bolts must be carefully torqued to ensure correct operation. Never power up SIR system when any sensor is not rigidly attached to vehicle, since sensor is easily activated and could cause air bag deployment.

LIVE INFLATOR MODULE HANDLING

When carrying a live inflator module, ensure bag and trim cover are pointed away from body. If an accidental deployment occurs, bag will then deploy with reduced chance of injury. When placing a live inflator module on a bench or other surface, always face bag and trim cover up and away from surface so space is provided to allow air bag to expand in case of deployment. In addition, never carry any SIR component by wires or connector.

SPECIAL TOOLS

To avoid deployment when working on SIR system, DO NOT use electrical test equipment such as test lights, battery or A/C-powered volt/ohmmeter, or any type of electrical equipment other than those specified by manufacturer. See SIR RECOMMENDED TOOLS table.

SIR RECOMMENDED TOOLS

DISABLING & ACTIVATING AIR BAG SYSTEM

DISABLING SYSTEM

1. Turn steering wheel to place vehicle wheels in straight-ahead position. Turn ignition switch to LOCK position.
2. Remove SIR or AIRBAG fuse. Remove CPA clip and disconnect Yellow SIR connector at base of steering column (it may be necessary to remove left sound insulator). If equipped with passenger-side air bag, disconnect Yellow SIR connector under right instrument panel or behind glove box door assembly. Some models have access to connector through a trap door in glove box.
3. Wait 2 minutes before beginning service. All connectors in SIR system use CPA clips to ensure connector retention. Even if system is disconnected, use caution when working near air bags.

ACTIVATING SYSTEM

Connect Yellow SIR connector at base of steering column, and under right side instrument panel, if equipped. Install CPA clips and fuse. Turn ignition switch to RUN position and ensure AIR BAG warning light flashes 7-9 times and then goes out.

Scheme 1

1. If coil assembly has been removed from steering column and is being reinstalled, go to next step. New coil assemblies are provided pre-centered and include a Blue plastic tab that is snapped off once coil is installed. (Scheme 1)
2. Ensure front wheels face straight ahead when installing or removing a coil assembly. If coil is removed without wheels in straight-ahead position and steering wheel has not been moved, same coil can be reinstalled if coil hub has not been rotated.
3. Hold coil assembly with clear bottom upward to see coil ribbon. Note there are 2 different styles of coil assemblies: one rotates clockwise and other counterclockwise.
4. While holding coil assembly housing, depress spring lock and rotate hub in direction of arrow until it stops. Coil assembly should now be wound up snug against center hub. Rotate coil assembly hub in opposite direction approximately 2 1/2 turns. Release spring lock between locking tabs in front of arrow.

DISPOSAL PROCEDURES

DEPLOYED AIR BAG

Once an inflator module has been deployed, surface of air bag may contain a small amount of sodium hydroxide dust, combined with a White packing powder. Sodium hydroxide dust can be irritating to skin if left on for an extended period of time. Always wear gloves and safety glasses when handling a deployed inflator module. Wash hands with mild soap and water afterward. Deployed air bag modules can be disposed of as would any other part. Handle air bag module with gloves, and wear safety glasses.

UNDEPLOYED AIR BAG

Undeployed air bag modules must not be disposed of at normal refuse locations. Undeployed air bag modules contain substances which can cause illness or injury if handled improperly. Disposal of air bag module in any manner inconsistent with proper procedures may be a violation of federal, state and/or local laws. If possible, deploy air bag module in vehicle. See SCRAPPED VEHICLE.

Transportation of undeployed inflator modules is regulated by hazardous materials regulations of U.S. Government Department of Transportation and most state governments. Special shipping procedures must be followed. Check with hazardous material section of state government for applicable shipping requirements.

SCRAPPED VEHICLE

Some vehicles which have to be scrapped may have undeployed SIR systems. When scrapping a vehicle with an undeployed module

1. Turn ignition switch to OFF position. Remove SIR fuse. Disconnect Yellow 2-pin connector at base of steering column. Cut harness side of SIR wiring approximately 3-6" from Yellow 2-pin connector.
2. Splice 2 wires at least 20 feet long to wiring cut from SIR harness. Connect Yellow 2-pin connector.
3. Ensure inflator module is secured to steering wheel. Remove all loose objects from front seat, and ensure no one is in vehicle. Stretch wires away from car as far as possible.
4. Connect wires to a 12-volt battery. Air bag should deploy. DO NOT touch inflator module area for 20 minutes due to heat generated during deployment. Wear gloves and safety glasses before handling deployed air bag. Wash hands with mild soap and water afterward.
5. On vehicles with passenger-side air bags, repeat deployment procedure for passenger-side. Access Yellow 2-pin connector at base of right instrument panel (behind knee bolster) or behind glove box door assembly.

REMOVAL & INSTALLATION

Removal

1. Before proceeding, follow air bag service precautions. See SERVICE PRECAUTIONS. Disable air bag system. See DISABLING & ACTIVATING AIR BAG SYSTEM.
2. SDM is located under passenger seat. Remove passenger seat and right front sill plate. Lift carpet and sound deadener. Unplug CPA clip and electrical connector. Unbolt SDM and remove it. (Scheme 2)

Scheme 2

Installation

Connect electrical connector and CPA clip to SDM module. Replace fasteners and torque to 75 INCH Lbs. (8.5 N.m). Replace carpet and sound deadener. Reinstall right front sill plate and passenger seat. Reactivate air bag system. See DISABLING & ACTIVATING AIR BAG SYSTEM. Check AIR BAG warning light to ensure system is functioning correctly. See SYSTEM OPERATION CHECK.

1. Before proceeding, follow air bag service precautions. See SERVICE PRECAUTIONS. Disable air bag system. See DISABLING & ACTIVATING AIR BAG SYSTEM.
2. Forward discriminating sensor is located next to hood latch bracket. Remove sensor mounting bolts. Remove CPA clip and electrical connector. Remove fasteners from upper radiator tie bar to grille (as necessary). Remove sensor bolts and sensor. (Scheme 3)

Scheme 3

1. Align sensor to vehicle, ensuring arrow on sensor body is facing toward front of vehicle. Install and torque sensor bolts to 8.9 Ft. Lbs. (12 N.m.) and reinstall connector and CPA clip.
2. Reactivate air bag system. See DISABLING & ACTIVATING AIR BAG SYSTEM. Check AIR BAG warning light to ensure system is functioning properly. See SYSTEM OPERATION CHECK.

1. Before proceeding, follow air bag service precautions. See SERVICE PRECAUTIONS. Disable air bag system. See DISABLING & ACTIVATING AIR BAG SYSTEM.
2. Remove inflator module. See INFLATOR MODULE under REMOVAL & INSTALLATION. Remove horn contact wire from steering column. Remove steering wheel hexagonal locking nut. Using appropriate puller, remove steering wheel. See STEERING WHEEL PULLER SPECIFICATIONS table.

STEERING WHEEL PULLER SPECIFICATIONS

Note. Front wheels of vehicle must be turned to straight-ahead position before beginning service. Failure to do so can result in coil assembly being removed without being centered. Reinstalling coil assembly under such circumstances causes ribbon in coil assembly to break when steering wheel is turned fully in one direction. Ensure key is always in LOCK position to prevent wheel from turning and uncentering coil assembly. To re-center coil assembly, see CENTERING COIL ASSEMBLY under ADJUSTMENTS.

1. Before proceeding, follow air bag service precautions. See SERVICE PRECAUTIONS. Disable air bag system. See DISABLING & ACTIVATING AIR BAG SYSTEM.
2. Remove inflator module. See INFLATOR MODULE under REMOVAL & INSTALLATION. Remove horn contact wire from steering column. Remove steering wheel. See STEERING WHEEL under REMOVAL & INSTALLATION. DO NOT install puller bolts too far, as damage to coil assembly can result.
3. Remove coil assembly retaining ring from steering shaft. Grasp clear plastic wire protector shield on underside of steering column, and slide downward. Partially remove coil assembly from end of steering wheel shaft and allow coil to hang freely. Note orientation to steering column housing before removal.
4. Remove wave washer from steering shaft. Using Lock Plate Compressor (J-23653-C), depress shaft lock and remove shaft lock retaining ring. Remove shaft lock plate and upper bearing spring. Remove turn signal canceling cam.
5. Remove hazard knob and attaching screw. Remove turn signal switch arm. Remove 3 turn signal switch screws and partially withdraw switch. Disconnect any remaining electrical connectors. Attach mechanics wire to coil assembly lower connector at base of steering column and carefully pull wire through gear shift lever bowl, column housing and lock housing cover.

1. Carefully feed coil assembly wire and lower connector through lock housing cover, column housing, and gear shift lever bowl. Allow coil assembly to hang freely. NOTE: Use care not to pinch wires when installing components. After wire is fed through, attach CAUTION tag to wire near connector at base of steering column. Tag is included in coil assembly repair kit.
2. Install turn signal switch and torque screws to 30 INCH Lbs. (3.4 N.m). Install turn signal switch arm and torque attaching screw to 20 INCH Lbs. (2.3 N.m).
3. Install hazard knob and attaching screw. Install turn signal canceling cam and shaft lock plate. Install shaft lock retaining ring. Using lock plate compressor, align block tooth on shaft, and depress shaft lock plate. Install wave washer.
4. Ensure coil assembly hub and steering shaft are centered. Coil assembly will become uncentered if column is separated from steering gear and is allowed to rotate, or if centering spring is depressed, allowing hub to rotate while coil assembly is removed from column.
5. Install coil assembly, using horn tower on canceling cam to align hole on inner ring of coil and projections on steering column housing with projections on outer ring of coil. To complete installation, reverse removal procedure.
6. Reactivate air bag system. See DISABLING & ACTIVATING AIR BAG SYSTEM. Check AIR BAG warning light to ensure system is functioning properly. See SYSTEM OPERATION CHECK.

Removal (Driver-Side)

1. Before proceeding, follow air bag service precautions. See SERVICE PRECAUTIONS. Disable air bag system. See DISABLING & ACTIVATING AIR BAG SYSTEM.
2. Remove screws and nuts from underside of steering wheel. Partially remove inflator module and disconnect steering wheel inflator module connector, and CPA clip. Disconnect horn contact from inflator. Remove radio control switch connector, if equipped. Remove inflator module.

Installation (Driver-Side)

1. Install horn contact, steering wheel inflator module connector, and CPA clip. Install inflator module to steering wheel. Tighten inflator module screws to proper specification. See TORQUE SPECIFICATIONS.
2. To complete installation, reverse removal procedure. Reactivate air bag system. See DISABLING & ACTIVATING AIR BAG SYSTEM. Check AIR BAG warning light to ensure system is functioning properly. See SYSTEM OPERATION CHECK.

Removal (Passenger-Side)

1. Before proceeding, follow air bag service precautions. See SERVICE PRECAUTIONS. Disable air bag system. See DISABLING & ACTIVATING AIR BAG SYSTEM.
2. Remove instrument panel assembly. Remove fasteners from passenger inflator module and remove module. (Scheme 4)

Scheme 4

Installation (Passenger-Side)

1. Reinstall inflator module and fasteners. Torque nuts to 89 INCH Lbs. (10 N.m.). Install instrument panel assembly.
2. Reactivate air bag system. See DISABLING & ACTIVATING AIR BAG SYSTEM. Check AIR BAG warning light to ensure system is functioning properly. See SYSTEM OPERATION CHECK.

DIAGNOSIS & TESTING

Diagnostic Trouble Codes (DTCs)

Diagnostic Energy Reserve Module (DERM) provides a record of DTCs stored according to type. Current DTCs are faults presently being detected. Current DTCs are stored in Random Access Memory (RAM) and are erased when fault is corrected. Current DTCs can be read using a scan tester such as Tech 1, or on-board diagnostics on Cadillac vehicles.

Scan Tester Diagnostics

A scan tester will read and clear current codes and history codes. Ensure scan tester contains correct cartridge for SIR diagnostics. To use scan tester, connect it to DLC connector, plug in power source and turn ignition switch to ON position. Follow scan tester manufacturer instructions for communication with SIR system. Scan tester reads serial data from DERM data link output to DLC connector.

On-Board Diagnostics

On-board diagnostics can only be used on Cadillac models which have an on-board diagnostics panel. Enter diagnostics by depressing WARMER and OFF buttons on diagnostics panel. Service mode and codes will appear in display area. Current Code 51 (accident detected) cannot be cleared using on-board diagnostics; a scan tester is necessary to clear current Code 51. Current Code 34 will remain current after fault is repaired unless ignition is off long enough to allow 36-Volt Loop Reserve (36VLR) to fully discharge.

Note. Failure to follow diagnostic procedures may result in extended diagnostic time and incorrect diagnosis and parts replacement.

Diagnostic Procedure

1. SIR SYSTEM DIAGNOSTIC CHECK should always be starting point of SIR diagnostics. See appropriate SIR DIAGNOSTIC SYSTEM CHECK under DIAGNOSTIC CHARTS. SIR DIAGNOSTIC SYSTEM CHECK checks for proper INFLATABLE RESTRAINT indicator light operation and SIR trouble codes using flash code and scan tester methods.
2. SIR DIAGNOSTIC SYSTEM CHECK will lead to correct diagnostic chart to diagnose SIR problems. Always perform SIR DIAGNOSTIC SYSTEM CHECK after repair or diagnostic procedures to ensure repair is correct and no other problems are present.

Description

Diagnostic procedures used in this section are designed to find and repair SIR problems. For best results, utilize diagnostic charts and follow sequence listed below

1. Perform SIR DIAGNOSTIC SYSTEM CHECK. SIR DIAGNOSTIC SYSTEM CHECK should be start of any SIR diagnosis. SIR DIAGNOSTIC SYSTEM CHECK checks for proper AIR BAG/INFLATABLE RESTRAINT indicator operation and SIR trouble codes.
2. Refer to diagnostic chart as directed by SIR DIAGNOSTIC SYSTEM CHECK. SIR DIAGNOSTIC SYSTEM CHECK will lead to correct chart to diagnose any SIR problems. By-passing these procedures may result in extended diagnostic time, incorrect diagnosis, and incorrect parts replacement.
3. Repeat SIR DIAGNOSTIC SYSTEM CHECK after any repair or diagnostic procedures are performed. Repeating SIR DIAGNOSTIC SYSTEM CHECK will ensure repair was made correctly and no other conditions exist. When ignition is first turned on, system voltage is applied through AIRBAG#1C fuse to Sensing and Diagnostic Module (SDM) at IGNITION 1 input terminal B9 and from CHIME/CLSTR/RAC/MISC/#1D fuse to SDM at REDUNDANT INDICATOR IGNITION 1 input terminal A4. SDM responds by flashing AIR BAG indicator 7 times. When engine is cranked, system voltage is applied from AIRBAG/VATS#1A fuse to SDM at CRANK input terminal B1. SDM grounds light circuit until system voltage is removed from CRANK input. This results in a steady AIR BAG indicator during cranking. After engine is cranked, SDM will flash AIR BAG indicator 6 times.

Note. Test numbers refer to test numbers on diagnostic chart. For circuit number identification, see WIRING DIAGRAMS.

1. AIR BAG indicator should flash 7 times after ignition is first turned on.
2. AIR BAG indicator should remain on steady during cranking.
3. After cranking, AIR BAG indicator should flash 6 times and go off.
4. Checks for proper operation of SERIAL DATA circuit. This test will also determine which history codes, if any, are stored.
5. Indicates a malfunction in redundant light driver circuit when AIR BAG warning light flashes 4 times during BULB CHECK. These malfunctions are diagnosed by DTC 62 chart.
6. Indicates improper operation of AIR BAG warning light. Differentiates a "warning light stays on" condition from a "warning light does not come on" condition.
7. Checks for proper operation of SERIAL DATA circuit. Will also identify stored DTCs and whether they are current or history.

Diagnostic Aids

Order in which DTCs are diagnosed is very important. Failure to diagnose DTCs in order specified may result in extended diagnostic time, incorrect diagnosis, and incorrect parts replacement.

Scheme 5

When SDM recognizes IGNITION 1 voltage applied to terminal B9 is greater than 6.4 volts, the AIR BAG warning light is flashed 7 times to verify operation. At this time SDM performs TURN-ON tests followed by CURRENT SOURCE DIAGNOSTICS and CONTINUOUS MONITORING tests. When a malfunction is detected, SDM sets a current DTC and illuminates AIR BAG warning light. SDM will clear current DTCs and move them to a history file when malfunction is no longer detected and/or ignition switch is cycled, except for DTCs 51, 52, and 71. DTC 51 can only be cleared using a scan tool CLEAR CODES command. DTCs 52 and 71 may not clear after a CLEAR CODES command is issued.

Note. Test numbers refer to test numbers on diagnostic chart. For circuit number identification, see WIRING DIAGRAMS.

1. Test confirms a current malfunction. If no current malfunction is occurring (history DTC set), DIAGNOSTIC AIDS for appropriate DTC should be referenced. SDM should not be replaced for a history DTC.
2. Checks for a malfunction introduced into SIR system during diagnostic process. It is unlikely that a malfunctioning SDM would cause a new malfunction to occur during diagnostic process.
3. When all circuits outside SDM has been found to operate correctly, as indicated by appropriate diagnostic chart, then and only then should SDM be replaced.

Scheme 6

When ignition is first turned on, system voltage is applied from CHIME/CLSTR/RAC/MISC#1D fuse to REDUNDANT INDICATOR IGNITION 1, terminal A4, and to AIR BAG indicator light, which is connected to SIR INDICATOR terminal A9. AIRBAG#1C fuse applies system voltage to IGNITION 1 input, terminal B9. SDM responds by flashing AIR BAG warning light 7 times. If IGNITION 1 is outside of normal operating voltage range, AIR BAG warning light will come on with no DTCs set. When engine is being cranked, IGNITION 1 voltage is applied from AIRBAG/VATS#1A fuse to SDM at CRANK input. SDM responds by grounding SIR INDICATOR output until IGNITION 1 voltage is removed from CRANK input. This results in AIR BAG warning light being on during cranking. After engine is cranked, SDM will flash AIR BAG indicator 6 times.

Note. Test numbers refer to test numbers on diagnostic chart. For circuit number identification, see WIRING DIAGRAMS.

1. An open AIRBAG#1C fuse would cause AIR BAG light to come on steady.
2. Disconnected SDM harness connector will cause warning light to come on steady via shorting bar from terminal A9 to terminal A10 (ground).
3. Checks for an open in ground circuit to SDM.
4. Checks for an open in IGNITION 1 circuit to SDM.
5. Checks for a short from CRANK input on SDM to voltage.
6. Checks for a short from SIR INDICATOR circuit to ground. WARNING: To avoid air bag deployment and injury when trouble shooting system, only use test equipment specified in diagnostic charts. Under no circumstances should battery powered test equipment or test light be used. Carefully follow all instructions.
7. Checks whether a short to ground caused AIRBAG#1C fuse to open.
8. Determines whether short to ground is due to a short in wiring.

Scheme 7

When ignition is first turned on, system voltage is applied from CHIME/CLSTR/RAC/MISC#1D fuse to REDUNDANT INDICATOR IGNITION 1, terminal A4, and to AIR BAG indicator light, which is connected to SIR INDICATOR, terminal A9. AIRBAG#1C fuse applies system voltage to IGNITION 1 input, terminal B9. SDM responds by flashing AIR BAG warning light 7 times. If IGNITION 1 is outside of normal operating voltage range, AIR BAG warning light will come on with no DTCs set. When engine is being cranked, IGNITION 1 voltage is applied from AIRBAG/VATS#1A fuse to SDM at CRANK input. SDM responds by grounding SIR INDICATOR output until IGNITION 1 voltage is removed from CRANK input. This results in AIR BAG warning light being on during cranking. After engine is cranked, SDM will flash AIR BAG indicator 6 times.

Note. Test numbers refer to test numbers on diagnostic chart. For circuit number identification, see WIRING DIAGRAMS.

1. Checks whether malfunction is in AIR BAG warning light circuit or in instrument cluster power feed circuit.
2. Checks for an open in REDUNDANT INDICATOR IGNITION 1 circuit.
3. Checks for an open in SIR INDICATOR circuit, instrument cluster circuit or instrument cluster power feed circuit.
4. Checks whether open is caused by a bad bulb.
5. Checks whether malfunction is an open in SIR INDICATOR circuit or an open in instrument cluster.
6. Checks whether malfunction is due to a short from SIR INDICATOR circuit to voltage.

Scheme 8

When ignition is first turned on, system voltage is applied from CHIME/CLSTR/RAC/MISC#1D fuse to REDUNDANT INDICATOR IGNITION 1, terminal A4, and to AIR BAG indicator light, which is connected to SIR INDICATOR, terminal A9. AIRBAG#1C fuse applies system voltage to IGNITION 1 input, terminal B9. SDM responds by flashing AIR BAG warning light 7 times. If IGNITION 1 is outside of normal operating voltage range, AIR BAG warning light will come on with no DTCs set. When engine is being cranked, IGNITION 1 voltage is applied from AIRBAG/VATS#1A fuse to SDM at CRANK input. SDM responds by grounding SIR INDICATOR output until IGNITION 1 voltage is removed from CRANK input. This results in AIR BAG warning light being on during cranking. After engine is cranked, SDM will flash AIR BAG indicator 6 times.

Note. Test numbers refer to test numbers on diagnostic chart. For circuit number identification, see WIRING DIAGRAMS.

1. Checks whether malfunction is in AIR BAG warning light circuit or in instrument cluster power feed circuit.
2. Checks for an open in REDUNDANT INDICATOR IGNITION 1 circuit.
3. Checks for an open in SIR INDICATOR circuit, instrument cluster circuit or instrument cluster power feed circuit.
4. Checks whether open is caused by a bad bulb.
5. Checks whether malfunction is an open in SIR INDICATOR circuit or an open in instrument cluster.
6. Checks whether malfunction is due to a short from SIR INDICATOR circuit to voltage.

Scheme 9

When ignition is first turned on, system voltage is applied from CHIME/CLSTR/RAC/MISC#1D fuse to REDUNDANT INDICATOR IGNITION 1, terminal A4, and to AIR BAG indicator light, which is connected to SIR INDICATOR, terminal A9. AIRBAG#1C fuse applies system voltage to IGNITION 1 input, terminal B9. SDM responds by flashing AIR BAG warning light 7 times. If IGNITION 1 is outside of normal operating voltage range, AIR BAG warning light will come on with no DTCs set. When engine is being cranked, IGNITION 1 voltage is applied from AIRBAG/VATS#1A fuse to SDM at CRANK input. SDM responds by grounding SIR INDICATOR output until IGNITION 1 voltage is removed from CRANK input. This results in AIR BAG warning light being on during cranking. After engine is cranked, SDM will flash AIR BAG indicator 6 times.

Note. Test numbers refer to test numbers on diagnostic chart. For circuit number identification, see WIRING DIAGRAMS.

1. Checks whether malfunction is in AIR BAG warning light circuit or in instrument cluster power feed circuit.
2. Checks for an open in REDUNDANT INDICATOR IGNITION 1 circuit.
3. Checks for an open in SIR INDICATOR circuit, instrument cluster circuit or instrument cluster power feed circuit.
4. Checks whether open is caused by a bad bulb.
5. Checks whether malfunction is an open in SIR INDICATOR circuit or an open in instrument cluster.
6. Checks whether malfunction is due to a short from SIR INDICATOR circuit to voltage.

Scheme 10

When ignition is first turned on, system voltage is applied from CHIME/CLSTR/RAC/MISC#1D fuse to REDUNDANT INDICATOR IGNITION 1, terminal A4, and to AIR BAG indicator light, which is connected to SIR INDICATOR, terminal A9. AIRBAG#1C fuse applies system voltage to IGNITION 1 input, terminal B9. SDM responds by flashing AIR BAG warning light 7 times. If IGNITION 1 is outside of normal operating voltage range, AIR BAG warning light will come on with no DTCs set. When engine is being cranked, IGNITION 1 voltage is applied from AIRBAG/VATS#1A fuse to SDM at CRANK input. SDM responds by grounding SIR INDICATOR output until IGNITION 1 voltage is removed from CRANK input. This results in AIR BAG warning light being on during cranking. After engine is cranked, SDM will flash AIR BAG indicator 6 times.

Note. Test numbers refer to test numbers on diagnostic chart. For circuit number identification, see WIRING DIAGRAMS.

1. Checks whether malfunction is in AIR BAG warning light circuit or in instrument cluster power feed circuit.
2. Checks for an open in REDUNDANT INDICATOR IGNITION 1 circuit.
3. Checks for an open in SIR INDICATOR circuit, instrument cluster circuit or instrument cluster power feed circuit.
4. Checks whether open is caused by a bad bulb.
5. Checks whether malfunction is an open in SIR INDICATOR circuit or an open in instrument cluster.
6. Checks whether malfunction is due to a short from SIR INDICATOR circuit to voltage.

Scheme 11

CHART C - AIR BAG WARNING LAMP DOES NOT COME ON (LESABRE WITH STANDARD INSTRUMENTATION)

Note. Test numbers refer to test numbers on diagnostic chart. For circuit number identification, see WIRING DIAGRAMS.

1. Checks whether power is available to instrument cluster power feed circuit.
2. Checks for a short from instrument cluster power feed circuit to ground.
3. Checks whether short to ground is due to a short in wiring.
4. Checks whether malfunction is due to an open power feed circuit from CHIME/CLSTR/RAC/MISC#1D fuse to connector C200 terminal D9.
5. Determines whether malfunction is due to an open power feed circuit from connector C200 terminal D9, to instrument cluster or an open in power feed to CHIME/CLSTR/RAC/MISC#1D fuse.

Scheme 12

CHART C - AIR BAG WARNING LAMP DOES NOT COME ON (LESABRE WITH OPTIONAL ANALOG INSTRUMENTATION)

Note. Test numbers refer to test numbers on diagnostic chart. For circuit number identification, see WIRING DIAGRAMS.

1. Checks whether power is available to information center power feed circuit.
2. Checks for a short from information center power feed circuit to ground.
3. Checks whether short to ground is due to a short in wiring.
4. Checks whether malfunction is due to an open power feed circuit from CHIME/CLSTR/RAC/MISC#1D fuse to information center harness connector terminal B6 or power feed to CHIME/CLSTR/RAC/MISC#1D fuse.

Scheme 13

CHART C - AIR BAG WARNING LAMP DOES NOT COME ON (EIGHTY EIGHT)

Note. Test numbers refer to test numbers on diagnostic chart. For circuit number identification, see WIRING DIAGRAMS.

1. Checks whether power is available to instrument cluster power feed circuit.
2. Checks for a short from instrument cluster power feed circuit to ground.
3. Checks whether short to ground is due to a short in wiring.
4. Checks whether malfunction is due to an open power feed circuit from CHIME/CLSTR/RAC/MISC#1D fuse to instrument cluster harness connector or power feed to CHIME/CLSTR/RAC/MISC#1D fuse.

Scheme 14

CHART C - AIR BAG WARNING LAMP DOES NOT COME ON (BONNEVILLE)

Note. Test numbers refer to test numbers on diagnostic chart. For circuit number identification, see WIRING DIAGRAMS.

1. Checks whether power is available to instrument cluster power feed circuit.
2. Checks for a short from instrument cluster power feed circuit to ground.
3. Checks whether short to ground is due to a short in wiring.
4. Checks whether malfunction is due to an open power feed circuit from CHIME/CLSTR/RAC/MISC#1D fuse to instrument cluster harness connector C200 terminal D9.
5. Checks whether malfunction is due to an open power feed circuit from connector C200 terminal D9 to instrument cluster, or an open in power feed circuit to CHIME/CLSTR/RAC/MISC#1D fuse.

Scheme 15

When ignition is first turned on, system voltage is applied from CHIME/CLSTR/RAC/MISC#1D fuse to REDUNDANT INDICATOR IGNITION 1, terminal A4, and to AIR BAG indicator light, which is connected to SIR INDICATOR, terminal A9. AIRBAG#1C fuse applies system voltage to IGNITION 1 input, terminal B9. SDM responds by flashing AIR BAG warning light 7 times. If IGNITION 1 is outside of normal operating voltage range, AIR BAG warning light will come on with no DTCs set. When engine is being cranked, IGNITION 1 voltage is applied from AIRBAG/VATS#1A fuse to SDM at CRANK input. SDM responds by grounding SIR INDICATOR output until IGNITION 1 voltage is removed from CRANK input. This results in AIR BAG warning light being on during cranking. After engine is cranked, SDM will flash AIR BAG indicator 6 times.

Note. Test numbers refer to test numbers on diagnostic chart. For circuit number identification, see WIRING DIAGRAMS.

1. Checks whether fault is due to an open AIRBAG/VATS#1A fuse.
2. Checks for a proper signal to CRANK input during cranking.
3. Determines whether lack of proper crank signal is due to an open CRANK input circuit or an open power feed to AIRBAG/VATS#1A fuse.
4. Checks whether AIRBAG/VATS#1A fuse is open due to a short to ground in CRANK input circuit.
5. Checks whether short to ground is in wiring harness.

Scheme 16

When ignition is first turned on, system voltage is applied from CHIME/CLSTR/RAC/MISC#1D fuse to REDUNDANT INDICATOR IGNITION 1, terminal A4, and to AIR BAG indicator light, which is connected to SIR INDICATOR, terminal A9. AIRBAG#1C fuse applies system voltage to IGNITION 1 input, terminal B9. SDM responds by flashing AIR BAG warning light 7 times. If IGNITION 1 is outside of normal operating voltage range, AIR BAG warning light will come on with no DTCs set. When engine is being cranked, IGNITION 1 voltage is applied from AIRBAG/VATS#1A fuse to SDM at CRANK input. SDM responds by grounding SIR INDICATOR output until IGNITION 1 voltage is removed from CRANK input. This results in AIR BAG warning light being on during cranking. After engine is cranked, SDM will flash AIR BAG indicator 6 times.

Failure Conditions

DTC will set when combined resistance of passenger inflator module, harness wiring at circuit No. 1403 and 1404, and connector terminal contact is greater than a specified value.

Action Taken

SDM turns on AIR BAG warning light and sets DTC.

Note. Test numbers refer to test numbers on diagnostic chart. For circuit number identification, see WIRING DIAGRAMS.

1. Determines whether malfunction is in passenger inflator module circuit or in SDM wiring harness circuit.
2. Checks whether malfunction is caused by high resistance in circuit No. 1403.
3. Checks whether malfunction is caused by high resistance in circuit No. 1404.

An intermittent condition is likely to be caused by a poor connection at passenger inflator module harness connector terminals "A" and "B", SDM terminals A5 and A6, or a poor connection in circuit No. 1403 or 1404. Test for this DTC is only run while AIR BAG warning light is performing bulb check, unless DTC 17 or 26 is detected. When a scan tool CLEAR CODES command is issued and malfunction is still present, DTC will not reappear until next ignition cycle.

Scheme 17

When ignition switch is turned on, SDM performs tests to diagnose critical malfunctions within itself. Upon passing these tests, IGNITION 1, 36VLR, and deployment loop voltages are measured to ensure they are within their respective normal voltages ranges. SDM then proceeds with CURRENT SOURCE DIAGNOSTICS. PASSENGER-SIDE LOW terminal A5 is grounded through a resistor and passenger current source connected to PASSENGER-SIDE HIGH terminal A6 allows a known amount of current to flow. By monitoring voltage difference between PASSENGER-SIDE HIGH and PASSENGER-SIDE LOW, the SDM calculates combined resistance of passenger inflator module, harness wiring at circuit No. 1403 and 1404, and connector terminal contact.

DTC will set when combined resistance of passenger inflator module, harness wiring at circuit No. 1403 and 1404, and connector terminal contact is less than a specified value.

SDM turns on AIR BAG warning light and sets DTC.

Note. Test numbers refer to test numbers on diagnostic chart. For circuit number identification, see WIRING DIAGRAMS.

1. DTC 16 and 22 will set simultaneously when DRIVER-SIDE HIGH circuit is shorted to PASSENGER-SIDE HIGH circuit due to parallel current paths.
2. Test determines whether malfunction is in passenger inflator module circuit or in SDM wiring harness circuit.
3. Checks for a short from PASSENGER-SIDE HIGH circuit to PASSENGER-SIDE LOW circuit.
4. Checks for a short from PASSENGER-SIDE HIGH circuit to DRIVER-SIDE LOW circuit.

An intermittent condition is likely to be caused by a short between circuit No. 1403 and circuit No. 347, 348, or 1404, or a malfunctioning shorting bar on passenger inflator module which would require replacement of module. Test for this DTC is only run while AIR BAG warning light is performing bulb check, unless DTCs 17 or 26 are detected. When a scan tool CLEAR CODES command is issued and malfunction is still present, DTC will not reappear until next ignition cycle.

Scheme 18

When ignition switch is turned on, SDM performs tests to diagnose critical malfunctions within itself. Upon passing these tests, IGNITION 1, 36VLR, and deployment loop voltages are measured to ensure they are within their respective normal voltage ranges. SDM then proceeds with CURRENT SOURCE DIAGNOSTICS. PASSENGER-SIDE LOW terminal A5 is grounded through a resistor and passenger current source connected to PASSENGER-SIDE HIGH terminal A6 allows a known amount of current to flow. After CURRENT SOURCE DIAGNOSTICS are completed SDM removes low resistance ground from PASSENGER-SIDE LOW and switches passenger current source at PASSENGER-SIDE HIGH. SDM then measures voltage at PASSENGER-SIDE HIGH and PASSENGER-SIDE LOW during CONTINUOUS MONITORING. By monitoring voltage difference between PASSENGER-SIDE HIGH and PASSENGER-SIDE LOW, SDM calculates combined resistance of passenger inflator module, wiring in circuit No. 1403 and 1404, and connector terminal contact.

Code sets if voltage difference between PASSENGER-SIDE HIGH terminal A6 and PASSENGER-SIDE LOW terminal A5 is above or equal to a specified value for 500 milliseconds during CURRENT SOURCE DIAGNOSIS or CONTINUOUS MONITORING.

SDM turns on AIR BAG warning light and sets a DTC.

Note. Test numbers refer to test numbers on diagnostic chart. For circuit number identification, see WIRING DIAGRAMS.

1. Test determines whether malfunction is in passenger inflator module circuit or SDM wiring harness circuit.
2. Checks whether malfunction is caused by high resistance in circuit No. 1403.
3. Checks whether malfunction is caused by high resistance in circuit No. 1404.

An intermittent condition is likely to be caused by a poor connection at passenger inflator module harness connector terminals "A" and "B", SDM terminals "A5" and "A6", or an open in circuit No. 1403 or 1404.

Scheme 19

When ignition switch is turned on, SDM performs tests to diagnose critical malfunctions within itself. Upon passing these tests, IGNITION 1, 36VLR, and deployment loop voltages are measured to ensure they are within their respective normal voltage ranges. SDM then proceeds with CURRENT SOURCE DIAGNOSTICS. DRIVER-SIDE LOW terminal A2 is grounded through a resistor and driver current source connected to DRIVER-SIDE HIGH terminal A1 allows a known amount of current to flow. By monitoring voltage difference between DRIVER-SIDE HIGH and DRIVER-SIDE LOW, SDM calculates combined resistance of driver inflator module, SIR coil assembly, wiring in circuit No. 347 and 348, and connector terminal contact.

Code sets if combined resistance of driver inflator module, SIR coil assembly, harness wiring at circuit No. 347 and 348, and connector terminal contact is greater than a specified value.

SDM turns on AIR BAG warning light and sets a DTC.

Note. Test numbers refer to test numbers on diagnostic chart. For circuit number identification, see WIRING DIAGRAMS.

1. Determines whether malfunction is in driver inflator module circuit or in SDM wiring harness circuit.
2. Checks whether malfunction is caused by high resistance in circuit No. 347.
3. Checks whether malfunction is caused by high resistance in circuit No. 348.
4. Checks whether malfunction is in driver inflator module or SIR coil assembly.

Scheme 20

When ignition switch is turned on, SDM performs tests to diagnose critical malfunctions within itself. Upon passing these tests, IGNITION 1, 36VLR, and deployment loop voltages are measured to ensure they are within their respective normal voltage ranges. SDM then proceeds with CURRENT SOURCE DIAGNOSTICS. DRIVER-SIDE LOW terminal A2 is grounded through a resistor and driver current source connected to DRIVER-SIDE HIGH terminal A1 allows a known amount of current to flow. By monitoring voltage difference between DRIVER-SIDE HIGH and DRIVER-SIDE LOW, SDM calculates combined resistance of driver inflator module, SIR coil assembly, wiring in circuit No. 347 and 348, and connector terminal contact.

Code sets if combined resistance of driver inflator module, SIR coil assembly, harness wiring at circuit No. 347 and 348, and connector terminal contact is greater than a specified value.

SDM turns on AIR BAG warning light and sets a DTC.

Note. Test numbers refer to test numbers on diagnostic chart. For circuit number identification, see WIRING DIAGRAMS.

1. DTC 16 and 22 will set simultaneously when DRIVER-SIDE HIGH circuit is shorted to PASSENGER-SIDE HIGH circuit due to parallel current paths.
2. Checks whether malfunction is in driver inflator module circuit or in SDM wiring harness circuit.
3. Checks for a short from DRIVER-SIDE HIGH circuit to DRIVER-SIDE LOW circuit.
4. Checks for a short from DRIVER-SIDE HIGH circuit to PASSENGER-SIDE LOW circuit.
5. Checks whether malfunction is in driver inflator module or SIR coil assembly.

An intermittent condition is likely to be caused by a short between circuit No. 347 and circuit No. 348, 1403, or 1404, or a malfunctioning shorting bar on driver inflator module or SIR coil assembly which would require replacement of component. Test for this DTC is only run while AIR BAG warning light is performing bulb check, unless DTC 17 or DTC 26 is detected. When a scan tool CLEAR CODES command is issued and malfunction is still present, DTC will not reappear until next ignition cycle.

Scheme 21

When ignition switch is turned on, SDM performs tests to diagnose critical malfunctions within itself. Upon passing these tests, IGNITION 1, 36VLR, and deployment loop voltages are measured to ensure they are within their respective normal voltage ranges. SDM then monitors voltages at DRIVER-SIDE LOW terminal A2 and PASSENGER-SIDE LOW terminal A5 to detect shorts to ground in inflator module circuit.

Code sets if 36VLR power supply in SDM is in normal operating range and at least one of 2 inflator modules is not open.

SDM turns on AIR BAG warning light and sets a DTC.

Note. Test numbers refer to test numbers on diagnostic chart. For circuit number identification, see WIRING DIAGRAMS.

Scheme 22

1. Checks whether malfunction is occurring in driver inflator module circuit.
2. Checks whether malfunction is occurring in passenger inflator module circuit. WARNING: To avoid air bag deployment and injury when trouble shooting system, only use test equipment specified in diagnostic charts. Under no circumstances should battery powered test equipment or test light be used. Carefully follow all instructions.
3. Checks for a short from DRIVER-SIDE HIGH to ground.
4. Checks for a short from DRIVER-SIDE LOW to ground.
5. Checks for a short from PASSENGER-SIDE LOW to ground.
6. Checks for a short from PASSENGER-SIDE HIGH to ground.

An intermittent condition is likely to be caused by a short to ground in inflator module circuits. Check circuit No. 347, 348, 1403, and 1404 carefully. If wiring pigtail of SIR coil assembly, driver inflator module, or passenger inflator module is damaged, component must be replaced.

Scheme 23

DTC 25 - INITIATOR CIRCUIT SHORT TO IGNITION

Note. When DTC 25 has been set, it is necessary to replace SDM. Setting DTC 25 will also cause DTC 71 to set. When a scan tool CLEAR CODES command is issued and malfunction is still present, DTC 25 and 71 will remain current. When a scan tool CLEAR CODES command is issued and malfunction is no longer present, DTC 25 will clear, but DTC 71 will remain current. Ensure short to voltage condition is repaired before installing a replacement SDM to avoid damaging SDM.

When ignition switch is turned on, SDM performs tests to diagnose critical malfunctions within itself. Upon passing these tests, IGNITION 1, 36VLR, and deployment loop voltages are measured to ensure they are within their respective normal voltage ranges. SDM then monitors voltages at DRIVER-SIDE LOW terminal A2 and PASSENGER-SIDE LOW terminal A5 to detect shorts to voltage in inflator module circuits.

Code sets if 36VLR power supply in SDM is in normal operating voltage range and neither of 2 inflator modules is open.

SDM turns on AIR BAG warning light and sets a DTC.

Note. Test numbers refer to test numbers on diagnostic chart. For circuit number identification, see WIRING DIAGRAMS.

Scheme 24

1. Checks whether malfunction is occurring in driver inflator module circuit.
2. Checks whether malfunction is occurring in passenger inflator module circuit. WARNING: To avoid air bag deployment and injury when trouble shooting system, only use test equipment specified in diagnostic charts. Under no circumstances should battery powered test equipment or test light be used. Carefully follow all instructions.
3. Checks for a short from DRIVER-SIDE HIGH to voltage.
4. Checks for a short from DRIVER-SIDE LOW to voltage.
5. Checks for a short from PASSENGER-SIDE HIGH to voltage.
6. Checks for a short from PASSENGER-SIDE LOW to voltage.

An intermittent condition is likely to be caused by a short to voltage in inflator module circuits. A history DTC 25 would be accompanied by a current DTC 71. A careful inspection of circuits and components indicated on DTC 25 charts is essential to ensure that replacement SDM will not be damaged.

Scheme 25

When ignition switch is turned on, SDM performs tests to diagnose critical malfunctions within itself. Upon passing these tests, IGNITION 1, 36VLR, and deployment loop voltages are measured to ensure they are within their respective normal voltage ranges. SDM then proceeds with CURRENT SOURCE DIAGNOSIS. DRIVER-SIDE LOW terminal A2 is grounded through a resistor and driver current source connected to DRIVER-SIDE HIGH terminal A1 allows a known amount of current to flow. After CURRENT SOURCE DIAGNOSTICS are completed, SDM removes low resistance ground from DRIVER-SIDE LOW and switches driver current source at DRIVER-SIDE HIGH. SDM then monitors voltages at DRIVER-SIDE HIGH and DRIVER-SIDE LOW during CONTINUOUS MONITORING.

Code sets if voltage difference between DRIVER-SIDE HIGH terminal A1 and DRIVER-SIDE LOW terminal A2 is greater than or equal to a specified value for 500 milliseconds during CURRENT SOURCE DIAGNOSIS or CONTINUOUS MONITORING.

SDM turns on AIR BAG warning light and sets a DTC.

Note. Test numbers refer to test numbers on diagnostic chart. For circuit number identification, see WIRING DIAGRAMS.

1. Test determines whether malfunction is in driver inflator module circuit or in SDM wiring harness circuit.
2. Checks whether malfunction is due to high resistance in circuit No. 347.
3. Checks whether malfunction is due to high resistance in circuit No. 348.
4. Checks whether malfunction is in driver inflator module or SIR coil assembly.

An intermittent condition is likely to be caused by a poor connection at driver inflator module terminals "A" and "B", SDM terminals A1 and A2, or an open in circuit No. 347 and 348.

Scheme 26

When ignition switch is turned on, SDM performs tests to diagnose critical malfunctions within itself. Upon passing these tests, IGNITION 1, 36VLR, and deployment loop voltages are measured to ensure they are within their respective normal voltage ranges. SDM then proceeds with CURRENT SOURCE DIAGNOSTICS, followed by CONTINUOUS MONITORING. SDM supplies REFERENCE VOLTAGE at terminal B6 and measures voltage at SENSOR SIGNAL terminal B5. During normal operation voltage measured at SENSOR SIGNAL will be about one-half REFERENCE VOLTAGE.

Code sets when voltage measured at SENSOR SIGNAL terminal B5 is less than a specified value for 500 milliseconds during CONTINUOUS MONITORING.

SDM turns on AIR BAG warning light and sets a DTC.

Note. Test numbers refer to test numbers on diagnostic chart. For circuit number identification, see WIRING DIAGRAMS.

1. Checks proper resistance of forward discriminating sensor.
2. Checks for an open in REFERENCE VOLTAGE circuit.
3. Checks for an open in SENSOR SIGNAL circuit.
4. Checks for a short from REFERENCE VOLTAGE to ground.
5. Checks for a short from SENSOR SIGNAL to ground.

An intermittent condition is likely to be caused by a poor connection to forward discriminating sensor at terminals "A" or "B", poor connection to SDM at terminals B5 or B6, a short to ground in circuit No. 1751 or 1834, or an open in circuit No. 1751 or 1834.

Scheme 27

When ignition switch is turned on, SDM performs tests to diagnose critical malfunctions within itself. Upon passing these tests, IGNITION 1, 36VLR, and deployment loop voltages are measured to ensure they are within their respective normal voltage ranges. SDM then proceeds with CURRENT SOURCE DIAGNOSTICS, followed by CONTINUOUS MONITORING. SDM supplies REFERENCE VOLTAGE at terminal B6 and measures voltage at SENSOR SIGNAL terminal B5. During normal operation voltage measured at SENSOR SIGNAL will be about one-half REFERENCE VOLTAGE.

Code sets when voltage measured at SENSOR SIGNAL terminal B5 is greater than a specified value for 500 milliseconds during CONTINUOUS MONITORING.

SDM turns on AIR BAG warning light and sets a DTC.

Note. Test numbers refer to test numbers on diagnostic chart. For circuit number identification, see WIRING DIAGRAMS.

1. Checks proper resistance of forward discriminating sensor.
2. Checks for a short in REFERENCE VOLTAGE circuit to SENSOR SIGNAL circuit.
3. Checks for a short from REFERENCE VOLTAGE to voltage.
4. Checks for a short from SENSOR SIGNAL to voltage.

An intermittent condition is likely to be caused by a short from circuit No. 1751 to 1834 or a short to voltage from circuit No. 1751 or 1834.

Scheme 28

SDM contains a sensing device which converts vehicle velocity changes into an electrical signal. Electrical signal generated is processed by SDM and then compared to a value stored in memory. When generated signal exceeds stored value, additional signal processing is performed and generated signals are compared to signals stored in memory. When 2 generated signals exceed stored values or when one generated signal exceeds stored value and forward discriminating sensor closes, SDM will cause current to flow through inflator modules, deploying air bags and causing DTC 51 to set.

Code sets when SDM senses a frontal crash (up to 30 degrees off centerline of vehicle) of sufficient force to warrant deployment of air bags.

SDM turns on AIR BAG warning light, records crash data, and sets a DTC.

Note. Test numbers refer to test numbers on diagnostic chart. For circuit number identification, see WIRING DIAGRAMS.

1. If inflator module(s) has not deployed, DTC 51 may have set falsely.
2. If DTC 51 has set with no signs of frontal impact, DTC has set falsely.
3. Checks for an SDM malfunction setting DTC.
4. Determines whether DTC was set inadvertently during diagnosis.
5. When a frontal crash has occurred, it is necessary to perform indicated procedures to ensure SIR system is fully functional.

Scheme 29

When there is a frontal crash of sufficient force (up to 30 degrees off centerline of vehicle) SDM will cause enough current to flow to deploy air bags and will set DTC 51. At this time SDM will record information regarding SIR system status and vehicle status in EEPROM. DTC 52 will set when SDM has stored information regarding 2 frontal crash events.

SDM attempts to store frontal crash information and finds EEPROM data area full. Test is run each time SDM stores or attempts to store information regarding a frontal crash event and also during TURN-ON tests.

SDM turns on AIR BAG warning light and sets a DTC.

Scheme 30

When ignition switch is first turned on, battery voltage is applied to AIR BAG warning light and to IGNITION 1 input terminal B9. SDM responds by flashing AIR BAG warning light 7 times alternating between primary and redundant lamp drivers. SDM monitors primary lamp driver output by comparing output state at SIR INDICATOR terminal A9 to microprocessor commanded state. When IGNITION 1 is greater than a specified value, and output state does not match commanded state of primary lamp driver for 400 milliseconds DTC 61 is set.

DTC will set when IGNITION 1 voltage is greater than a specified value and output state at SIR INDICATOR terminal A9 does not match commanded state of primary lamp driver for 400 milliseconds. This test is run every 100 milliseconds during CONTINUOUS MONITORING.

SDM attempts to turn on AIR BAG warning light using redundant lamp driver and sets a DTC.

Note. Test numbers refer to test numbers on diagnostic chart. For circuit number identification, see WIRING DIAGRAMS.

1. When SDM is configured for a serial data controlled warning light, DTC 61 will set. Clearing SIR diagnostic trouble codes will reset SDM allowing SDM to control AIR BAG warning light.

Refer to CHARTS B and C to diagnose warning lamp circuit malfunctions.

Scheme 31

When ignition switch is first turned on, battery voltage is applied to AIR BAG warning light and to IGNITION 1 input terminal B9. SDM responds by flashing AIR BAG warning light 7 times alternating between primary and redundant lamp drivers. SDM monitors redundant lamp driver output by comparing output state at SIR INDICATOR terminal A9 to microprocessor commanded state. When IGNITION 1 is greater than a specified value and output state does not match commanded state of redundant lamp driver for 400 milliseconds DTC 62 is set.

DTC will set when IGNITION 1 voltage is greater than a specified value and output state at SIR INDICATOR terminal A9 does not match commanded state of redundant lamp driver for 400 milliseconds. This test is run every 100 milliseconds during CONTINUOUS MONITORING.

SDM attempts to turn on AIR BAG warning light using primary lamp driver and sets a DTC.

Note. Test numbers refer to test numbers on diagnostic chart. For circuit number identification, see WIRING DIAGRAMS.

1. Test determines whether malfunction is due to an open in REDUNDANT INDICATOR IGNITION 1 circuit.

An intermittent condition is likely to be caused by a poor connection to SDM at terminal A4 or an open in circuit No. 39B. A poor REDUNDANT INDICATOR GROUND connection to SDM would set DTC 62. It is important that SDM mounting surface is free of any dirt or foreign material and that fasteners are properly torqued to ensure a good REDUNDANT INDICATOR GROUND.

Scheme 32

DTC 71 - INTERNAL SDM FAULT

Note. When DTC 25 has been set it is necessary to replace SDM. Setting DTC 25 will also cause DTC 71 to set. When a scan tool CLEAR CODES command is issued and malfunction is still present, DTCs 25 and 71 will remain current. When a scan tool CLEAR CODES command is issued and malfunction is no longer present, DTC 25 will clear but DTC 71 will remain current. Ensure that short to voltage condition is repaired prior to installing a replacement SDM to avoid damaging SDM.

DTC 71 is an indication of a potential internal SDM malfunction and will set if: 1) 36VLR voltage is out of normal operating range; 2) crash data recording reserve voltage discharge time fails for 3 consecutive ignition cycles; 3) calculated check sum for internal memory does not match stored value or voltage measured at DRIVER-SIDE LOW and/or PASSENGER-SIDE LOW is too high; 4) sensing device inside SDM that converts vehicle velocity changes to an electrical signal malfunctioning; 5) driver current source and/or passenger current source is malfunctioning; 6) temporary memory storage area is malfunctioning; 7) SDM is unable to read from or write to EEPROM; 8) arming sensor inside SDM is not closed during a deployment event; 9) DTC 25 has been set.

DTC 71 will set when malfunctions in TURN-ON, CONTINUOUS MONITORING and/or CURRENT SOURCE DIAGNOSTICS are detected by SDM.

SDM turns on AIR BAG warning light and sets a DTC.

Scheme 33

WIRE REPAIR

Because of sensitive nature of circuitry, manufacturer has developed special wiring repair procedures. Wire Repair Kit (J-38125-A) contains special sealed splices for use in repairing SIR wiring. Sealed splices are a heat shrink sleeve with sealing adhesive to produce a sealed splice and a cross-hatched core crimp to produce a positive contact for low energy circuits.

If any terminal or connector in SIR wire harness (except pigtails) is damaged, component can be repaired using one of connector repair assembly packs. Terminals in SIR system are manufactured from a special metal to provide necessary contact for low energy circuits. These terminals are only available in wiring kit, and no other terminal should be substituted.

If an SIR wire pigtail is damaged, entire component (including pigtail) should be replaced. Under no circumstances should wire, connector or terminal repair be attempted on arming sensor, passenger compartment discriminating sensor, forward discriminating sensor, inflator module, or SIR coil assembly.

If any wire except a pigtail is damaged, wire can be repaired by splicing in a new section of wire of same gauge. Sealed splices and crimping tool must be used for these splices. To open wiring harness, remove tape as necessary. To avoid wire insulation damage, manufacturer recommends use of a sewing seam ripper. Refer to instructions in kit for wire repair procedure.

CONNECTOR IDENTIFICATION

Note. To identify SIR wiring connector terminals (Scheme 34)-8.

Scheme 34

Scheme 35

Scheme 36

Scheme 37

TORQUE SPECIFICATIONS

TORQUE SPECIFICATIONS

SIR System Wiring Diagram. Scheme 38

See also:
• PASSIVE RESTRAINT SYSTEM INSPECTION
• COMPUTER RELEARN PROCEDURES