Air Bag Restraint System Buick Roadmaster VIII

CONNECTOR IDENTIFICATION

Note. To identify SIR wiring connector terminals, see appropriate Figs.

Scheme 1

Scheme 2

Scheme 3

Scheme 4

Scheme 5

Scheme 6

DESCRIPTION & OPERATION

The Supplemental Inflatable Restraint (SIR) system is designed to deploy in a frontal collision. The air bag will deploy only upon frontal or near frontal impact of no more than 30 degrees off the centerline of the vehicle. The 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 the sensors in the vehicle to detect this sudden deceleration. These sensors, in turn, trigger the inflator module.

DIAGNOSTIC ENERGY RESERVE MODULE (DERM)

The Diagnostic Energy Reserve Module (DERM) maintains a 36-Volt Loop Reserve (36VLR) energy supply to provide deployment energy for approximately 10-14 minutes if voltage is low or lost in an accident. In addition, the DERM performs diagnostic monitoring of all system components, stores both current and past SIR system Diagnostic Trouble Codes (DTC) information, warns driver of SIR system faults by controlling INFLATABLE RESTRAINT indicator light, and records SIR system status during a vehicle accident.

The DERM is connected to the SIR harness by a 24-pin connector. The harness connector uses gold-plated terminals and a gold-plated shorting bar in the contact area. The DERM connector also has a gold-plated shorting bar to connect INFLATABLE RESTRAINT indicator input to ground when the DERM connector is disconnected. With the DERM disconnected, the INFLATABLE RESTRAINT indicator remains on when ignition switch is turned to RUN or START position. The DERM is located under the instrument panel.

INFLATABLE RESTRAINT INDICATOR LIGHT

When ignition switch is in RUN or START position, battery voltage is applied to the INFLATABLE RESTRAINT indicator light. The Diagnostic Energy Reserve Module (DERM) turns on the light by providing a ground to a lamp driver. The INFLATABLE RESTRAINT indicator light verifies bulb and DERM operation by flashing 7-9 times when ignition is first turned on, warning the driver of SIR electrical system faults which could potentially affect the operation of the SIR system.

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

The arming sensor is a protective switch located in the power feed side (positive side) of the deployment loop. It is calibrated to close at low-level velocity changes (lower than discriminating sensors). This ensures inflator module is connected directly to the 36-Volt Loop Reserve (36VLR) output of the Diagnostic Energy Reserve Module (DERM) and ignition voltage when either discriminating sensor closes.

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

The DERM monitors these voltage drops to detect circuit or component faults. The 2 diodes provide isolation between the 36VLR output of the DERM and ignition voltage. In some models, the arming sensor is combined with the passenger compartment discriminating sensor and is referred to as a dual sensor. On models with dual air bags, this component is referred to as the dual pole arming sensor and provides the same function.

DISCRIMINATING SENSORS

SIR system uses 2 or more discriminating sensors. Some models have 2 forward discriminating sensors; others have one forward discriminating sensor and one passenger compartment sensor. Some models have one forward discriminating sensor and a left or right (engine compartment) discriminating sensor.

The forward discriminating sensor(s) is located on the radiator support brace. The passenger compartment discriminating sensor is located under the center of the instrument panel/console area or under the front passenger seat. The left/right discriminating sensor is located on the left or right frame rail, next to shock tower. In some models, the passenger compartment discriminating sensor is combined with the arming sensor and is known as a dual sensor.

Discriminating sensors are wired in parallel on the ground side of the deployment loop. These sensors are calibrated to close when deceleration velocity changes are severe enough to warrant deployment.

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

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

SIR COIL ASSEMBLY

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

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

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 air bag packed inside the steering wheel hub and an optional or standard passenger-side air bag. The air bag inflates and deploys in less than 1/20 of a second. As the driver contacts the air bag, the gas is vented and deflation occurs.

RESISTOR MODULE

The resistor module is located in SIR harness between inflator module and Diagnostic Energy Reserve Module (DERM). The resistor module allows the DERM to monitor the deployment loop for faults and to detect whether a deployment has occurred.

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

SYSTEM OPERATION CHECK

If system is functioning normally, INFLATABLE RESTRAINT indicator light will flash 7-9 times and then go off when ignition switch is turned to ON position. Four possible indicator light conditions warn of system failure

1. Light does not glow 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 connector at base of steering column and/or under right side of instrument panel.

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.

If DERM sets a Diagnostic Trouble Code (DTC) and diagnostic chart leads to a faulty sensor that was not in area of accident damage, that sensor should also be replaced.

SERVICE PRECAUTIONS

Observe these precautions when working with air bag systems

1. Disable air bag system before servicing any air bag system or steering column component. Failure to do this could result in accidental air bag deployment and possible personal injury. See DISABLING & ACTIVATING AIR BAG SYSTEM.
2. After an accident, inspect all SIR components, including harness and brackets. Replace any damaged or bent components, even if a deployment did not occur. Check steering column, knee bolster, instrument panel steering column reinforcement plate and lower brace for damage. DO NOT service resistor module, inflator module, coil assembly, discriminating sensors, arming sensor or Diagnostic Energy Reserve Module (DERM). Replace these components if damaged or defective.
3. Always wear safety glasses when servicing or handling an air bag.
4. Air bag module must be stored in its original special container until used for service. It must be stored in a clean, dry place, away from sources of extreme heat, sparks or high electrical energy.
5. When placing a live air bag module on a bench or other surface, always face air bag and trim cover up, away from surface. This will reduce motion of module if accidentally deployed.
6. After deployment, air bag surface may contain deposits of sodium hydroxide, which can irritate skin. Always wear safety glasses, rubber gloves and long-sleeved shirt during clean-up, and wash hands using mild soap and water. Follow correct disposal procedures. See DISPOSAL PROCEDURES.
7. At no time should any electrical source be allowed near inflator on back of air bag module.
8. When carrying a live air bag module, trim cover should be pointed away from your body to minimize injury in case of deployment.
9. DO NOT probe a wire through insulator; this will damage it and eventually cause failure due to corrosion.
10. Coil assembly must be replaced whenever air bag deploys.
11. When performing electrical tests, prevent accidental shorting of terminals. Such mistakes can damage fuses or components and may cause a second Diagnostic Trouble Code (DTC) to set, making diagnosis of original problem more difficult.
12. When using diagnostic charts to diagnose air bag system, DO NOT use volt-ohmmeter, test light or any type of electrical equipment not specified by manufacturer. See SPECIAL TOOLS.
13. If air bag system is not fully functional for any reason, vehicle should not be driven until system is repaired. DO NOT remove bulbs, modules, sensors or other components or in any way disable system from operating normally. If air bag system is not functional, park vehicle until repairs can be made.

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 not specified by manufacturer. See SIR RECOMMENDED TOOL table.

SIR RECOMMENDED TOOL

DISABLING & ACTIVATING AIR BAG SYSTEM

1. To disable air bag system, turn ignition switch to OFF position. Remove SIR fuse from fuse block. Disconnect Yellow SIR connector at base of steering column. On models equipped with passenger-side air bag, also disconnect Yellow connector under right side of instrument panel.
2. Wait 10 minutes before working on vehicle. All connectors used on SIR system use Connector Position Assurance (CPA) clips to ensure connector retention.
3. To activate air bag system, turn ignition switch to OFF position. Connect Yellow 2-pin connector and CPA clip at base of steering column and/or under right side of instrument panel. Install SIR fuse. Turn ignition switch to RUN position. Observe INFLATABLE RESTRAINT indicator light. See SYSTEM OPERATION CHECK.

CENTERING COIL ASSEMBLY

1. If coil assembly has been removed from steering column and is being reinstalled, go to step 2). New coil assemblies are provided pre-centered and include a Blue plastic tab, which is snapped off once coil is installed.
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 also has not been rotated.
3. Hold coil assembly with clear bottom upward to see coil ribbon. (Scheme 7) Note that 2 different styles of coil assemblies are used: one rotates clockwise and other rotates 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.

Scheme 7

DEPLOYED AIR BAG

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 air bag modules is regulated by hazardous materials regulations of Department of Transportation (DOT) and most state governments. Special shipping procedures are required. Repair shops should check with hazardous material section of their respective state governments for applicable shipping requirements.

SCRAPPED VEHICLE

Some vehicles to be scrapped may have an undeployed SIR module. Follow these procedures when scrapping such a vehicle

1. Turn ignition switch to OFF position. Remove SIR fuse. Disconnect Yellow 2-pin connector at base of steering column. On passenger-side air bag models, disconnect Yellow 2-pin connector under right side of instrument panel. On all models, 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 as far away from car 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 when handling deployed air bag. Wash hands with soap and water afterward.

REMOVAL & INSTALLATION

Removal

1. Before proceeding, see SERVICE PRECAUTIONS. Disable air bag system. See DISABLING & ACTIVATING AIR BAG SYSTEM.
2. DERM is located under left side of instrument panel. Remove electronic brake control module. Remove bolt from DERM bracket. Remove DERM and bracket. Remove DERM by lowering front part of DERM from bracket and pulling DERM outward. (Scheme 8) Disconnect DERM electrical connector.

Installation

Reconnect DERM electrical connector. Install DERM by inserting rear DERM bolts into holes in bracket and pushing front part of DERM up, snapping it into bracket. Tighten nut to 17 INCH lbs. (2 N.m). Install DERM bolts, and tighten to 53 INCH lbs. (6 N.m). To complete installation, reverse removal procedure. Ensure system is functioning properly. See SYSTEM OPERATION CHECK.

Scheme 8

1. Before proceeding, see SERVICE PRECAUTIONS. Disable air bag system. See DISABLING & ACTIVATING AIR BAG SYSTEM.
2. Arming sensor is located under left side of instrument panel. Remove twilight sentinel module from bracket (if equipped). Reposition dash mat to access arming sensor. Remove Connector Position Assurance (CPA) clip by moving it upward while holding electrical connector body. Remove arming sensor electrical connector from body harness connector, located near top of instrument panel. Remove arming sensor mounting screws. Remove sensor. (Scheme 9)

Install arming sensor. Tighten mounting screws to specification. See TORQUE SPECIFICATIONS TABLE at the end of this article. To complete installation, reverse removal procedure. Ensure system is functioning properly. See SYSTEM OPERATION CHECK.

Scheme 9

1. Before proceeding, see SERVICE PRECAUTIONS. Disable air bag system. See DISABLING & ACTIVATING AIR BAG SYSTEM.
2. Forward discriminating sensor is located on radiator brace. Remove battery, if necessary, to access right forward discriminating sensor. Remove radiator support baffle from radiator. Disconnect electrical connector, and remove Connector Position Assurance (CPA) clip from radiator support. Remove screws and left/right discriminating sensor. (Scheme 10)

Install left/right forward discriminating sensor so arrow points toward front of vehicle. Install and tighten sensor attaching screws to 25 INCH lbs. (2.8 N.m). To complete installation, reverse removal procedure. Ensure system is functioning properly. See SYSTEM OPERATION CHECK.

Scheme 10

1. Before proceeding, see SERVICE PRECAUTIONS. Disable air bag system. See DISABLING & ACTIVATING AIR BAG SYSTEM.
2. SIR coil assembly is located under steering wheel, in steering column. Remove inflator module. See DRIVER-SIDE INFLATOR MODULE. Remove horn contact wire from steering column. Remove steering wheel hexagon locking nut. Using a puller, remove steering wheel. 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 it 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), 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. 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.

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.

1. Carefully feed coil assembly wire and lower connector through lock housing cover, column housing and gear shift lever bowl, and allow coil assembly to hang freely. Ensure slack is never present in coil assembly wire in steering column, otherwise coil assembly wire damage may occur.
2. Install turn signal switch and switch arm. Tighten attaching screws to specification. See TORQUE SPECIFICATIONS TABLE at the end of this article.
3. Install hazard knob and attaching screw, 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. Ensure coil assembly hub and steering shaft are centered. Coil assembly will become uncentered if column is separated from steering gear and allowed to rotate or if centering spring is depressed, allowing hub to rotate while coil assembly is removed from column.
4. 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. Ensure system is functioning properly. See SYSTEM OPERATION CHECK.

1. Before proceeding, see SERVICE PRECAUTIONS. Disable air bag system. See DISABLING & ACTIVATING AIR BAG SYSTEM.
2. Inflator module is located on steering wheel hub. Remove screws and nuts from underside of steering wheel. Partially remove inflator module, and disconnect steering wheel inflator module connector, Connector Position Assurance (CPA) clip and horn contact from inflator. Remove inflator module.

1. Install horn contact, steering wheel inflator module connector and CPA clip. Install inflator module to steering wheel.
2. On Corvette, tighten screws to 87 INCH lbs. (9.7 N.m); on all other models, tighten screws to 27 INCH lbs. (3.1 N.m). To complete installation, reverse removal procedure. Ensure system is functioning properly. See SYSTEM OPERATION CHECK.

1. Before proceeding, see SERVICE PRECAUTIONS. Disable air bag system. See DISABLING & ACTIVATING AIR BAG SYSTEM.
2. Resistor module is located under left side of instrument panel, behind left kick panel. (Scheme 11) Remove Connector Position Assurance (CPA) clip, disconnect electrical connector and slide module from mounting. To install, reverse removal procedure. Ensure system is functioning properly. See SYSTEM OPERATION CHECK.

Scheme 11

DIAGNOSIS & TESTING

Trouble Codes/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 flash code diagnostics provided through INFLATABLE RESTRAINT indicator light, a Scan tester such as Tech 1, or on-board diagnostics on vehicles with an on-board diagnostics panel.

Flash Code Diagnostics

Flash code diagnostics can only be used to read current diagnostic trouble codes and determine if history codes are present. Flash code diagnostics cannot be used to clear codes or read history codes. Flash code diagnosis is enabled by grounding terminal "K" of Assembly Line Diagnostic Link (ALDL) connector/Data Link Connector (DLC), located under instrument panel, with ignition switch in ON position. Grounding terminal "K" signals Diagnostic Energy Reserve Module (DERM) to enter flash code diagnostic display mode.

DERM identifies 2-digit trouble codes by activating INFLATABLE RESTRAINT indicator via a lamp driver at SIR indicator low output. Each code displayed will consist of a number of flashes representing tens for first digit, a 1/2-second pause, and a number of flashes representing ones for second digit. Each code is flashed once. After all codes have been displayed, entire code sequence will repeat until ground is removed from terminal "K" of ALDL/DLC connector.

Two special codes (Codes 12 and 13) exist when reading flash code mode. Code 12 will always be first code displayed when flash code mode is entered. Code 12 does not indicate a fault; it indicates flash code mode has been enabled. If no current or history codes are present, DERM will display Code 12 until ground is removed from ALDL/DLC connector at terminal "K". Code 13 will be displayed if history codes are present. To read history codes, use a scan tester.

Scan Tester Diagnostics

Scan tester must be used along with Inflator Module Load Tool (J-37808). 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 ALDL/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 ALDL/DLC connector.

On-Board Diagnostics

On-board diagnostics can only be used on models with on-board diagnostics panel. Enter diagnostics by depressing WARMER and OFF buttons on diagnostics panel. (Scheme 12) 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 if 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.

Scheme 12

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 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 SIR fuse to Diagnostic Energy Reserve Module (DERM) at IGNITION 1 input terminals A3 and B3 and from fuse No. 17 to DERM at SIR INDICATOR HIGH input. DERM responds by flashing INFLATABLE RESTRAINT indicator 7-9 times.

When engine is cranked, system voltage is applied from fuse No. 20 to DERM at CRANK input. DERM grounds light circuit until system voltage is removed from CRANK input. This results in a steady INFLATABLE RESTRAINT indicator during cranking. After engine is cranked, DERM will again flash INFLATABLE RESTRAINT indicator 7-9 times.

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

1. INFLATABLE RESTRAINT indicator should flash 7-9 times after ignition is first turned on.
2. INFLATABLE RESTRAINT indicator should remain on steady during cranking.
3. After cranking, INFLATABLE RESTRAINT indicator should flash 7-9 times and then go off.
4. INFLATABLE RESTRAINT warning light has successfully completed bulb check.
5. Test checks for proper operation of SERIAL DATA circuit. This test will also determine which history codes, if any, are stored.
6. Incorrect operation of INFLATABLE RESTRAINT warning light is indicated. Test differentiates a warning light stays on condition from a warning light does not come on condition.
7. Test differentiates a current fault code exists condition from a diagnostics enabled when not requested condition.
8. INFLATABLE RESTRAINT warning light has completed bulb check and indicates current fault codes exist.
9. Test checks for proper operation of SERIAL DATA circuit. Test also indicates which fault codes are stored and whether they are current or history.

Scheme 13

When system voltage is applied to it, DERM will perform TURN-ON tests followed by CONTINUOUS MONITORING tests. If no faults are detected, DERM will perform a STEERING COLUMN RESISTANCE test. When a fault is detected , DERM will store a current code and illuminate INFLATABLE RESTRAINT warning light. DERM will clear current codes and store them as history codes when fault is no longer detected or when ignition switch is cycled, except for Code 51. Current Code 51 can only be cleared using a Tech 1 and will then be stored as a history code. History Code 51 can be cleared for current ignition on-cycle but will reappear at next ignition on-cycle.

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

1. DERM has detected an event in which SENSE HIGH voltage was above a certain percentage of deployment loop voltage and, simultaneously, SENSE LOW voltage was below a certain percentage of deployment loop voltage.
2. Checks for intermittent conditions within steering column.
3. Checks for intermittent shorts in 36-Volt Loop Reserve (36VLR) wiring (circuit No. 236).
4. Checks for improperly installed fuse No. 17 and INFLATABLE RESTRAINT indicator bulb or uncleared Code 61 after a completed wiring repair on circuit No. 39. Also checks for intermittent faults in circuits No. 688 and 358.
5. Checks for intermittent opens in ground path of deployment loop between base of steering column and both discriminating sensors.
6. Checks for intermittent wiring shorts between 36-Volt Loop Reserve (36VLR) circuit No. 236 and circuits No. 347, 348 and 349 of SIR wiring harness.

Scheme 14

When system voltage is applied to it, DERM will perform TURN-ON tests followed by CONTINUOUS MONITORING tests. If no faults are detected, DERM will perform a STEERING COLUMN RESISTANCE test. When a fault is detected, DERM will store a current code and illuminate INFLATABLE RESTRAINT warning light. DERM will clear current codes and store them as history codes when fault is no longer detected or when ignition switch is cycled, except for Code 51. Current Code 51 can only be cleared using a Tech 1 and will then be stored as a history code. History Code 51 can be cleared for current ignition on-cycle but will reappear at next ignition on-cycle.

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

1. 7) Checks for intermittent shorts to system voltage in 36VLR wiring (circuit No. 236).
2. 8) Checks for intermittent shorts to ground in 36VLR wiring (circuit No. 236).
3. 9) Checks for intermittent open in 36VLR wiring (circuit No. 236).
4. 10) Checks for intermittent open in FORCE HI and FORCE LOW wiring (circuits No. 714 and 688).
5. 11) Checks for intermittent opens or shorts to ground in SENSE LOW wiring (circuit No. 752).
6. 12) Checks for shorts to system voltage in deployment loop (circuits No. 347, 348 and 349) or in diagnostic circuits (circuits No. 347, 348, 688, 714, 752 and 753).
7. 13) Checks for shorts between circuits No. 236 and 347, 348 and 349.

Scheme 15

When system voltage is applied to it, DERM will perform TURN-ON tests followed by CONTINUOUS MONITORING tests. If no faults are detected, DERM will perform a STEERING COLUMN RESISTANCE test. When a fault is detected, DERM will store a current code and illuminate INFLATABLE RESTRAINT warning light. DERM will clear current codes and store them as history codes when fault is no longer detected or when ignition switch is cycled, except for Code 51. Current Code 51 can only be cleared using a Tech 1 and will then be stored as a history code. History Code 51 can be cleared for current ignition on-cycle but will reappear at next ignition on-cycle.

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

1. 14) Checks for intermittent opens on 36-Volt Loop Reserve (36VLR) wiring (circuit No. 236).
2. 15) Checks for intermittent open between fuse No. 12 and arming sensor (circuit No. 1139).

Scheme 16

When ignition is first turned on, system voltage is applied from fuse No. 17 to SIR INDICATOR HIGH and INFLATABLE RESTRAINT indicator light, which is connected to SIR INDICATOR LOW. Fuse No. 12 also applies system voltage to IGNITION 1 inputs A3 and B3. Diagnostic Energy Reserve Module (DERM) responds by flashing INFLATABLE RESTRAINT indicator 7-9 times.

When engine is cranked, system voltage is applied to DERM at CRANK input. DERM grounds light circuit until system voltage is removed from CRANK input. This results in a steady INFLATABLE RESTRAINT indicator during cranking. After engine is cranked, DERM will again flash INFLATABLE RESTRAINT indicator 7-9 times.

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

1. Test determines whether flash code diagnostics can be enabled.
2. Test checks for a good ground at ALDL connector.
3. Test checks for an open in DIAGNOSTIC REQUEST circuit.
4. Test checks for a short to voltage in DIAGNOSTIC REQUEST circuit.
5. Test determines whether further diagnosis is required.
6. Test determines whether only history or both current and history codes exist.

Scheme 17

When ignition is first turned on, system voltage is applied from fuse No. 17 to SIR INDICATOR HIGH and to INFLATABLE RESTRAINT indicator light, which is connected to SIR INDICATOR LOW. Fuse No. 12 also applies system voltage to IGNITION 1 inputs A3 and B3. Diagnostic Energy Reserve Module (DERM) responds by flashing INFLATABLE RESTRAINT indicator 7-9 times.

When engine is cranked, system voltage is applied to DERM at CRANK input. DERM grounds light circuit until system voltage is removed from CRANK input. This results in a steady INFLATABLE RESTRAINT indicator during cranking. After engine is cranked, DERM will again flash INFLATABLE RESTRAINT indicator 7-9 times.

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

1. An open fuse No. 12 would result in a loss of IGNITION 1 voltage at DERM. DERM will respond by grounding light circuit (SIR INDICATOR LOW) whenever ignition is on.
2. If DERM and SIR harness connector are disconnected, shorting bar between terminals A1 and B1 of harness connector will ground light circuit.
3. Checks for a short from SIR INDICATOR LOW circuit to ground.
4. Checks if an open exists in IGNITION 1 circuitry to DERM.
5. Checks for a short from CRANK input circuit to voltage.
6. Checks whether a short to ground caused fuse No. 12 to open.
7. Test determines whether short to ground is due to faulty arming sensor or a short in wiring.

Scheme 18

When ignition is first turned on, system voltage is applied from fuse No. 17 to SIR INDICATOR HIGH and INFLATABLE RESTRAINT indicator light, which is connected to SIR INDICATOR LOW. Fuse No. 12 applies system voltage to IGNITION 1 inputs A3 and B3. Diagnostic Energy Reserve Module (DERM) responds by flashing INFLATABLE RESTRAINT indicator 7-9 times.

When engine is cranked, system voltage is applied to DERM at CRANK input. DERM grounds SIR INDICATOR LOW output until system voltage is removed from CRANK input. This results in a steady INFLATABLE RESTRAINT indicator during cranking. After engine is cranked, DERM will again flash INFLATABLE RESTRAINT indicator 7-9 times.

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

1. Checks whether fault is in instrument cluster or wiring.
2. Checks whether fault is in power feed to instrument cluster.
3. Checks for an open in SIR INDICATOR LOW circuit.
4. Checks for a short from SIR INDICATOR LOW circuit to voltage.
5. Checks for a good ground to DERM. If ground is good, DERM is faulty.
6. Checks whether fault is due to a bad fuse.
7. Checks whether a circuitry fault opened fuse.
8. Checks whether circuitry fault is internal to DERM.

Scheme 19

When ignition is first turned on, system voltage is applied from fuse No. 17 to SIR INDICATOR HIGH and INFLATABLE RESTRAINT indicator light, which is connected to SIR INDICATOR LOW. Fuse No. 12 applies system voltage to IGNITION 1 inputs A3 and B3. Diagnostic Energy Reserve Module (DERM) responds by flashing INFLATABLE RESTRAINT indicator 7-9 times.

When engine is cranked, system voltage is applied to DERM at CRANK input. DERM grounds SIR INDICATOR LOW output until system voltage is removed from CRANK input. This results in a steady INFLATABLE RESTRAINT indicator during cranking. After engine is cranked, DERM will again flash INFLATABLE RESTRAINT indicator 7-9 times.

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

1. 9) Checks whether fault is due to a bad bulb.
2. 10) Checks for an open in SIR INDICATOR HIGH circuit and instrument cluster power feed circuit.
3. 11) Test determines whether open is in SIR INDICATOR LOW circuit or instrument cluster printed circuit.

Scheme 20

When ignition is first turned on, system voltage is applied from fuse No. 17 to SIR INDICATOR HIGH and INFLATABLE RESTRAINT indicator light, which is connected to SIR INDICATOR LOW. Fuse No. 12 also applies system voltage to IGNITION 1 inputs A3 and B3. Diagnostic Energy Reserve Module (DERM) responds by flashing INFLATABLE RESTRAINT indicator 7-9 times. Shorting bar is provided to illuminate INFLATABLE RESTRAINT indicator light should DERM become disconnected.

When engine is being cranked, system voltage is applied to DERM at CRANK input. DERM grounds light circuit until system voltage is removed from CRANK input. This results in a steady INFLATABLE RESTRAINT indicator during cranking.

After engine is cranked, DERM will again flash INFLATABLE RESTRAINT indicator 7-9 times if ignition is on.

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 fuse No. 20.
2. Checks for a proper signal to CRANK input during cranking.
3. Test determines whether lack of proper crank signal is due to an open CRANK input circuit or an open power feed to fuse No. 20.
4. Checks whether fuse No. 20 is open due to a short to ground in CRANK input circuit.
5. Checks whether short to ground is in wiring harness or DERM.

Scheme 21

When ignition is first turned on, system voltage is applied from fuse No. 17 to SIR INDICATOR HIGH and INFLATABLE RESTRAINT indicator light, which is connected to SIR INDICATOR LOW. Fuse No. 12 applies system voltage to IGNITION 1 inputs A3 and B3. Diagnostic Energy Reserve Module (DERM) responds by flashing INFLATABLE RESTRAINT indicator 7-9 times.

When engine is being cranked, system voltage is applied to DERM at CRANK input. DERM grounds light circuit until system voltage is removed from CRANK input. This results in a steady INFLATABLE RESTRAINT indicator during cranking. After engine is cranked, DERM will again flash INFLATABLE RESTRAINT indicator 7-9 times if ignition is on.

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

Checks for a short to ground on DIAGNOSTIC REQUEST circuit. Because grounding of DIAGNOSTIC REQUEST (circuit No. 326) enables diagnostics, this ground must be supplied by DERM or wiring.

Scheme 22

When ignition is first turned on, system voltage is applied from fuse No. 17 to SIR INDICATOR HIGH and INFLATABLE RESTRAINT indicator light, which is connected to SIR INDICATOR LOW. Fuse No. 12 applies system voltage to IGNITION 1 inputs A3 and B3. Diagnostic Energy Reserve Module (DERM) responds by flashing INFLATABLE RESTRAINT indicator 7-9 times.

When engine is being cranked, system voltage is applied to DERM at CRANK input. DERM grounds light circuit until system voltage is removed from CRANK input. This results in a steady INFLATABLE RESTRAINT indicator during cranking. After engine is cranked, DERM will again flash INFLATABLE RESTRAINT indicator 7-9 times if ignition is on.

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

1. Incorrect connection to ALDL connector will prevent communications from being established.
2. Correct BODY SYSTEMS cartridge must be used.
3. Checks for a short to ground on SERIAL DATA circuit.
4. Checks for an open in SERIAL DATA circuit.
5. Checks for a short to voltage on SERIAL DATA circuit.

Scheme 23

Diagnostic Energy Reserve Module (DERM) injects a current through steering column from FORCE HI output (terminal A4) to FORCE LOW output (terminal A10). By monitoring voltage at SENSE HI input (terminal A7) and SENSE LOW input (terminal A6), DERM calculates combined resistance of inflator module, SIR coil, harness wiring (circuits No. 347 and 348) and terminal contact in steering column.

Test Conditions

Tested once each ignition cycle during STEERING COLUMN RESISTANCE test if

1. No faults are detected during TURN-ON.
2. No faults are detected during CONTINUOUS MONITORING for one second.
3. No crank signal is present.
4. IGNITION 1 voltage is present.

Failure Conditions

Code 21 will set if combined resistance of wiring and connector terminal contact in steering column is greater than a specified value. Code 21 will also set if 100-ohm resistor within resistor module is shorted.

Conditions To Clear

Code 21 will clear each time ignition is turned off.

Action Taken

DERM turns on INFLATABLE RESTRAINT indicator light.

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

1. Checks if fault is in steering column. SIR Load Tester (J-37808) simulates resistance of good steering column wiring and components.
2. Determines if fault is in resistor module.
3. Checks resistors in resistor module.
4. Checks resistor module for internal failures.
5. Checks steering column for faults.

Scheme 24

DERM injects a current of 75 milliamperes through steering column from FORCE HI output (terminal A4) to FORCE LOW input (terminal A10). By monitoring voltage at SENSE HI input (terminal A7) and SENSE LOW input (terminal A6), DERM calculates combined resistance of inflator module, SIR coil, harness wiring (circuits No. 347 and 348) and connector terminal contact in steering column. Code 21 will set if resistance of inflator module, SIR coil, harness wiring and connector terminal contact in steering column is greater than a specified value.

Tested once each ignition cycle during STEERING COLUMN RESISTANCE test if

1. No faults are detected during TURN-ON.
2. No faults are detected during CONTINUOUS MONITORING for one second.
3. No crank signal is present.
4. IGNITION 1 voltage is present.

Code 21 will set if combined resistance of inflator module, SIR coil, harness wiring and connector terminal contact in steering column is greater than a specified value.

Code 21 will clear each time ignition is turned off.

DERM turns on INFLATABLE RESTRAINT indicator light.

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

1. 6) Checks integrity of circuits No. 347A, 348B and inflatable restraint wiring harness to SIR coil connection.
2. 7) Checks for a short from FORCE HIGH circuit to SENSE HIGH circuit.
3. 8) Checks for a short from SENSE HIGH circuit to voltage.
4. 9) Checks whether fault is in circuit No. 347A or 348B.

Scheme 25

Diagnostic Energy Reserve Module (DERM) injects a current through steering column from FORCE HI output (terminal A4) to FORCE LOW output (terminal A10). By monitoring voltage at SENSE HI input (terminal A7) and SENSE LOW input (terminal A6), DERM calculates combined resistance of inflator module, SIR coil, harness wiring (circuits No. 347 and 348) and connector terminal contact in steering column.

Tested once each ignition cycle during STEERING COLUMN RESISTANCE test if

1. No faults are detected during TURN-ON.
2. No faults are detected during CONTINUOUS MONITORING for one second.
3. No crank signal is present.
4. IGNITION 1 voltage is present.

Code 22 will set if combined resistance of inflator module, SIR coil, harness wiring and connector terminal contact in steering column is less than a specified value.

Code 22 will clear each time ignition is turned off.

DERM turns on INFLATABLE RESTRAINT indicator light.

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

1. Checks if fault is in steering column or diagnostic circuitry.
2. Checks integrity of 430-ohm resistor and associated circuitry in resistor module.
3. Checks integrity of 49.9-ohm resistor, 100-ohm resistor and associated circuitry in resistor module.
4. Checks integrity of two 2490-ohm resistors and associated circuitry in resistor module.
5. Checks whether steering column fault is due to SIR coil or inflator module.

Scheme 26

DERM injects a current through steering column from FORCE HI output (terminal A4) to FORCE LOW output (terminal A10). By monitoring voltage at SENSE HI input (terminal A7) and SENSE LOW input (terminal A6), DERM calculates combined resistance of inflator module, SIR coil, harness wiring (circuits No. 347 and 348) and connector terminal contact in steering column.

Tested once each ignition cycle during STEERING COLUMN RESISTANCE test if

1. No faults are detected during TURN-ON.
2. No faults are detected during CONTINUOUS MONITORING for one second.
3. No crank signal is present.
4. IGNITION 1 voltage is present.

Code 22 will set if combined resistance of inflator module, SIR coil, harness wiring and connector terminal contact in steering column is less than a specified value.

Code 22 will clear each time ignition is turned off.

DERM turns on INFLATABLE RESTRAINT indicator light.

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

1. 6) Checks for a short from circuit No. 347 to circuit No. 348.
2. 7) Checks for an open in SENSE HI circuit.
3. 8) Checks for a short from SENSE HI circuit to FORCE LOW circuit.
4. 9) Checks for a short from SENSE LOW circuit to FORCE HI circuit.
5. 10) Checks for a short from SENSE LOW circuit to SENSE HI circuit.

Scheme 27

Diagnostic Energy Reserve Module (DERM) injects a current through steering column from FORCE HI output (terminal A4) to FORCE LOW input (terminal A10). By monitoring voltage at SENSE HI input (terminal A7) and SENSE LOW input (terminal A6), DERM calculates combined resistance of inflator module, SIR coil, circuits No. 347 and 348, and connector terminal contact in steering column. Codes 21 and 22 will set if voltage at SENSE LOW input (terminal A6) is less than a certain voltage during STEERING COLUMN RESISTANCE test. This results in an undetermined steering column resistance.

Tested once each ignition cycle during STEERING COLUMN RESISTANCE test if

1. No faults are detected during TURN-ON.
2. No faults are detected during CONTINUOUS MONITORING for one second.
3. No crank signal is present.
4. IGNITION 1 voltage is present.

Codes 21 and 22 will set if voltage at SENSE LOW input (terminal A6) is less than a certain voltage during STEERING COLUMN RESISTANCE test. This results in an undetermined steering column resistance.

Current Codes 21 and 22 will be cleared each time ignition is turned off.

DERM turns on INFLATABLE RESTRAINT indicator light.

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

1. Checks integrity of 49.9-ohm resistor, 100-ohm resistor, 430-ohm resistor and associated circuitry in resistor module.
2. Checks integrity of 430-ohm resistor, SENSE LOW resistor and associated circuitry in resistor module.
3. Checks for a short from circuit No. 348 or 349 to FORCE LOW circuit.
4. Checks for an open in FORCE HI circuit.
5. Checks for a short from FORCE LOW circuit to FORCE HI circuit.
6. Checks for a short from FORCE LOW circuit to SENSE LOW circuit.

Scheme 28

Code 23 is set when voltage at SENSE LOW input (terminal A6) is greater than a specific percentage of 36-Volt Loop Reserve (36VLR) for 500 milliseconds during CONTINUOUS MONITORING tests performed by Diagnostic Energy Reserve Module (DERM). CONTINUOUS MONITORING tests are performed by DERM after initial TURN-ON tests are completed and every 100 milliseconds while IGNITION 1 voltage is present at DERM. CONTINUOUS MONITORING tests check continuity of deployment loop from 36VLR of DERM through arming sensor, inflator module and discriminating sensors to ground. Code 23 indicates a shorted arming sensor, shorted harness or an open in low side of deployment loop.

Tested every 100 milliseconds during CONTINUOUS MONITORING.

Code 23 will set if voltage at SENSE LOW input (terminal A6) is greater than a specific percentage of 36VLR for 500 milliseconds.

Current Code 23 will clear if voltage at SENSE LOW input (terminal A6) is within a specific range of 36VLR output voltage for 500 milliseconds (5 consecutive CONTINUOUS MONITORING cycles) after Code 23 has been set.

DERM turns on INFLATABLE RESTRAINT indicator light.

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

1. Checks integrity of low side of deployment loop between steering column and left forward discriminating sensor.
2. Checks for an open in left forward discriminating sensor between terminal "A" and splice.
3. Checks for a short from 36VLR circuit to FORCE HI circuit.
4. Checks for a short from 36VLR circuit to SENSE LOW circuit.
5. Checks for a short from 36VLR circuit to FORCE LOW circuit.

Scheme 29

Code 23 is set when voltage at SENSE LOW input (terminal A6) is greater than a specific percentage of 36VLR for 500 milliseconds during CONTINUOUS MONITORING tests performed by DERM. CONTINUOUS MONITORING tests are performed by DERM after initial TURN-ON tests are completed and every 100 milliseconds while IGNITION 1 voltage is present at DERM. CONTINUOUS MONITORING tests check continuity of deployment loop from 36VLR of DERM through arming sensor, inflator module and discriminating sensors to ground. Code 23 indicates a shorted arming sensor, short to 36-Volt Loop Reserve (36VLR) or an open in low side of deployment loop.

Tested every 100 milliseconds during CONTINUOUS MONITORING.

Code 23 will set if voltage at SENSE LOW input (terminal A6) is greater than a specific percentage of 36VLR for 500 milliseconds.

Current Code 23 will clear if voltage at SENSE LOW input (terminal A6) is within a specific range of 36VLR output voltage for 500 milliseconds (5 consecutive CONTINUOUS MONITORING cycles) after Code 23 has been set.

DERM turns on INFLATABLE RESTRAINT indicator light.

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

1. 6) Checks for short from 36VLR circuit to circuit No. 347.
2. 7) Checks for short from 36VLR circuit to circuit No. 347.
3. 8) Code is being set by arming sensor which is latched closed, a partial short across arming sensor diagnostic resistor or a faulty DERM.

Scheme 30

Code 24 is set when voltage at SENSE LOW input (terminal A6) is within a specific range of 36-Volt Loop Reserve (36VLR) output voltage for 500 milliseconds during CONTINUOUS MONITORING tests performed by Diagnostic Energy Reserve Module (DERM). CONTINUOUS MONITORING tests are performed by DERM after initial TURN-ON tests are completed and every 100 milliseconds while IGNITION 1 voltage is present at DERM. CONTINUOUS MONITORING tests check continuity of deployment loop from 36VLR of DERM through arming sensor, inflator module and discriminating sensors to ground.

Tested every 100 milliseconds during CONTINUOUS MONITORING.

Code 24 will set if voltage at SENSE LOW input is within a specific range of 36VLR output voltage for 500 milliseconds.

Code 24 will clear if voltage at SENSE LOW input (terminal A6) is within a specific range of 36VLR for 500 milliseconds.

DERM turns on INFLATABLE RESTRAINT indicator light.

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

1. Determines if fault is in steering column or diagnostic circuitry.
2. Checks integrity of IGNITION 1 feed to high side of deployment loop.
3. Checks integrity of SENSE LOW resistor and associated circuitry in resistor module.
4. Checks for an open in SENSE LOW circuit.
5. Checks whether steering column fault is due to SIR coil or inflator module.

Scheme 31

Code 24 is set when voltage at SENSE LOW input (terminal A6) is within a specific range of 36VLR for 500 milliseconds during CONTINUOUS MONITORING tests performed by DERM. CONTINUOUS MONITORING tests are performed by DERM after initial TURN-ON tests are completed and every 100 milliseconds while IGNITION 1 voltage is present at DERM. CONTINUOUS MONITORING tests check continuity of deployment loop from 36VLR of DERM through arming sensor, inflator module and discriminating sensors to ground.

Tested every 100 milliseconds during CONTINUOUS MONITORING.

Code 24 will set if arming sensor resistance is too high or open, discriminating sensor resistance is too low or shorted, FORCE HI, SENSE LOW or FORCE LOW circuits are shorted to ground or system voltage or SENSE HI circuit is shorted to ground.

Code 24 will clear if voltage at SENSE LOW input (terminal A6) is within a specific range of 36VLR for 500 milliseconds.

DERM turns on INFLATABLE RESTRAINT indicator light.

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

1. 6) Checks for an open in circuit No. 347.
2. 7) Checks for a short from circuit No. 347 to ground.
3. 8) Checks for a short from circuit No. 348 or 349 to ground.
4. 9) Checks for a short from FORCE LOW circuit to ground.
5. 10) Checks for a short from FORCE HI circuit to ground.
6. 11) Checks for a short from SENSE LOW circuit to ground.
7. 12) Checks for a short from SENSE HI circuit to ground.
8. 13) Checks for proper resistance of right forward discriminating sensor.
9. 14) Checks for proper resistance of left forward discriminating sensor.

Scheme 32

Code 24 is set when voltage at SENSE LOW input (terminal A6) is within a specific range of 36VLR for 500 milliseconds during CONTINUOUS MONITORING tests performed by DERM. CONTINUOUS MONITORING tests are performed by DERM after initial TURN-ON tests are completed and every 100 milliseconds while IGNITION 1 voltage is present at DERM. CONTINUOUS MONITORING tests check continuity of deployment loop from 36VLR of DERM through arming sensor, inflator module and discriminating sensors to ground.

Tested every 100 milliseconds during CONTINUOUS MONITORING.

Code 24 will set if voltage at SENSE LOW input, terminal A6, is within a specific range of 36VLR output voltage for 500 milliseconds.

Code 24 will clear if voltage at SENSE LOW input (terminal A6) is within a specific range of 36VLR for 500 milliseconds.

DERM turns on INFLATABLE RESTRAINT indicator light.

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

1. 15) Checks for a short from circuit No. 347 to voltage.
2. 16) Checks for a short from circuit No. 348 or 349 to voltage.
3. 17) Checks for a short from FORCE LOW circuit to voltage.
4. 18) Checks for a short from FORCE HI circuit to voltage.
5. 19) Checks for a short from SENSE LOW circuit to voltage.
6. 20) Checks for proper resistance of right forward discriminating sensor.
7. 21) Checks for proper resistance of left forward discriminating sensor.

Scheme 33

Diagnostic Energy Reserve Module (DERM) grounds FORCE LOW output (terminal A10) and then monitors voltage at SENSE LOW input (terminal A6). If voltage at SENSE LOW input is within a specific range of IGNITION 1, Code 25 will set. Code 25 is an indication of a short to voltage on steering column or in circuits No. 347, 348 or 349. In addition, this code can be set if resistance of 100-ohm resistor in resistor module is too high.

Tested once each ignition cycle during STEERING COLUMN RESISTANCE test if

1. No faults are detected during TURN-ON.
2. No faults are detected during CONTINUOUS MONITORING for one second.
3. No crank signal is present.
4. IGNITION 1 voltage is present.

Code 25 will set if voltage at SENSE LOW input (terminal A6) is within a specific range of IGNITION 1 voltage during first portion of STEERING COLUMN RESISTANCE test.

Current Code 25 will be cleared each time ignition is turned off.

DERM turns on INFLATABLE RESTRAINT indicator light.

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

1. Test removes steering column from system. If Code 25 is still current, problem is not in steering column.
2. Checks for a short to voltage in circuit No. 347.
3. Checks for a short to voltage in circuit No. 348 or 349.
4. Checks for a short to voltage in FORCE LOW circuit.
5. Checks for proper resistance of FORCE LOW resistor in resistor module.
6. Because steering column is setting this code, replacing inflator module or SIR coil is necessary.

Scheme 34

If an open exists in SIR coil, inflator module or wiring in steering column, resistance between SENSE HI input (terminal A7) and SENSE LOW input (terminal A6) increases. This increased resistance causes a larger voltage drop from SENSE HI input to SENSE LOW input across 430-ohm resistor in resistor module. Increase in voltage between SENSE HI input and SENSE LOW input is sensed by Diagnostic Energy Reserve Module (DERM) during CONTINUOUS MONITORING test and Code 26 is set.

Tested every 100 milliseconds during CONTINUOUS MONITORING.

Code 26 will set if voltage at SENSE HI input (terminal A7) minus voltage at SENSE LOW input (terminal A6) is greater than a certain voltage for 500 milliseconds.

Code 26 will clear if voltage at SENSE HI input (terminal A7) minus voltage at SENSE LOW input (terminal A6) is greater than zero volts but less than a certain voltage for 500 milliseconds after Code 26 has been set.

DERM turns on INFLATABLE RESTRAINT indicator light.

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

1. Checks if fault is in steering column or diagnostic circuitry.
2. Checks for a short from 36VLR circuit to SENSE HI circuit.
3. Checks whether steering column fault is due to SIR coil or inflator module.

Scheme 35

Voltage at SENSE LOW input (terminal A6) is within a specific range of 36-Volt Loop Reserve (36VLR) output when 36VLR output of Diagnostic Energy Reserve Module (DERM) is functional. Should circuit open between 36VLR output and arming sensor, IGNITION 1 voltage will supply deployment loop. Voltage at SENSE LOW input (terminal A6) will decrease due to lower supply voltage and Code 31 will set after 700 milliseconds (if Code 42 is not set). Code 31 indicates an open in wiring between 36VLR output of DERM and arming sensor.

Tested every 100 milliseconds during CONTINUOUS MONITORING.

Code 31 will set if voltage at SENSE LOW input is within a specific range of 36VLR output voltage for 500 milliseconds.

Current Code 31 will clear if voltage at SENSE LOW input is within a specific range of 36VLR output voltage for 500 milliseconds.

DERM turns on INFLATABLE RESTRAINT indicator light.

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

1. Checks whether DERM has set code falsely.
2. Checks whether 36VLR is available at arming sensor.
3. Checks whether fault is an open in arming sensor or poor connection to arming sensor.

Scheme 36

Voltage at SENSE LOW input (terminal A6) is within a specific range of 36-Volt Loop Reserve (36VLR) output voltage when 36VLR of Diagnostic Energy Reserve Module (DERM) is charged. Should circuit short to ground between 36VLR output and diode in arming sensor connected to terminal "B", IGNITION 1 voltage will supply deployment loop. Voltage at SENSE LOW input (terminal A6) will decrease due to decrease in supply voltage and Code 32 will set after 700 milliseconds. Code 32 indicates a short to ground in wiring between 36VLR of DERM and arming sensor.

Tested every 100 milliseconds during CONTINUOUS MONITORING.

Code 32 will set if voltage at SENSE LOW input (terminal A6) is within a specific range of IGNITION 1 voltage for 700 milliseconds and Code 42 is set.

Current Code 32 will clear if voltage at SENSE LOW input (terminal A6) is within a specific range of 36VLR output voltage for 500 milliseconds.

DERM turns on INFLATABLE RESTRAINT indicator light.

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

1. Checks for a short to ground in 36VLR circuit to ground.
2. Checks whether fault is an internal short to ground in arming sensor or a fault in wiring harness.

Scheme 37

At TURN-ON, Diagnostic Energy Reserve Module (DERM) monitors voltage at 36-Volt Loop Reserve (36VLR) output before this output begins to change. If diode in arming sensor connected to terminal "B" is shorted, IGNITION 1 voltage will be present at 36VLR output (terminal A2) as soon as ignition is turned on. If DERM detects voltage 3 ignition cycles in a row, History Code 33 will be set.

Tested once during each ignition cycle at TURN-ON.

History Code 33 will set if voltage at 36VLR of DERM is detected within first 500 milliseconds after ignition is turned on, 3 cycles in a row.

History Code 33 will remain as a history code until codes are cleared using a Tech 1 Scan Tester.

DERM stores a History Code 33.

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

1. Checks whether code was set by short ignition cycles.
2. Checks whether DERM has set code falsely.
3. Test determines whether fault is a short to voltage on 36VLR circuit or a shorted steering diode.

Scheme 38

At TURN-ON, Diagnostic Energy Reserve Module (DERM) monitors voltage at SENSE LOW input (terminal A6) for 500 milliseconds. DERM expects voltage to be within a specific range of IGNITION 1 voltage before 36-Volt Loop Reserve (36VLR) output is charged. If IGNITION 1 circuit from splice to arming sensor is open, voltage at SENSE LOW input, terminal A6, will be less than a certain percentage of IGNITION 1 voltage and Code 34 will set.

Tested once during each ignition cycle at TURN-ON.

Code 34 will set if voltage at SENSE LOW input (terminal A6) is less than a certain percentage of IGNITION 1 voltage for 500 milliseconds and 36VLR is less than IGNITION 1 output voltage at TURN-ON.

To clear Code 34, ignition must be off long enough to ensure 36VLR supply voltage has fully discharged. Once 36VLR is discharged, DERM will again check Failure Conditions upon key on. Only if Failure Conditions are not present (no failure indicated) will current Code 34 be cleared.

DERM turns on INFLATABLE RESTRAINT indicator light.

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

1. Checks whether DERM has set code falsely.
2. Checks whether IGNITION 1 is available at arming sensor.
3. Determines whether fault is an open in arming sensor or an open between arming sensor and steering column.

Scheme 39

Code 35 is set when voltage at SENSE LOW input (terminal A6) is within a specific range of 36-Volt Loop Reserve (36VLR) output voltage for 500 milliseconds during CONTINUOUS MONITORING tests performed by Diagnostic Energy Reserve Module (DERM). CONTINUOUS MONITORING tests are performed by DERM after initial TURN-ON tests are completed and every 100 milliseconds while IGNITION 1 voltage is present at DERM. If a discriminating sensor is open, voltage at SENSE LOW input will increase due to increase in resistance of discriminating sensor section of deployment loop, and Code 35 will set.

Test Condition

Tested every 100 milliseconds during CONTINUOUS MONITORING.

Code 35 will set if voltage at SENSE LOW input (terminal A6) is within a specific range of 36VLR output voltage for 500 milliseconds.

Code 35 will clear if voltage at SENSE LOW input is within a specific range of 36VLR output voltage for 500 milliseconds.

DERM turns on INFLATABLE RESTRAINT indicator light.

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

1. Checks resistance of left forward discriminating sensor.
2. Checks for proper resistance of right forward discriminating sensor.
3. Checks for open in discriminating sensor interconnect circuit No. 349.
4. Checks for an open in left forward discriminating sensor ground circuit.
5. Checks for open in right forward discriminating sensor ground circuit.

Scheme 40

DERM measures deployment loop energy reserve voltage (36VLR) and ensures it reaches a certain voltage within 7 seconds after IGNITION 1 voltage is applied. If this voltage is not reached, Code 41 is set. DERM monitors 36VLR and checks that it remains above a certain voltage while IGNITION 1 voltage is present. If 36VLR falls below a certain voltage after initial charging, Code 42 is set. These codes indicate a fault internal to DERM or a short to ground or voltage between diode attached to terminal "B" or arming sensor and 36VLR output terminal A2.

Code 41 is tested each ignition cycle at TURN-ON. Code 42 is tested every 100 milliseconds during CONTINUOUS MONITORING.

Code 41 will set if 36VLR has not reached a certain voltage 7 seconds after TURN-ON. Code 42 will set if 36VLR is below a certain voltage after initial charging.

Current Code 41 will be cleared each time ignition is turned off. Code 42 will clear if 36VLR is greater than a certain voltage for 500 milliseconds after Code 42 has set.

DERM turns on INFLATABLE RESTRAINT indicator light.

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

1. Checks whether DERM has set code falsely.
2. Test determines whether fault is due to short in arming sensor or short from 36VLR circuit to voltage.

Scheme 41

DERM determines arming sensor is closed when a specific percentage of deployment loop voltage or more is present at SENSE HI input, terminal A7, and determines a discriminating sensor is closed when a specific percentage of deployment loop voltage or less is present at SENSOR LOW input, terminal A6. If both conditions are detected simultaneously, Code 51 is set.

Code 51 conditions are monitored whenever DERM is functioning properly.

Current Code 51 will set if DERM senses arming sensor and at least one discriminating sensor are closed simultaneously.

Current Code 51 can be cleared using a Tech 1 Scan Tester clear codes command; History Code 51 will remain in DERM thereafter.

DERM turns on INFLATABLE RESTRAINT indicator until current Code 51 is cleared.

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

1. Code 51, once detected, can be erased as a current code but will remain as an unerasable history code.
2. If inflator module has not deployed, Code 51 may have set falsely.
3. If Code 51 is current with no signs of frontal impact, code is falsely set.
4. Test checks for a DERM fault setting code falsely.
5. Test determines whether code was set inadvertently during diagnosis.
6. When an accident has occurred, perform indicated procedures to ensure SIR system is fully functional.

Scheme 42

When a vehicle accident of sufficient magnitude to set a Code 51 occurs, Diagnostic Energy Reserve Module (DERM) stores accident information in Electrically Erasable Programmable Read Only Memory (EEPROM). Code 52 is set when EEPROM has stored 4 simultaneously closed arming an discriminating sensor events (Code 51 settings).

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

Tested every 100 milliseconds during CONTINUOUS MONITORING.

Code 52 will set when EEPROM area reserved for accident data in DERM is detected to be full during CONTINUOUS MONITORING.

Code cannot be cleared.

INFLATABLE RESTRAINT indicator is turned on during all future ignition cycles.

Scheme 43

Diagnostic Energy Reserve Module (DERM) monitors ground driver (quad driver module) output by comparing output state to processor commanded state. Code 61 will set when commanded state does not match output state of ground driver. A possible cause for a Code 61 is an open or short to ground in FORCE LOW circuit.

Tested every 100 milliseconds during CONTINUOUS MONITORING.

Code 61 will set if voltage at SENSE LOW input is greater than 8 volts or feedback from ground driver does not agree with commanded state for 500 milliseconds.

Current Code 61 will be cleared each time ignition is turned off.

DERM attempts to turn on INFLATABLE RESTRAINT indicator light.

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

1. Checks for an open 100-ohm resistor in resistor module.
2. Checks for an open between resistor module and DERM on FORCE LOW circuit.

Scheme 44

Code 71 is an internal Diagnostic Energy Reserve Module (DERM) fault and will set if any of these conditions are detected

1. DERM power supply reserve voltage charge or discharge time fails.
2. DERM power supply reserve voltage is less than 13 volts or greater than 19.6 volts for 500 milliseconds.
3. DERM is unable to read from or write to Electrically Erasable Programmable Read Only Memory (EEPROM).
4. 36-Volt Loop Reserve (36VLR) is greater than 44 volts for 500 milliseconds.

Tested during TURN-ON and every 100 milliseconds during CONTINUOUS MONITORING.

Code 71 is set when an internal DERM fault is detected during TURN-ON or CONTINUOUS MONITORING.

Current Code 71 will clear if no internal DERM faults are detected for 500 milliseconds.

DERM turns on INFLATABLE RESTRAINT indicator light.

Scheme 45

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. Kit also contains a cross-hatched core crimp to ensure positive contact for low energy circuits.

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

If 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. Use sealed splices and crimping tool for these splices. To open wiring harness, remove tape as necessary. To avoid wire insulation damage, use a sewing seam ripper. Use instructions in kit for wire repair procedure.

TORQUE SPECIFICATIONS

TORQUE SPECIFICATIONS

Scheme 46

See also:
• PASSIVE RESTRAINT SYSTEM INSPECTION