DESCRIPTION & OPERATION
| WARNING | To avoid injury from accidental air bag deployment, read and carefully follow all WARNINGS and SERVICE PRECAUTIONS. |
The Supplemental Restraint System (SRS) is designed to provide increased accident protection for driver and passenger by deploying air bag(s) in a front-end collision. The SRS is designed to be used with 3-point safety belts. All models are equipped with driver-side and passenger-side air bags. Cabriolet models are also fitted with pyrotechnic seat belt tensioners.
Air bags will activate if vehicle is in a frontal collision at about 9-12 MPH. Air bags will inflate within 25-30 milliseconds. The main components of the SRS include driver-side air bag unit, passenger-side air bag unit, control unit (triggering unit), data link connector, spiral spring assembly (under steering wheel, in steering column) and AIRBAG indicator light. (Scheme 1)
Scheme 1
Air bag control unit is capable of system self-diagnostics. Air bag system components are monitored electrically and any interferences in operation can be detected. These interferences (faults) are then stored in air bag control unit memory. Air bag control unit memory differentiates between 12 types of faults. After diagnosis and servicing, fault memory can be erased.
SERVICING
Manufacturer recommends replacing main air bag system components (driver-side air bag unit, passenger-side air bag unit, spiral spring and control unit) every 15 years. Replacement year and month appear on a sticker located on driver-side B-pillar. Sticker must be updated when components are replaced.
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.
ADJUSTMENTS
Information is not available from manufacturer.
DEPLOYED AIR BAG
Deployed air bag modules can be disposed of like any other part. Handle air bag module using gloves, and wear safety glasses. Some control units contain a mercury switch and must be disposed of as hazardous material. Control units that have a Red identification label do not contain a mercury switch and can be disposed of as any other part.
UNDEPLOYED AIR BAG
Undeployed air bags must be deployed before disposal. 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.
Transportation of undeployed air bag modules is regulated by Department of Transportation (DOT) and most state governments. Special shipping procedures are required. A DOT exemption label must be attached to undeployed air bag being shipped. This DOT exemption label is included with replacement air bag. Use replacement air bag shipping box to return undeployed air bag. Repair shops should check with hazardous material section of their respective state governments for applicable shipping requirements.
SCRAPPED VEHICLE
| WARNING | Some vehicles that have to be scrapped may have an undeployed air bag. Undeployed air bag modules must not be disposed of at normal refuse locations. DO NOT deploy air bags inside vehicle. |
Information is not available from manufacturer.
REMOVAL & INSTALLATION
| WARNING | Failure to follow air bag service precautions may result in air bag deployment and personal injury. See SERVICE PRECAUTIONS . After component replacement, ensure proper system operation. See SYSTEM OPERATION CHECK . |
Removal
- Before proceeding, see «SERVICE PRECAUTIONS»(/audi/a4/b5-1994-1999/remont/airbag/#air-bag-restraint-system__service-precautions). Disable air bag system. See «DISABLING & ACTIVATING AIR BAG SYSTEM»(/audi/a4/b5-1994-1999/remont/airbag/#air-bag-restraint-system__disabling-activating-air-bag-system). Control unit is located behind center console. (Scheme 1) To remove center console, remove handbrake lever trim. Unclip cover and unscrew bolts. Unclip ashtray and unscrew nut. (Scheme 2) Apply handbrake lever and raise rear center console slightly.
- Disconnect front part of center console. Remove center console toward the front. Unclip cable for diagnostic cable from center console. Remove cover and bolt for front part of console. Remove trim in center of instrument panel. Remove heater controls. Unclip cover, unscrew nut and bolts. Disconnect center console from front and pull out to rear. (Scheme 3)
Scheme 2
Scheme 3
Installation
To install, reverse removal procedure and tighten control unit mounting nuts to specification. See TORQUE SPECIFICATIONS . Reactivate the air bag system and check AIRBAG indicator light to ensure system is functioning properly. See SYSTEM OPERATION CHECK .
- Before proceeding, see «SERVICE PRECAUTIONS»(/audi/a4/b5-1994-1999/remont/airbag/#air-bag-restraint-system__service-precautions). Disable air bag system. See «DISABLING & ACTIVATING AIR BAG SYSTEM»(/audi/a4/b5-1994-1999/remont/airbag/#air-bag-restraint-system__disabling-activating-air-bag-system). Driver-side air bag unit is located on steering wheel hub.
- Remove Torx T30 retaining screws from back of steering wheel. (Scheme 4) Disconnect connector from air bag unit and remove air bag from vehicle.
Scheme 4
To install, reverse removal procedure. When replacing, install and tighten Torx T30 screws to specification. See TORQUE SPECIFICATIONS . Reactivate air bag system. Check AIRBAG indicator light to ensure system is functioning properly. See SYSTEM OPERATION CHECK .
Before proceeding, see SERVICE PRECAUTIONS. Disable air bag system. See DISABLING & ACTIVATING AIR BAG SYSTEM. Passenger-side air bag unit is located above glove box. Remove glove box. Remove air bag unit Torx mounting bolt. (Scheme 5) Pull out air bag unit from instrument panel. Disconnect orange air bag pigtail connector, and remove air bag. Never disconnect Red connector on side of air bag module. If connection is loose, air bag must be replaced.
To install, reverse removal procedure. Always use a new bolt when replacing air bag. Be certain air bag pigtail does not get caught between instrument panel and air bag module. A short could result. Tighten air bag unit mounting bolt to specification. See TORQUE SPECIFICATIONS . Reactivate air bag system. Check AIRBAG indicator light to ensure system is functioning properly. See SYSTEM OPERATION CHECK .
Scheme 5
- Before proceeding, see «SERVICE PRECAUTIONS»(/audi/a4/b5-1994-1999/remont/airbag/#air-bag-restraint-system__service-precautions). Disable air bag system. See «DISABLING & ACTIVATING AIR BAG SYSTEM»(/audi/a4/b5-1994-1999/remont/airbag/#air-bag-restraint-system__disabling-activating-air-bag-system). Ensure front wheels are in straight-ahead position.
- Spiral spring is located under steering wheel. Remove driver-side air bag unit. See «DRIVER-SIDE AIR BAG UNIT»(/audi/a4/b5-1994-1999/remont/airbag/#air-bag-restraint-system) under REMOVAL & INSTALLATION. Remove steering wheel. See «STEERING WHEEL»(/audi/a4/b5-1994-1999/remont/airbag/#air-bag-restraint-system) under REMOVAL & INSTALLATION. Disconnect spiral spring electrical connector. Remove 4 Torx T20 retaining screws. Remove spiral spring. (Scheme 6) DO NOT turn or twist unit after removal.
Scheme 6
- Check spiral spring before installation with both ends disconnected. Using an ohmmeter, check resistance at spiral spring air bag unit connector terminal. (Scheme 7) Resistance should be less than 1 ohm. If resistance is not less than 1 ohm, replace spiral spring. Torque retaining bolts to 20 INCH Lbs. (2.3 N.m.).
- To install, reverse removal procedure. Ensure front wheels are in straight-ahead position. From central position, spiral spring must be able to turn approximately 3 1/2 turns in both directions. Reactivate air bag system. Ensure system is functioning properly. See «SYSTEM OPERATION CHECK»(/audi/a4/b5-1994-1999/remont/airbag/#air-bag-restraint-system__system-operation-check).
Before proceeding, see SERVICE PRECAUTIONS . Disable air bag system. See DISABLING & ACTIVATING AIR BAG SYSTEM . Turn front wheels to straight-ahead position. Remove driver-side air bag unit. See DRIVER-SIDE AIR BAG UNIT under REMOVAL & INSTALLATION. Remove steering wheel nut and spring washer. Mark steering wheel and shaft for installation reference. Remove steering wheel.
To install, reverse removal procedure. Tighten steering wheel nut to specification. See TORQUE SPECIFICATIONS . Reactivate air bag system. Check AIRBAG indicator light to ensure system is functioning properly. See SYSTEM OPERATION CHECK .
SYSTEM OPERATION CHECK
Turn ignition switch to ON position. AIRBAG indicator light should come on for about 4 seconds and then go out. If light flashes and then remains on, control unit has detected a system fault. See TESTING . If light does not glow, check bulb. If bulb is okay, perform diagnostics. See TESTING .
SERVICE PRECAUTIONS
Observe these precautions when working with air bag systems
- Before disconnecting battery cable(s) and disabling air bag system, obtain radio security code from vehicle owner.
- Before installing computer memory saver on vehicles with electronic radio lock, disconnect air bag voltage supply connector. See «DISABLING & ACTIVATING AIR BAG SYSTEM»(/audi/a4/b5-1994-1999/remont/airbag/#air-bag-restraint-system__disabling-activating-air-bag-system). (Scheme 1) Failure to do so may cause air bag activation.
- Disable air bag system before servicing any part of system. See «DISABLING & ACTIVATING AIR BAG SYSTEM»(/audi/a4/b5-1994-1999/remont/airbag/#air-bag-restraint-system__disabling-activating-air-bag-system).
- Because of critical operating requirements of system, DO NOT attempt to service any air bag system component.
- DO NOT leave air bag parts unattended. Install air bag parts in vehicle immediately after they are obtained.
- DO NOT use air bag components that have been dropped from heights of approximately 18" or higher.
- DO NOT allow chemical cleaners, oil, or grease to contact vinyl covering on air bag unit.
- DO NOT place stickers or covers on steering wheel.
- Disable SRS before performing electric welding on vehicle.
- SRS can only be tested using Diagnostic Tester (VAG 1551) and Adapter Test Harness (VAG 1551/1). DO NOT use Air Bag Tester (VAG 1619). Never use test light, ohmmeter or voltmeter to test air bag system, except when testing clockspring.
- DO NOT expose air bag unit to temperatures greater than 212°F (100°C).
DISABLING & ACTIVATING AIR BAG SYSTEM
- Before proceeding, see «SERVICE PRECAUTIONS»(/audi/a4/b5-1994-1999/remont/airbag/#air-bag-restraint-system__service-precautions) . To disable air bag system, disconnect and shield negative battery cable.
- To activate system, reconnect negative battery cable. Perform system operation check to ensure system is functioning properly. See «SYSTEM OPERATION CHECK»(/audi/a4/b5-1994-1999/remont/airbag/#air-bag-restraint-system__system-operation-check) .
WIRE REPAIR
Information is not available from manufacturer.
TORQUE SPECIFICATIONS
| Application | Ft. Lbs. (N.m) |
|---|---|
| Passenger-Side Air Bag Unit Mounting Bolt | 11 (15) |
| Steering Wheel Nut | 30 (40) |
| INCH Lbs. (N.m) | |
| Control Unit Mounting Nuts | 53 (6) |
| Driver-Side Air Bag Unit-To-Steering Wheel Screws | 89 (10) |
TORQUE SPECIFICATIONS
TESTING
| WARNING | Failure to follow air bag service precautions may result in air bag deployment and personal injury. See SERVICE PRECAUTIONS . After component replacement, ensure proper system operation. See SYSTEM OPERATION CHECK . |
Preliminary Steps
Ensure vehicle's electrical system is operating within normal voltage range. To ensure all faults are stored, allow vehicle to idle in Neutral with parking brake fully applied. Remove carpet from passenger side of vehicle to access diagnostic connectors.
Scheme 7
- To code a new unit from `as delivered' condition, the following procedure must be followed. Connect VAG 1551/1 as follows: Connect Black diagnostic connector (ground/voltage supply) to Black data link connector. (Scheme 7) Connect White diagnostic connector (carrying code transmission) to White data link connector. Blue diagnostic connector is not used during air bag diagnostics. Connect Diagnostic Cable Lead (VAG 1551/1) to Diagnostic Tester (VAG 1551).
- Switch on printer (control light on). Select rapid data transfer. Press button 1 and 5 to select airbag code 15. Confirm input with "Q" key. Use right arrow to scroll forward through program. RAPID DATA TRANSFER and SELECT FUNCTION appear on display. Press buttons to access coding. The following functions are possible: 02 - Interogate Diagnostic Trouble Code (DTC Memory). 05 - Erase DTC Memory. 06 - End Output. 07 - Code Control Module. 08 - Read Measuring Value Block.
| Measuring Value Block | Diagnostic Test Code | |
|---|---|---|
| Driver-Side Air Bag | ||
| 1111 | No Malfunction | |
| 0111 High Resistance | 00588 | |
| 1011 Low Resistance | 00588 | |
| 1101 Short to Ground | 00594 | |
| 1110 Short to Voltage | 00594 | |
| Passenger-Side Air Bag | ||
| 1111 | No Malfunction | |
| 0111 High Resistance | 00589 | |
| 1011 Low Resistance | 00589 | |
| 1101 Short to Ground | 00594 | |
| 1110 Short to Voltage | 00594 | |
| Driver-Side Seat Belt Tensioner | ||
| 1111 | No Malfunction | |
| 0111 High Resistance | 00654 | |
| 1011 Low Resistance | 00654 | |
| 1101 Short to Ground | 00654 | |
| 1110 Short to Voltage | 00654 | |
| Passenger-Side Seat Belt Tensioner | ||
| 1111 | No Malfunction | |
| 0111 High Resistance | 00655 | |
| 1011 Low Resistance | 00655 | |
| 1101 Short to Ground | 00655 | |
| 1110 Short to Voltage | 00655 | |
CONVERTING ERROR CODES
Printer Display
None.
Symptom
Air bag does not deploy.
Possible Cause
Alternator/voltage regulator defective. Weak or defective battery. Short in wiring.
Corrective Action
Repair or replace alternator/voltage regulator. Charge or replace battery. Locate and repair short in wiring.
Printer Display, N95
High resistance.
Driver-side air bag does not ignite.
Ignitor disconnected. Spiral spring defective. Driver-side air bag defective. Control unit defective.
Check and reconnect ignitor. Check spiral spring. Replace driver-side air bag unit. Replace control unit.
Low resistance.
Driver-side air bag does not ignite.
Open circuit. Spiral spring defective. Driver-side air bag defective. Control unit defective.
Locate and repair open circuit. Check spiral spring. Replace driver-side air bag. Replace control unit.
CODE 00588 - DIAGNOSTIC PROCEDURE
Check wiring from Air Bag control unit to warning lamp. Disconnect voltage supply. Remove air bag. Locate and disconnect 2-pin harness connector under steering column. Locate and disconnect air bag connector at control unit. Check resistance of each circuit in harness. If not approximately 0 ohms, replace harness.
Disconnect spiral spring 2-pin plugs at air bag module and steering column harness. Check from one pin of connector to the other. Perform test on both connectors to be positive spiral spring is functioning correctly. Spiral spring has a shorting bar inside harness side connector. Disable shorting bar by carefully holding one side away from terminal while testing. An erroneous reading will result if this is not done. Resistance should be infinite for both sides. If it is not, replace spiral spring. When testing, turn steering wheel from lock to lock. If spiral spring passes this test, proceed to next check.
Check resistance from steering wheel connector to harness connector. Check each circuit independently. Resistance should be approximately 0 ohms. If it is not, replace spiral spring. Turn steering wheel from lock to lock while testing.
Clean all terminals carefully and apply Stabilant 22A or equivalent to steering column harness connector. Reconnect all disconnected plugs and replace cover panels. Clear DTC code memory. Road test vehicle for minimum of 10 miles. If DTC reappears, replace spiral spring.
If DTC reappears after spiral spring replacement, change driver-side air bag module.
Printer Display, N131
High resistance.
No. 1 ignitor for passenger-side air bag does not ignite.
Ignitor disconnected. Passenger-side air bag defective. Control unit defective.
Reconnect ignitor. Replace passenger-side air bag. Replace control unit.
Low resistance.
No. 1 ignitor for passenger-side air bag does not ignite.
Open circuit. Passenger-side air bag defective. Control unit defective.
Locate and repair open circuit. Replace passenger-side air bag. Replace control unit.
Printer Display, N132
High resistance.
No. 2 ignitor for passenger-side air bag does not ignite.
Ignitor disconnected. Passenger-side air bag defective. Control unit defective.
Reconnect ignitor. Replace passenger-side air bag. Replace control unit.
Low resistance.
No. 2 ignitor for passenger-side air bag does not ignite.
Open circuit. Passenger-side air bag defective. Control unit defective.
Locate and repair open circuit. Replace passenger-side air bag. Replace control unit.
None.
Ignitor for air bag does not ignite.
Air bag circuit wiring damaged or control unit defective.
Locate and repair damaged wiring. Replace control unit.
None.
Ignitor for air bag does not ignite.
Air bag circuit wiring damaged. Spiral spring defective. Air bag unit defective. Control unit defective.
Locate and repair damaged wiring. Check spiral spring. Replace air bag unit. Replace control unit.
None.
Front impact.
Air bags deployed.
Replace control unit, air bag units and spiral spring. Also check remaining SRS components for damage and replace as necessary.
None.
Indicator light stays on constantly or is inoperative.
Defective bulb. Disconnected or damaged wiring. Instrument panel insert defective. Control unit defective.
Replace indicator light bulb. Check and repair indicator light circuit wiring. Repair instrument panel insert. Replace control unit.
CODE 01025 - DIAGNOSTIC PROCEDURE
Check wiring from Air Bag control unit to warning lamp. Disconnect voltage supply, and control unit connectors and warning lamp wiring from instrument cluster. Check resistance from warning lamp socket to ground. Check each side independently. Resistance should be infinite for both. Reconnect all removed plugs and switch ignition on. Ensure warning lamp is fully seated in socket and wiring connections are tight. Check warning lamp relay in auxiliary relay panel. If warning lamp is still operating incorrectly, replace warning lamp relay and retest. Clear DTC code memory when fault is corrected.
None.
Air bag system does not function.
Defective control unit.
Replace control unit.
