Air Bag Restraint System Audi A6 C4

DESCRIPTION & OPERATION

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.

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.

Audi 90 is equipped with airbag III, an expanded system with more comprehensive diagnostic capabilities.

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

Information is not available from manufacturer.

REMOVAL & INSTALLATION

Removal

1. Before proceeding, see «SERVICE PRECAUTIONS»(/audi/a6/c4-1994-1997/remont/airbag/#air-bag-restraint-system__service-precautions). Disable air bag system. See «DISABLING & ACTIVATING AIR BAG SYSTEM»(/audi/a6/c4-1994-1997/remont/airbag/#air-bag-restraint-system). Control unit is located behind center console. (Scheme 1) To remove center console, remove console kick panels. Remove shift handle.
2. Unclip cigarette lighter trim and remove screws under trim. Remove rear air duct from the console. Pull up on the parking brake handle. Using a screwdriver, carefully pry off parking brake handle and remove radio. Pull the center console toward rear and disconnect the A/C control panel.
3. Disconnect all connectors necessary to remove console. Remove center console. Remove 3 control unit mounting nuts. Disconnect control unit connector. Remove control unit. (Scheme 2)

Scheme 2

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 TESTING - SYSTEM OPERATION CHECK .

1. Before proceeding, see «SERVICE PRECAUTIONS»(/audi/a6/c4-1994-1997/remont/airbag/#air-bag-restraint-system__service-precautions). Disable air bag system. See «DISABLING & ACTIVATING AIR BAG SYSTEM»(/audi/a6/c4-1994-1997/remont/airbag/#air-bag-restraint-system). Driver-side air bag unit is located on steering wheel hub.
2. Remove Torx head retaining screws on rear of steering wheel. (Scheme 2) Lift off air bag unit from steering wheel, and tilt air bag unit downward. Disconnect wiring connector from air bag unit.

To install, reverse removal procedure. Tighten air bag unit screws to specification. See TORQUE SPECIFICATIONS . Reactivate air bag system. Check AIRBAG indicator light to ensure system is functioning properly. See TESTING - SYSTEM OPERATION CHECK .

Scheme 3

1. Before proceeding, see «SERVICE PRECAUTIONS»(/audi/a6/c4-1994-1997/remont/airbag/#air-bag-restraint-system__service-precautions). Disable air bag system. See «DISABLING & ACTIVATING AIR BAG SYSTEM»(/audi/a6/c4-1994-1997/remont/airbag/#air-bag-restraint-system). Passenger-side air bag unit is located above glove box. Remove instrument panel upper cover. (Scheme 3)
2. Remove lower trim panel from instrument panel. Remove glove box. Remove 6-mm nut located behind right air vents. Remove air bag unit mounting bolt. (Scheme 4) Using a screwdriver, pry up on air bag unit bracket. (Scheme 5) Disconnect air bag unit connector, and remove air bag.

Scheme 4

Scheme 5

To install, reverse removal procedure. 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 TESTING - SYSTEM OPERATION CHECK .

1. Before proceeding, see «SERVICE PRECAUTIONS»(/audi/a6/c4-1994-1997/remont/airbag/#air-bag-restraint-system__service-precautions). Disable air bag system. See «DISABLING & ACTIVATING AIR BAG SYSTEM»(/audi/a6/c4-1994-1997/remont/airbag/#air-bag-restraint-system). Ensure front wheels are in straight-ahead position.
2. Spiral spring is located under steering wheel. Remove driver-side air bag unit. See «DRIVER-SIDE AIR BAG UNIT»(/audi/a6/c4-1994-1997/remont/airbag/#air-bag-restraint-system). Remove steering wheel. See «STEERING WHEEL»(/audi/a6/c4-1994-1997/remont/airbag/#air-bag-restraint-system). Disconnect horn bracket from steering column. Remove 5 spiral spring retaining screws. Disconnect spiral spring electrical connector, and remove spiral spring. (Scheme 6) DO NOT turn or twist unit after removal.

Scheme 6

Scheme 7

1. 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 0-1 ohm. If resistance is not 0-1 ohm, replace spiral spring.
2. To install, reverse removal procedure. Ensure front wheels are in straight-ahead position. Reactivate air bag system. Ensure system is functioning properly. See «TESTING - SYSTEM OPERATION CHECK»(/audi/a6/c4-1994-1997/remont/airbag/#air-bag-restraint-system__testing-system-operation-check).

SEAT BELT TENSIONERS

Information is not available from manufacturer.

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 . 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 TESTING - SYSTEM OPERATION CHECK .

TESTING - SYSTEM OPERATION CHECK

Turn ignition switch to ON position. AIRBAG indicator light should come on for about 10 seconds and then go out. If light flashes and then remains on, control unit has detected a system fault. See DIAGNOSIS . If light does not glow, check bulb. If bulb is okay, perform diagnostics. See DIAGNOSIS .

SERVICE PRECAUTIONS

Observe these precautions when working with air bag systems

1. Before disconnecting battery cable(s) and disabling air bag system, obtain radio security code from vehicle owner.
2. Before installing computer memory saver on vehicles with electronic radio lock, disconnect air bag voltage supply connector. See «DISABLING & ACTIVATING AIR BAG SYSTEM»(/audi/a6/c4-1994-1997/remont/airbag/#air-bag-restraint-system). (Scheme 1) Failure to do so may cause air bag activation.
3. Disable air bag system before servicing any air bag system or steering column component. See «DISABLING & ACTIVATING AIR BAG SYSTEM»(/audi/a6/c4-1994-1997/remont/airbag/#air-bag-restraint-system).
4. Because of critical operating requirements of system, DO NOT attempt to service any air bag system component.
5. DO NOT leave air bag parts unattended. Install air bag parts in vehicle immediately after they are obtained.
6. DO NOT use air bag components that have been dropped from heights of approximately 18" or higher.
7. DO NOT allow chemical cleaners, oil, or grease to contact vinyl covering on air bag unit.
8. DO NOT place stickers or covers on steering wheel.
9. Disable SRS before performing electric welding on vehicle.
10. 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.
11. DO NOT expose air bag unit to temperatures greater than 212°F (100°C).

Scheme 8

1. Before proceeding, see «SERVICE PRECAUTIONS»(/audi/a6/c4-1994-1997/remont/airbag/#air-bag-restraint-system__service-precautions). To disable air bag system, disconnect and shield negative battery cable. Disconnect voltage supply Red connector. On all models, connector is located in passenger-side footwell, above electronic box (marked with a warning tag). (Scheme 8)
2. To activate system, reconnect negative battery cable and voltage supply connector. Perform system operation check to ensure system is functioning properly. See «TESTING - SYSTEM OPERATION CHECK»(/audi/a6/c4-1994-1997/remont/airbag/#air-bag-restraint-system__testing-system-operation-check).

WIRE REPAIR

Information is not available from manufacturer.

TESTING

Preliminary Steps

Ensure vehicle's electrical system is operating within normal voltage range. Remove carpet from passenger side of vehicle to access diagnostic connectors.

Scheme 9

1. 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 9) 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).
2. Select rapid data transfer. Input address word 15 to access airbag III. Enter input with "Q" key. Use right arrow to scroll forward until RAPID DATA TRANSFER and SELECT FUNCTION appear on display. Press buttons "0" and "7" to access coding. Display should show RAPID DATA TRANSFER AND 07 CODE CONTROL MODULE.
3. Enter input with "Q" key. Display will now show CODING CONTROL MODULE and INPUT CODE NUMBER. Enter 00127 to code control unit. Enter input with "Q" key. Display should show 8A0959655C AIRBAG III AUDI D00 on first line and CODE 00127 06812 on second line. Use right arrow to access function mode.
4. Display will now show RAPID DATA TRANSFER and SELECT FUNCTION. Input "0" and "6" to access basic function mode when prompted. Display should now show RAPID DATA TRANSFER and 06 END OUTPUT. Enter input with "Q" key and coding is complete.

DIAGNOSIS

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.

Connecting Diagnostic Tester (VAG 1551)

1. Turn ignition switch to OFF position. Connect branched end of VAG 1551/1 to vehicle's Data Link Connector (DLC), located on passenger-side fuse/relay panel. Connect VAG 1551/1 as follows: Connect Black diagnostic connector (ground/voltage supply) to Black data link connector. (Scheme 9) 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).
2. Watch display readout. Operating modes "1" and "2" should appear alternately. If no display appears, check fuse No. 4. If fuse is okay, check voltage supply to VAG 1551. Minimum battery voltage of 10 volts is needed. Recharge battery as necessary.

Accessing VAG 1551 Fault Memory

1. If additional operating instructions are needed, press HELP key. To advance through program sequence, press arrow key. Press PRINT key for a complete printout of functions. Press "1" key to access RAPID DATA TRANSFER operating mode. Turn ignition switch to ON position. Press "1" and "5" keys to insert address word AIRBAG. Press "Q" key to enter data. After about 5 seconds, air bag control unit serial number should appear on display. If air bag voltage supply connector is not connected, CONTROL MODULE DOES NOT ANSWER will appear on display. Connect voltage supply connector if necessary.
2. If message AIRBAG CONTROL UNIT DOES NOT ANSWER appears on screen, press HELP key for printout of possible causes. Correct any problems before proceeding. Press "1" and "5" keys again and insert address word AIRBAG. Press "Q" key again to enter data.
3. Press right arrow key. RAPID DATA TRANSFER and SELECT FUNCTION should display on screen. Press "0" and "2" keys to access fault memory. Press "Q" key to enter data. Number of faults stored (if any) will appear on screen. NOTE: If fault is intermittent or fault memory is not cleared after malfunction is corrected, "/SP" will appear on right side of VAG 1551 screen.
4. Press right arrow key. Stored faults will be displayed and printed out. After last fault is displayed, press right arrow key again. Message RAPID DATA TRANSFER and SELECT FUNCTION should appear on screen. Diagnose and correct air bag system faults as necessary. See «TESTING - DIAGNOSTIC»(/audi/a6/c4-1994-1997/remont/airbag/#air-bag-restraint-system) .

Erasing Fault Memory

Access fault memory by pressing "0" and "2" keys. Press right arrow key. RAPID DATA TRANSFER and SELECT FUNCTION should appear on screen. Press "0" and "5" keys to select ERASE FAULT MEMORY. Press "Q" key to enter data. FAULT MEMORY ERASED will appear on screen.

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.

TORQUE SPECIFICATIONS

TORQUE SPECIFICATIONS

WIRING DIAGRAM

Information is not available from manufacturer.

See also:
• PASSIVE RESTRAINT SYSTEM INSPECTION
• SERVICE PRECAUTIONS
• TESTING - SYSTEM OPERATION CHECK
• DISABLING & ACTIVATING AIR BAG SYSTEM
• DIAGNOSIS