Audi A4 Owners & Service Manuals

Audi A4: Safety Precautions

Safety Precautions when Working on Vehicles with Start/Stop System

There is a risk of injury due to the engine starting unexpectedly.

The engine can start unexpectedly on vehicles with an activated Start/Stop System. A message in the instrument cluster indicates whether the Start/Stop System is activated.

- Deactivate the Start/Stop System: Switch off the ignition.

Safety Precautions when Working with Pyrotechnic Components


Pyrotechnic components include:

  • Airbag units
  • Belt tensioners
  • Seat belt force limiter (depending on vehicle equipment)
  • Battery cut-out elements (depending on vehicle equipment)


  • Testing, assembly, and repair work may only be performed by qualified personnel.
  • There is no change interval for airbag units.
  • Never test with a test light, volt meter or ohm meter.
  • The pyrotechnic components may be checked only when they are installed and with a Vehicle Diagnostic Tester approved by the manufacturer.
  • When working on the airbag system (pyrotechnic components, Airbag Control Module -J234-, wiring), the battery ground cable must be disconnected when the ignition is SWITCHED ON. Then cover the negative terminal.
  • Wait for 10 seconds after disconnecting the battery.
  • The ignition must be SWITCHED ON when connecting the battery. Nobody should be inside the vehicle when doing this. Exception: Vehicles with a battery inside the passenger compartment.
  • If the ignition is not switched on after the battery is reconnected - the indicator lamps in the instrument cluster do not turn on - the ignition (key/button) may be switched on while sitting in the driver seat with the seat all the way back.
  • Follow the steps after connecting the battery. Refer to → Electrical Equipment; Rep. Gr.27; Battery; Battery, Disconnecting and Connecting.
  • The technician must discharge static electricity before handling pyrotechnic components for the restraint system, For example, before disconnecting the connector. Touching grounded metal parts will discharge the static electricity, For example by touching the door striker.
  • Wash hands after touching ignited restraint system pyrotechnic components.
  • Pyrotechnic components may not be opened nor repaired; always use new parts (risk of injury).
  • Pyrotechnic components that have fallen onto a hard surface or show signs of damage must not be installed in the vehicle.
  • Pyrotechnic components should be installed immediately upon removal from shipping package.
  • If the procedure must be stopped for awhile, put the pyrotechnic component back into its shipping package.
  • It is not permitted to leave a pyrotechnic component out unattended.
  • When connecting restraint system pyrotechnic components, only the person performing the work should be in the vehicle.
  • Do not use any grease, cleaning solutions or similar substance on pyrotechnic components.
  • Replace the airbag unit if any contaminants such as oil, grease, paint, dye or solvents have penetrated the fabric.
  • Pyrotechnic components must not be exposed to temperatures over 100 ºC (212 ºF), even for a short time.

Special Information regarding driver and front passenger airbags

  • Store the driver and front passenger airbag units in the uninstalled state so that the cushioned side faces upward.

When replacing airbag units, the following sequence must be followed exactly:

1 - Remove the old airbag unit and store with the cushion side facing up.

2 - Remove the new airbag unit from the shipping packaging and store it with the cushion side facing up.

3 - Place the old airbag unit in the shipping packaging immediately.

4 - Install the new airbag unit in the vehicle.

Special Information regarding Belt Tensioners

  • Use extreme care when removing and installing belt tensioner units. Improper handling of belt tensioner units is very dangerous and could result in serious personal injury.
  • Belt tensioner units that are mechanically damaged (dents, cracks) must always be replaced.
  • The open end of the belt tensioner should never be pointed at anyone.
  • When connecting a belt tensioner, all mechanical parts, including those in the three-point seat belt, must be secured correctly. If it is not possible to connect the belt tensioner because of insufficient space, the seat belt webbing must be rolled up completely prior to connection. In this case there is no increased safety risk, if all other safety instructions are followed. This particularly includes the notes regarding the disconnection of the battery and the static discharging of the technician prior to connecting the belt tensioner.
  • Even after a crash, it is possible that the belt tensioner ignited, but the seat belt force limiter did NOT. Treat these components as if they had not ignited.

Airbag, Belt Tensioner and Battery Cut-Out Units, Storing, Transporting and Disposing (Pyrotechnic Components)

  • Storage must conform to national legislation.
  • Transport must conform to national and international guidelines, whereby packaging, identification and shipping documents are regulated to the greatest detail.
  • Undeployed pyrotechnic components must be disposed of in an orderly manner in their original packaging, that conforms to national legislation. Contact the importer for questions.
  • Only pyrotechnic components, which have been ignited completely, may be disposed in industrial waste.


  • This does not apply to belt tensioners that function according to the Wankel pretensioner principle. These are to be treated like undeployed pyrotechnic components (such as airbags, seat belts, pyrotechnic battery cut-out elements).
  • Background: Workshop equipment cannot determine if belt tensioners have deployed all pyrotechnic materials according to the Wankel pretensioner principle.


     Additional Safety Precautions for Airbag Control Module

      WARNING After every removal and installation of the Airbag Control Module -J234-, the "inertial sensor basic setting" must be performed. If the Airbag Control Module -J234- is replaced w

     Restraint System Pyrotechnic, Electric and Mechanical Components, Replacing After a Collision

    Special tools and workshop equipment required Vehicle Diagnostic Tester The airbag control module must be replaced If the display "Control module faulty" appears after checking the DTC memory A

     Seat Belts, Checking

      WARNING The seat belt system must be inspected systematically after every accident. If damage is determined at any inspection point, the customer must be informed that it is necessary to r


     Plenum Chamber Bulkhead, Removing and Installing

    Removing - Remove the engine cover. Refer to → Engine Mechanical; Rep. Gr.10; Engine Cover; Engine Cover, Removing and Installing. - For vehicles that have a pass-through for the coolant lines through the plenum chamber bulkhead, drain the coolant. Refer to → Eng

     Exterior Rearview Mirror

    Overview - Exterior Rearview Mirror 1 -  Mirror Trim 2 -  Bolt 1.5 Nm 3 -  Mirror Adjusting Unit Removing and installing. Refer to → Chapter "Mirror Adjusting Unit, Removing and Installing". 4 -  Bolt Tightening specification. Refer to → 

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