Volkswagen Workshop Service and Repair Manuals

The airbag control unit (J234) is located behind the console on the tunnel. It is equipped with a fault memory. The self diagnosis connections are located behind the cover below the heating and ventilation controls.

The control unit detects faults in the airbag system and stores them in a permanent memory.

Faults which can be attributed to a temporary open circuit in the wiring or a loose contact, will also be stored. These faults will be displayed as sporadic faults "SP".

After the ignition is switched on, the airbag warning lamp (K75) comes on for about 4 seconds and then goes out again. If the lamp then flashes for further 15 seconds then this signals that the front passenger airbag is blocked.

• ◆ If the warning lamp (K75) does not go out after about 4 seconds, then the voltage supply to the airbag control unit (J234) is faulty. Interrogate fault memory .
• ◆ A fault is present if the warning lamp (K75) lights up again. Interrogate fault memory => Page 01-21.
• ◆ If the warning lamp (K75) flashes continuously then the control unit (J234) must be renewed.

Introduce self-diagnosis when starting fault finding.

The stored information must be interrogated with fault reader V.A.G 1551 and checked with test box VAS 5056 to find which components are defective.

The fault information displayed is used to refer to a fault table with notes on the possible causes for directed repair measures.

Connecting fault reader V.A.G 1551 and selecting functions (Interrogating unit version)

Check prerequisites:

• ◆ All fuses according to current flow diagram OK.
• ◆ Battery voltage at least 9 V.

• ‒ → Open ashtray, remove if necessary and slide cover for diagnostic connections to left -arrow-.
• ‒ With ignition switched off, connect fault reader V.A.G 1551 using diagnosis cable V.A.G 1551/3.

• ◆ Display will show the actual software version installed (will be shown briefly in display)

* Is displayed alternately.

Notes:

• ◆ If the display remains blank, check V.A.G 1551 voltage supply according to current flow diagram.

=> Current flow diagrams, Electrical fault finding and Fitting locations binder

• ◆ Additional operating information can be printed out depending on the programme by pressing the HELP key of V.A.G 1551.
• ◆ The ⇒key is used for advancing the programme sequence.
• ◆ The PRINT key is used for switching on the printer (warning lamp in key lights up).

Interrogate control unit version

• ‒ Switch on ignition.
• ‒ Press key -1- for "Rapid data transfer" mode.

• ‒ Press keys -1- and -5- (the address word of the vehicle system to be tested "Airbag" is entered with 15).

• ‒ Confirm entry with the Q key.

• ◆ Top line    Part No. of control unit                System designation                (AIRBAG VW3)                Version number
• ◆ Lower line    Code number                Dealership number1)

1)- Will be automatically stored in the control unit when entering the system.

• ‒ Press ⇒key.

Notes:

• ‒ After rectifying the possible causes of the fault, once again enter the address word 15 for "Airbag" and confirm with the Q key.

and then the following appears in the display:

List of selectable functions

Notes:

• ◆ A list of possible functions is printed out after pressing the HELP key.
• ◆ Do not select further functions, which can be printed out after pressing the HELP key.
• ◆ After the function is completed the V.A.G 1551 returns to the following start position:

Interrogating fault memory

• ‒ Press keys -0- and -2- (the function "Interrogate fault memory" is entered with 02).

• ‒ Press Print key
• ‒ Confirm entry with the Q key.

The stored faults are displayed and printed out one after the other.

• ‒ Enter fault table at fault printed out and rectify.

If something else is displayed:

=> Fault reader operating instructions

• ‒ End output (function 06) => Page 01-24.
• ‒ Switch off ignition and separate diagnostic connections.

Note:

If a fault is recognised:

• ◆ . Rectify fault
• ◆ 2. Erase fault memory (function 05).
• ◆ 3. Interrogate fault memory again (function 02).

Erasing fault memory

Prerequisites:

• ◆ Faults are rectified
• ◆ Fault memory interrogated again

• ‒ Press keys -0- and -5- (the function "Erase fault memory" is entered with 05).

• ‒ Confirm entry with the Q key.

• ‒ Press ⇒ key.

Notes:

End output

• ‒ Press keys -0- and -6- to end the output.

• ‒ Confirm entry with the Q key.

• ‒ Switch off ignition.
• ‒ Separate connectors to fault reader V.A.G 1551.

Fault table

Notes:

• ◆ The following table lists all the faults, with the corresponding 5-digit code numbers, that can be recognized by the airbag control unit -J234- and printed out by the V.A.G 1551.
• ◆ Fault codes appear only on print-out.
• ◆ Before replacing a component shown as faulty, check wiring and connections to the component as well as earth connections according to current flow diagram.
• ◆ Check all relay plate connections are seated securely.
• ◆ When repair has been carried out, the fault memory must always be interrogated again with the fault reader V.A.G 1551 and erased.
• ◆ In addition, the fault type may also appear in the fault table.

1)    The fault message will only be stored in the fault memory when the matching is activated.