The airbag only deploys as a result of severe impact from a line of 30° from center of the grille (i.e., a front impact). Side- or rear-only impacts will not deploy the airbag.
The lights will illuminate because:
The pre-determined service time has passed
There is a fault in the airbag system (usually with the crash sensors and/or clock spring)
Work was done to the electrical system without first disabling the airbag system
When the airbag lights are illuminated, it means the control unit has detected a problem with the system and, in turn, shuts the airbag system off; i.e., the airbag will NOT deploy in an accident if the lights are lit. If disconnecting the battery for one hour does not reset the system (thereby turning off the lights) the car must be taken to your local Volkswagen dealer for servicing if you want/need a working airbag system (or follow the procedures in the next section).
The left indicator light is the readiness indicator (incandescent bulb) and will light for approximately 5 seconds at start-up. The right indicator light (LED bulb) monitors the electronic control/monitoring unit, the igniter, the sensor circuits and system warning.
The system must be inspected if:
The left indicator light does not come on when the ignition is switched on
The left indicator light does not go out approximately 5 seconds after the ignition is switched on
The left or right indicator light comes on or flickers while driving
Diagnosing the System / Reading & Clearing Fault Codes
There is a diagnostic blink sequence that can be read from a home-brewed diagnostic connector, or a simple jumper wire. To obtain the diagnostic blink code from the Cabriolet airbag control unit:
Make sure the ignition switch is off.
Using a jumper wire (solid, not stranded), ground pin #1 (the one with the green wire) of the red airbag diagnostic connector.
While pin #1 is grounded, turn the ignition switch to the battery-on position (do not start engine).
Keep pin #1 grounded for about 3 seconds, then disconnect from ground.
The airbag diagnostic light in the cluster should now blink in the following fashion: The light will glow for about 3 seconds, turn off, then blink the code out in 4 distinct digit groups with a pause in between each digit. The process will repeat. Tap here for an example.
Move on to the next code (if there is one): As soon as the long blink comes on again, simply reconnect the jumper wire to ground for a couple of seconds, and then disconnect it. The next code will blink like the first. Tap here for another example.
Note: There can also be a 3-digit blink code (any 4-digit code ending in 0 will blink in a 3-digit sequence).
Eventually you will see the following pattern: long blink *pause* blink blink blink *pause* long blink *pause* blink blink blink, repeatedly. This means you are at the end of the fault code sequence (i.e. all fault codes have been identified). Tap here for an example.
Clear the fault codes: Ground pin 1 for 10 seconds, disconnect jumper, then switch off the ignition switch.
Additional info: "You go about clearing the 4-digit codes normally until you get to what seems to be a THREE digit code of 111. You must then ground the connection for ten seconds or more until the left lamp goes solid on. This is extremely important. Once you get to this stage, release the ground and turn off the ignition. WAIT one minute with the key out, then put the key in and IMMEDIATELY start the car (don't turn the key to the on position and then start, just turn the key immediately to crank and start the car). The left light will blink and eventually go off. The right light, should be out after starting." ~Rob
Current/existing fault codes cannot be erased until the problem is fixed. The instrument cluster warning lights will remain lit.
Thanks to "dandydanny" and "redcorradoguy" of VWvortex.com for this info!
Tap here for the list of fault codes and their definitions (the code reading procedure above is on the last page).
Thanks to "dandydanny" of VWvortex.com for this info!
Servicing the System
The airbag system in these cars can only be serviced by a Volkswagen dealer, unless an independent shop happens to have the proper tools, including the VAG-1551 scan tool (with OBD I interface and an old, outdated program card installed). No other scan tool can be used with the Cabriolet airbag system.
A replacement airbag costs $1,400 (as of April, 2008), a new control unit costs around $1,200 (as of June, 2008), and the remaining components total about another $1,200 (as of June, 2008); those costs do not include tax nor installation. Yes, you read that right: Over three thousand American dollars to replace the airbag system; that's more than what many of these cars are worth. Repairing/replacing the airbag system in these cars is now essentially cost-prohibitive. Furthermore, the airbag system is now long past its 10-year lifespan. The components that deploy the airbag degrade over time, eventually rendering the airbag useless as a safety device. Even if the system fault codes are pulled, the system is repaired and reset, there is no guarantee that the airbag will deploy in a front-end accident. Additionally, the system can be reset one day only to have the lights come back on a few days later (this is indicative of a faulty system that needs replacing, not repairing). On the flip side, there is a small possibility of the airbag deploying on its own, at any given time.
What does all of this mean? You are simply better off removing the airbag system from the car than repairing it, but the choice (and wallet) is yours. If the control unit is found to be faulty and you wish to replace it, whether it's new or used, be certain that the control unit comes with its factory-installed wire and test plug harness (#6 in the diagram). If it doesn't, it is very much a useless part.
Disabling the System / Turning the Warning Lights Off
If the warning lights are on and/or you have no desire to have a functioning airbag, the airbag system can be disabled and the lights turned out using the following method (warning: disable the airbag system at your own risk!).
Disconnect the battery.
Locate the airbag harness connector near the relay panel under the dash.
Pry up the orange retaining bar and pull apart the wire harness connectors (#6 in the diagram). On the smaller connector, find the two black wires that connect to T6/3 and T6/4 and cut them.
Splice those now-four black wires together.
Leave the harness disconnected. (System restoration is as simple as reconnecting the controller harness).
Caution: The above method disables the airbag system, it does not deactivate the airbag system! In theory, once the lights come on they remain on in the control unit's memory until the system is reset. Technically, this means that the airbag system is off and will not deploy. However, despite this, there is still a slim possibility of the airbag deploying if the circumstances are just right. Follow the above procedures at your own risk! The only way to permanently rid your car of the airbag is to remove it (and dispose of it properly; see video #4 above).
The above method and photos are provided by "tolusina" of VWvortex.com; he nor I will be held responsible should anything go wrong during and/or after you follow the above airbag system disabling procedures!
Replacing the Steering Wheel
To permanently rid your Cabriolet of the airbag &/or to replace the steering wheel:
Disconnect the battery and wait 20 minutes.
Disconnect the wire harness connectors (#6 in the diagram) located below the fuse/relay panel. On the smaller connector, find the two black wires that connect to T6/3 and T6/4 and splice them together (splice them without cutting, or cut both wires and splice all four ends together and system restoration is as simple as reconnecting the controller harness). Tap here for a picture example.
Remove the airbag (Allen screw on each side), steering wheel, airbag spring clock, steering column shaft, and turn signal/wiper stalk (Tap here to see the components you need to remove, and watch video #3 in the servicing section up above).
Install non-airbag steering wheel, steering column shaft from a 1975-1989 A1 chassis Volkswagen, and turn signal/wiper stalk from a 1975-1989 A1 chassis Volkswagen. You will also need to splice the horn contact wire(s).
For further discussion on the airbag system and its removal, Tap here.
The 1990 model year Cabriolets had a recall issued on their airbag systems. It is recall #91V215000. Visit the Recalls page for more information.