To add to my story, if you want to replace the module yourself, which will prove if either I or your mechanic is correct, you can do this yourself. You do not need to disconnect the battery, although, for liability reasons, it is specified in the service manual to do so. My coworkers an I have replaced hundreds of clock springs and never had a problem. Every electrical connector in the squib circuit is bright yellow. They will have more interlocking tabs than normal, their pins are gold-plated, and most importantly, a shorting bar touches the two terminals together anytime a connector is pulled apart.
A nine volt transistor battery is more than sufficient to pop an air bag for demonstration purposes. When sliding your butt across the seat, if you develop and feel a static electric shock, that is at least 3,000 volts. THAT'S what we worry about accidentally popping an air bag if we aren't careful. As long as the shorting bars are not tampered with, you can toss the bags around like a football and they won't pop.
The same shorting bars exist in the air bag connector, the squib connector at the base of the steering column or under the clock spring, and the connector at the module. All those safety devices are useless when the clock spring wires break. That leaves an open circuit that is subject to static electricity. The air bag assembly will become perfectly safe to handle when its connector is unplugged. That activates its shorting bar in the connector.
Basically, turn the ignition switch off, wait two minutes for the storage capacitors to discharge, (just a little extra precaution), unplug all the connectors, plug the new module in, and be sure to bolt it into the same bracket in the same orientation. Angle is critical for it to only pop above the design speed. You don't want it to pop to protect you from bumping into a shopping cart in the parking lot at 5 mph! :)
With the new (or old) module, watch the red warning light very closely when you turn on the ignition switch. It will light for the seven second self-test, then, if it continues to stay on steady, the self-test never completed. That is indeed a module problem. If the light blinks off for a fraction of a second, then comes right back on, the self-test completed and passed, then a problem was detected in the circuitry other than the module.
Also, be aware there are two different fused power circuits for the module. That's required so if the fuse blows for the module, there is a second backup power source to turn on the warning light. Many drivers are not in tune enough with the normal operation of their vehicles to watch for or interpret the light during the seven second self-test, and they wouldn't notice the light never turning on.
On minivans, one of those two fused circuits is for the rear wiper. The purpose for doing that is in case the rear wiper motor shorts rendering that safety system inoperable, you might never notice until you need it. The blown fuse will be evident by the air bag light telling the customer to get the vehicle serviced. Don't overlook a blown fuse.
Wednesday, March 3rd, 2010 AT 9:18 AM