Take airbag light problem to the dealer

  • Article by: PAUL BRAND , Star Tribune
  • Updated: February 4, 2009 - 5:28 PM

Q I am a 78-year-old woman with a 2004 Saab 9-3 that has fewer than 20,000 miles. About two months ago I began to get an intermittent display: "Airbag failure contact service." I took the car to my local mechanic and was told the display would have to be on in order to try to diagnose the problem and that I should call the dealer.

The dealership said that this was not a problem for which it could consult a computer, and I would need to bring the car and leave it. I'd need to rent a car, and because the display comes on very erratically, lasts only for about 10 seconds to 2 or 3 minutes, I have no faith that it would come on while the car is in the shop. When the display is on, it is a distraction, and there are no workable airbags at those moments. It's hard for me to believe that this is the only way to diagnose a safety problem in a nearly new car.

What should I do?

A The restraint system fault that triggers the "Airbag" warning light does not have to be on at the time of diagnosis. The fault code should be stored in the airbag control module's memory and can be read by a diagnostic scan tool plugged in to the vehicle's diagnostic link. This is why you must take the vehicle to the shop. Because the dealer has both the generic scan tool as well as the proprietary Saab diagnostic equipment, I'd suggest taking your vehicle to the dealer.

My best guess -- without sophisticated diagnostic tools it's just a guess -- is that there's a problem with the "clock-spring" assembly in the hub of the steering wheel. This mechanism provides a continuous electrical connection to the airbag while the steering wheel is turned as you drive the vehicle. An intermittent loss of continuity through the clock spring could cause the "Airbag" warning light to illuminate.

Q Where is the temperature sensor for the outside temperature display on the dashboard for cars like my 2007 Subaru? It is never exactly the temperature I hear on the radio or displayed one of those time-and-temperature clocks. If the sensor is under the hood someplace, what keeps it from being affected by the warming of the motor? And if it's outside the engine compartment, what keeps it from registering a colder temperature when the car is in motion? Riding a bike in zero degrees feels colder than standing still at that temperature.

A Interesting question. First, automobiles and their components do not "feel" windchill, so they never can be colder than ambient air temperature. Wind or vehicle motion can speed the dissipation of heat from a component, but can't cool it to below ambient temperature.

Many vehicles have the outside ambient-air temperature sensor mounted in a side mirror housing, but with today's heated mirrors, many vehicles like your Subaru have the sensor mounted near the front of the air/radiator opening where it's not influenced by engine compartment temperatures.

Why does the vehicle display vary from nearby temperature displays? Direct sunlight, heat reflecting off the road or exhaust from other vehicles might be a factor, but who said the temperature on the roadside display is accurate?

GOT QUESTIONS?

Write to Paul Brand, Star Tribune, 425 Portland Av. S., Minneapolis, MN 55488 or paulbrand@startribune. com. Please explain the problem in detail and include a daytime phone number. It isn't always possible to send a personal reply.

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