, Gloucester, MA


June 11, 2013

Why does air bag light turn on with no one in seat?

Q: I have a question regarding my 2005 Mercury Montego. My passenger-side air bag light turns on with nobody sitting in the seat. The light is supposed to turn on if a child is sitting in the front but does not weigh enough for the air bag to come on. But if an adult sits in the passenger seat, the air bag shut-off light is NOT lit as it should be. This just started today and never happened before. The vehicle has about 44,000 miles and runs perfectly. I did run over a speed bump moving fast the other day. Could this have caused the problem? Would it take a week for the light to come on?

A: This could be a very serious problem. The calibration of the seat could be way off. Or you could simply have an instrument cluster problem, which happens to be extremely common for your car. Before you get into major repairs, here is how I feel you should handle this problem, unless you want to go to the dealership.

Seek out a repair shop that uses a full-fledged scanner, not just a code reader. Read and record all codes in all modes. There are several computers in your car that need to be read, and a small code reader just won’t do it. After the codes are read and recorded, turn off the key and disconnect the negative battery cable for around two minutes. Reconnect the battery and start your car, and you may see that all is well. If the air bag light now works properly but you have a check engine light, simply clear the codes with a code eraser.

If all is well, you just dodged an expensive bullet.

If the problem is still present, a repair shop with a full Ford scanner, along with a skilled technician who is well-versed in Ford engineering, will be able to diagnose your problem, calibrate your seat and even update your computer with the latest software. If all the above work is done, you can expect to spend $200 to $300 for this repair.

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