CarTalk.com Blogs Car Info Our Show Deals Mechanics Files Vehicle Donation

Airbag sensor repair verification?

I just had my 2003 Subaru Forrester serviced because my airbag warning-light went on. (No impact, no apparent cause).

My mechanic said it might just need to be reset, but at worst, he might need to replace a $300-400 sensor in a bumper. He did a computer-diagnostic & called me back with “good news” that the 2 side-airbag sensors located under the front seats needed replacing for only $200. I said OK to the repair. (Perhaps I should have asked him to show me the sensors he’d removed, but I didn’t.)

There are just 3 things I’d like to know, to understand airbag sensors better, and to reinforce my trust in my mechanic:

>Is it true that you must replace both under-seat sensors, not just one at a time?

>Can the airbag light ever go on and just need to be reset, without the need to replace anything (like a wire, or a switch in the dashboard ), or can I be pretty sure that my mechanic had to replace something to make the light go off (so he probably replaced what he said he did)?

>Do sensors often just “go bad” without external cause? (No one recently moved/kicked anything on the floor or jammed anything under a seat).

I’d be very grateful for a little background info!!

I don’t know if this would apply to your vehicle, but once in a while my air bag light used to come on and I found it was due to a loose connection under the drivers seat.

Reason being, the wife and and drive the same vehicle and have to reset the seat location each time.

Moving back and forth loosened the drivers seat side air bag connector under the seat and after disconnecting and spraying electrical contact cleaner in it, reconnecting and applying a little dielectric grease on the connection, I’ve had no more problem. That was over a year ago.

Too bad you didn’t have a chance to check connections before you gave him the go-ahead.

Can the sensor go bad without any external indication? Sure, these things are mass produced like most everything else today. Being man made, things are pretty much guaranteed to go wrong sometime.

Computers that control the manufacture are only as good as the info injected into them.

Passenger seat occupancy sensors do go bad. The way you know why the light is on is the system has a diagnostic feature.

My experience is with BMW and there is just one occupancy sensor for the front passenger seat.

It doesn’t make sense the drivers seat needs a occupancy detector.

Sure the light can come on and you can re-set the light, but it probably will come back on,if a light re-set fixed a problem, then their is either a intermittent hardware failure or a problem with the software.

What is probably going on is your mechanic is dealing with sensors other than occupancy detectors