Dear Tom and Ray:

I have a 2006 Toyota Sienna CE model with approximately 85,600 miles on it. Recently, I changed two of my tires and had a wheel alignment. Since that time, my tire-pressure warning light has been coming on. I took it to the mechanic, who replaced the tires, and he checked and found nothing wrong. He said the tire pressures are all fine, and he said to just drive it and the problem will go away by itself. I've driven it for a couple of days now, and the light is still coming on. When you start the car, the light doesn't come on right away. But then after driving five to seven miles, it comes on. The tire pressure is good. I am checking it every day. Any idea how I can resolve this matter?

-- Mir

RAY: Yeah -- by going back to the mechanic with a tin of warm brownies. That often gets us to try a little harder. That's what your guy needs to do.

TOM: My guess would be that when he changed your tires, he accidentally damaged one of the tire-pressure sensors.

RAY: On the part of the valve stem that sits inside the tire is a pressure sensor with a little transmitter. That sends information about the tire's pressure to the car's computer.

TOM: The tire-pressure warning system on the '06 Sienna does not tell you which tire is low, so you don't know which of the two sensors got damaged.

RAY: But here's what you can suggest to the mechanic. Tell him that while you're not absolutely sure, it seems pretty likely that one of the tire-pressure sensors got damaged when he changed the tires.

TOM: Then make him a deal. Have him put new sensors in those two new tires. He can do them one at a time if he wants to. Maybe he'll guess right the first time -- he's got a 50-50 shot -- and he won't have to do both.

RAY: And if a new pressure sensor -- or pressure sensors -- makes the light go off, then it was pretty obvious that he's responsible, and you're all set.

TOM: But if he changes both sensors and that doesn't fix the problem, then you've determined that he's not at fault -- in which case, you'll pay him for that extra work.

RAY: In that case, it may have just been a weird coincidence, and a sensor in another wheel just happened to fail after your tires were changed. But I doubt it. Good luck, Mir.