Malfunctioning tire-pressure sensor will activate dashboard light.

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Dear Car Talk: I drive a 2006 Toyota RAV4. A few months ago, I got new tires. The low-tire-pressure indicator light has been on almost constantly since the new tires were put on. I have been back to the tire shop countless times for them to turn off the indicator light. The guys tell me there’s nothing wrong with the tires. They also check the tire pressures and say they’re fine. The light stays off until I get on a freeway, then on it goes again, and back to the shop I go. I do know that one of the tire sensors had to be replaced on one of the rear tires when the new tires were put on. What can I do to fix this? — Patsy

A: One of your tire-pressure sensors is bad, Patsy. Each tire’s pressure sensor is housed in the valve stem. A few minutes after you start up the car, each one communicates, wirelessly, with the car’s computer.

If the pressure is low, the computer makes the dashboard light go on. Or, if one of the sensors does not communicate at all, that also makes the light go on. Since your tires’ pressure is always fine, I’m guessing one of the sensors is not working at all.

It could be that they replaced your pressure sensor with a non-factory sensor. And perhaps that after-market sensor just doesn’t communicate with your car’s computer.

Or, if they damaged one of the sensors when they changed the tires, they easily could have damaged another one (or more than one) and not known about it at the time. But since you’ve been back 150 times, you’d think these guys at Einstein Tires would have figured it out by now.

So if you’re still on speaking terms with them, go back and ask them to scan your computer and find out exactly which sensor is not working.

If it’s the same one they replaced, ask them to replace it again, this time with a Toyota sensor. You can pay the difference in the cost of the part, and they can eat the labor.

Or, if it’s a different sensor, you can have them replace that broken sensor, and see if you can guilt them into giving you a break, because they probably damaged it when changing the tire. Plus, they owe you something for pain and suffering. And for diagnosing it for them.

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