Dear Car Talk:

My 16-year-old son has been driving my mother's 1997 Honda Accord for a couple of months now, with the intent to buy it from her once he's saved enough money. The car was bought new, and has always been very reliable. Recently, though, he has had some starting issues. Sometimes when he turns the key in the switch, the car not only will fail to start, but the horn will sound. The horn stops as soon as he turns the switch back off. Sometimes when he tries again, it starts, but other times it keeps doing the same thing, and he has to find other transportation.

At first I thought he must be doing something wrong. But last week, we were in the car together (he was driving), and it did the same thing. I didn't see him do anything incorrectly, and the car started on the second try. I can't imagine what might be causing this, and it's had several mechanics scratching their heads. It happens only when the car is warm; it has never failed to start first thing in the morning or when it has been sitting for a few hours. This car has been a great one, and my son is excited to own it, but this issue needs to be addressed before I feel good about turning it over to him. I hope you can help us. -- Bill

I'm not sure why he's so eager to own it, Bill. It's a lot cheaper to borrow it. If it were my kid, he'd borrow it and just try to wait Grandma out.

I'm guessing that the problem is related to the built-in alarm system. Many cars come with an immobilizer that prevents the car from being started under certain conditions. Like, if the door is not unlocked with the key, the system will conclude that someone broke in, and will immobilize the vehicle. Or if it's 2 a.m. and a guy named Bruno is sitting behind the wheel with a crowbar and a bunch of ignition wires in his teeth.

Or perhaps the key itself is faulty. Lots of cars of this vintage have keys embedded with computer chips that have to be recognized by a reader in the ignition switch before the car is allowed to start.

So the first thing I'd do is ask Grandma if she has a spare key, and try that one. If she lost the spare 16 years ago, your Honda dealer can make you a new one using the vehicle identification number and proof of ownership.

If a new key doesn't help, then you might just want to take the car to a good mechanic and have him disconnect the immobilizer entirely. The car has already been effectively stolen by your son, Bill, so Grandma really has nothing to worry about.