Alarming noises while driving in snow likely have a simple explanation

Dear Car Talk:

I have an '07 Chevy Tahoe. I had an '02 prior to this one, and it was indestructible. The '07 has an issue that no one can figure out. This sounds ridiculous, but I've got witnesses who have driven it and have had the same experience. When I drive my Tahoe in the snow, it bucks and bangs and sounds like a piston is going to come up through the hood – but only in frozen precipitation! This does not happen in the rain or in nice weather, only when it's snowing. What the heck? – Courtney

RAY: They all do that, Courtney.

I think what you’re experiencing is the traction control working. The traction-control system is tied into the truck’s antilock braking system (ABS). When the computer senses that a wheel is slipping (like wheels often do in snow and ice), the computer uses the ABS to apply the brake on that one slipping wheel – many times per second. The idea is to keep the wheel from spinning, at which point it loses its grip on the road and allows the vehicle to skid.

Anyway, ABS can be pretty noisy. It can sound a lot like bucking, chattering and banging, and maybe even like a piston is going to come through the hood (that’s probably the ABS pump you hear). You’ll also feel the chattering in the brake pedal and steering wheel.

Now, if this is a constant noise, and the traction control is continuously operating while you drive, there may be something wrong with it. You could have one or more bad sensors. But normally that will turn on the ABS warning light. So I’m guessing it’s operating normally, and kicking in only when one of your wheels starts to spin.

Here’s how you test it: Pull out your owner’s manual. That’s that thing gathering dust in the back of your glove compartment, behind the gas receipts and the empty packs of Dentyne. Look up “Traction Control” in the index, and find out where the “Traction Control Off” button is on your Tahoe. Then, next time you experience this effect, turn off the traction control.

If the noises stop during acceleration and you slide toward the guard rail, you’ll know it was the traction control working. Note that even when you turn off the traction control, the ABS still will operate if a wheel skids when you’re stopping.

If you believe the noises really are continuous while you’re driving in snow, rather than intermittent, then next time it snows or sleets, stop by the Chevy dealer and ask a service guy to take a ride with you. My first guess is that he’ll tell you that what you’re hearing is the traction-control system doing its job. My second guess is that he’ll try to sell you a 2018 Tahoe anyway. Good luck, Courtney.

Switch or bulbs to blame for low-beam outages

Dear Car Talk:

My wife has a 2007 Solara. This is her second one. I have had the same problem with both of them. Frequently, one – sometimes the left, other times the right and occasionally both – of the low beams will go out. If I just move the headlight switch from Auto to either Off or On and then back to the Auto position, the problem is fixed for a while. I've taken the car to the dealer, and they can find nothing wrong. I've replaced the bulbs, and so did the dealer. But nothing has fixed the problem. Do you have any ideas? – Ken

RAY: There are two possibilities, Ken. If your Solara has HID (high-intensity discharge, sometimes called Xenon) headlights, it could very well be bad bulbs. Priuses, Camrys and Solaras had lots of problems with their HID bulbs failing prematurely.

Unlike halogen bulbs, HID bulbs can fail intermittently – like you describe. So your bulbs may just be failing sooner than they’re supposed to. If your dealer didn’t mention that, it’s either because he doesn’t have an answer except “more bulbs,” or because you have standard halogen bulbs.

If you do have halogen bulbs, then I’d guess that you have a bad multifunction switch, since fiddling with the switch always seems to fix it. That’s the stalk that comes out of the left side of the steering column and operates the turn signals and headlights.

If both of your headlights were always failing simultaneously, I might suspect the daylight sensor, which makes the lights go on and off when you set the switch to Automatic. But since that sensor merely turns the switch on and off, it would affect both headlights, not just the right or left.

If you have halogen bulbs, I doubt it’s the bulbs themselves. Standard bulbs pretty much either work, or they don’t. So if you can get a bulb that’s dead to come back to life and then stay on by monkeying with the switch, the bulb is unlikely to be the problem.

The multifunction switch could fail intermittently, like you describe. If it happens to be working fine the day you take it to the dealership, they would find nothing wrong.

Under the mechanics’ code of conduct, they still shouldn’t have let you leave without selling you a new multifunction switch and a new transmission, but that’s water under the bridge now.

Of course, the best thing to do would be to get your car to the shop when the lights are misbehaving. Then a mechanic can check and see if there’s current reaching the bulb sockets. If there’s no current getting to the bulbs, then you’d strongly suspect the switch.

But as we know, headlights usually fail when? At night! When the dealership is closed. So you may have to take your best guess. You can’t just drive around at night with your lights going out.

So ask the parts department how often they have to replace multifunction switches on Toyotas in their shop. If their answer is anything other than “never,” ask them to try one for you, Ken.

And if it doesn’t fix the problem, maybe they’ll be nice enough to take the part back and charge you just for the labor. Then you can buy one of those 250-watt halogen work lights at Home Depot, plug it into the cigarette lighter and prop it up on your dashboard. Good luck, Ken.

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