Dear Car Talk:
I hope you know what is wrong with my 2002 Cadillac Eldorado. I can be going 70 mph (or 50 or 40) around corners, and it will slam on the brakes and reduce my speed 40 to 20 mph. I have had the steering-angle sensor replaced, and it still had the problem. I took it to a GM dealer, and he replaced the yaw sensor and thought it was fixed. But it did it to me again, so I'm taking it back in. He is baffled.
This is dangerous, as we were on a mountain pass with no pull-overs and with semi trucks behind us and next to us, we were going 70 miles an hour, and the car slammed on the brakes and reduced our speed down to 40 mph before the brakes released. I thought we were going to be killed. Help me!
I hope you have a good dry cleaner, Arlene. That is frightening, and terribly dangerous. The 2002 Eldorado has a stability-control system, and I'm guessing that's what your dealer is focusing on. The stability-control system monitors various sensors -- several of which have already been replaced. It monitors the steering angle, the yaw (side-to-side movement) of the car, the comparative rotational speed of the wheels, the pedal inputs, throttle position, vehicle speed and digestive systems of each rear-seat passenger. And if it senses that the car is no longer going where the driver is pointing it (if it skids or starts to flip over), the stability control uses individual brakes, via the anti-lock braking system, to try to bring the car back under control.
Your dealer's theory is that one of the sensors is sending a crazy reading to the computer when the car is turning at high speed. That makes the computer think the car is careening out of control, when it's really not. It therefore takes evasive measures until it senses that the car is under control again. So your dealer has replaced a couple of sensors and crossed his fingers ... while you pile up the dry-cleaning bills.
If this were my family member, I'd just leave the car with the dealer and tell him to drive it until he figures it out. I wouldn't risk this happening again. But if you're feeling daring, Arlene, you should encourage your dealer to approach it scientifically.
You can have him start by temporarily disabling the electronic safety systems. He can do that by disconnecting any of the four anti-lock braking system (ABS) sensors. There's a sensor at each wheel, and if any one of them is disconnected, the ABS and stability-control systems will shut down.
That means you'll be driving without the benefit of ABS or stability control. But if the phantom braking happens even with the electronic systems disconnected, then you can rule out the electronic systems. Then it's a mechanical problem, like the brake master cylinder or the power-brake booster, and you can replace those parts.
If the problem goes away with stability control disconnected, then you know that the ABS or stability-control system is at fault. In that case, the next thing I'd ask the dealer to replace is the computer. If it's not an individual sensor, then it's probably the brains. The computer is expensive, but you might be able to persuade him to "work with you" by mentioning that you've already given his contact number to your next of kin.
The truth is, your dealer can put a new computer in your car and let you drive around with it for 30 or 60 days. And if the problem goes away, you can pay him for the computer and drive without your heart in your throat. If the problem doesn't go away at that point, and you're still alive, Arlene, he can put the computer back on the shelf, not charge you for it, and you can get rid of the car.
You're very lucky that you didn't end up under a truck or off the edge of the cliff last time, and if he can't fix this quickly, I'd stop rolling the dice with this Eldorado.