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nelsonba 12-02-2015 11:59 AM

ABS/Traction Control Sensor Question
Hello. I have a 2005 Saturn Vue. The ABS and TC lights came on and the problem was diagnosed as a bad sensor. Additionally, the wheel bearing was bad on the same wheel. This part was replaced 1 year ago after an accident. We were scheduled to bring it in for a warranty repair, but the day we were scheduled to take it in my wife was driving in icy conditions, hit the brakes and slid into a curb, which damaged the lower control arm. What Iím wondering is if the ABS malfunctioning could have contributed to her inability to stop the car before hitting the curb. She wasnít going very fast at all (coming to a stop at an intersection), and Iím a little surprised the control arm was bent to the point where it was not drivable. At this point the shop has agreed to replace the wheel bearing and sensor, but Iím on the hook for the control arm. What Iím wondering is whether or not I have a case for getting the control arm repaired at their expense as well? I just donít know enough about how the system works to know whether or not a functioning sensor could have prevented the impact. Thanks for any help!

goBoating 12-02-2015 05:32 PM

Re: ABS/Traction Control Sensor Question
If you/your wife chose to drive the car knowing the ABS/TC was inoperable, you accepted the risk.

Re: your wheel bearing - sensor problem. Our ABS/TC failed on our 2004 Vue. Procrastinated about getting it fixed until a front wheel bearing went bad. When I took it in, the shop said hold off on the ABS/TC repairs as they had seen bad wheel bearings cause the problem. When the bearing gets sloppy, the motion of wheel get irregular and the wheel speed sensor can't track it. They redid the bearings and the ABS/TC magically fixed itself. 'Still working.

If you have ABS/TC problems again, it may the other front bearing failing.

Chazberry 12-02-2015 09:28 PM

Re: ABS/Traction Control Sensor Question
[QUOTE=nelsonba;2169604]I just donít know enough about how the system works to know whether or not a functioning sensor could have prevented the impact.[/QUOTE]

As the name implies ([B]A[/B]nti-Lock [B]B[/B]raking [B]S[/B]ystem), it is designed to prevent the wheels from locking when they lose traction (the brake fluid pressure is pulsed on and off so that the brakes release momentarily so the wheels turn enough to get a new grip), thereby allowing you to stay in control in [U]some[/U] circumstances. I doubt anyone could say whether or not it works well enough to have prevented your wife's impact with the curb, not knowing speed and exact conditions.

As far as bad bearings causing a sensor to fail, I find it very unlikely as the Reluctor is buried inside the wheel hub . . .


If the bearing was bad enough to do damage to the Sensor, I think you would have better indications than an ABS light. I've had at least 4 hubs fail to the point of experiencing some load roaring noises, but no ABS lights.

fdryer 12-02-2015 09:31 PM

Re: ABS/Traction Control Sensor Question
Unfortunately, there are no guarantees with brake systems, with or without abs/tc. What isn't discussed openly is the separation of effective brakes on different surfaces and if abs helps. A flat dry surface gives the most traction for braking as long as speed is within the range for maximum braking without locking up brakes that increases braking distances. Any other surface that isn't flat or dry now increases braking distances due to less traction, or the ability of the tire foot print to remain glued to the surface. Once speed exceeds traction in poor weather conditions, braking effectiveness quickly decreases - one or more wheels lock up and a skid occurs where braking distances increases. There's always the delicate balance of calculating speed for the conditions that allows best traction control without sliding or skidding while allowing the most effective braking. ABS with traction control allows another dimension of braking.

Other than dry flat surfaces to allow braking in the least distance, abs allows shorter braking distances due to the higher traction available on flat dry surfaces. All other surfaces (wet leaves, rain, ice, snow, gravel, sand) reduces braking effectiveness and increases braking distances, more so when abs is involved. Anyone thinking/assuming abs will prevent a crash only fools themselves. All abs does is [U]increase[/U] braking distances on slick surfaces while attempting to slow a vehicle down. This presumes speed was already higher than conditions allows for maximum traction or the ability of tires to stay glued to the ground. Once speed is higher than tire traction allows, braking is already compromised; in vehicles without abs, the wheels lock up and the vehicle slides. In vehicles with abs, the slide is prevented by high speed abs cycling brakes on and off to prevent wheel lock up. In effect, when abs detects wheel lock up, it automatically releases enough brake pressure to allow that wheel to continue to turn at the same speed as the others. Once this wheel speed increases back up to the other wheels, abs applies braking. This becomes the high speed foot massage felt by drivers in an abs applied braking situation. Releasing brake pressure on one or more wheels means braking distances increases a small amount that accumulates overall as longer stopping distances. There's little choice here as the speed is already too high for regular braking when a skid is guaranteed, even in slow speed icy conditions where tire traction is lowest. Once abs is involved, all one can do is steer and hope to avoid crashing.

Icy conditions should be viewed as similar to ice skating or sledding. Maximizing gliding distance with little effort and having little to no braking (other than learning the hockey stop or digging in the toe piece). Anyone walking on ice knows how slippery it is. Shoes that don't slip on dry ground now slides on ice. The same applies to vehicles weighing over a ton with four 'shoes', the tires that grip on dry surfaces having almost not traction on ice. Black ice, where the black asphalt hides ice and doesn't reflect light is hazardous to anyone not aware of freezing weather conditions. Driving is always hazardous no matter what experience a person has. Recognizing the many conditions we all experience in driving in every weather condition eventually reveals the hazards of assumptions when abs is counted on to avoid accidents. Its wiser to never assume abs will help and drive as if abs didn't exist. Far too many assume abs will allow higher speeds for braking and learn the hard way that it doesn't guarantee anything.

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