4

I have had issues with ABS light for around a year where the light occasionally comes on and off. However, the brake pedal has been misbehaving only in the last two weeks and I am getting really concerned about this.

The braking issue according to my observations which may or may not be 100% accurate happens, only when:

  1. The orange ABS light has not yet lightened up in dashboard;
  2. I am driving at low speeds (5-10 mph);
  3. I turn steering wheel and apply brakes at the same time.

Then the brake pedal sometimes is pulsing and the braking distance seems to increase quite dramatically. Then the ABS light turns on and brakes work normally for the rest of the time. It is not easy to reproduce this issue. On average it happens once every two days.

Is the pulsing brake pedal necessarily an ABS issue? I have been reading that ABS should not engage at low speeds, so it makes me think it may be something else.

How can I temporarily disable ABS to prove or disprove that this is ABS issue?

Car is Chevrolet Aveo 2007 sedan. The roads are dry hence ABS should not engage.

Update#1: now also the red "brake" light occasionally turns on while driving even though parking brake is disengaged. Though the car seems to operate as before.

3

It could also be a defective strut or shock absorber. I am having the exact same issue myself presently. When a strut is empty of fluid and gas there is no dampening effect and you are bouncing on your springs. This effect is also noticed when braking at low speeds as well as when turning. When braking with dead struts your tires have intermittent contact with road and your ABS tries to compensate. I will having the front struts changed in a few hours time and will get back to you and tell you if the problem is remedied.

Update: Good news, Struts are changed and it appears that that issue I had finally solved. Now my problem is relearning how to drive without having to constantly compensate and bouncing all over hell's half acre. :)

  • Glad you figured out your problem. I noticed that the ABS most likely is to kick in when I drive into my driveway (uneven surface with steering wheel turned). Do you think it may be possible to see with naked eyes if one wheel does not have enough contact with ground? Any other tips how to prove or disprove your hypothesis on my car? Thanks! – john1234 Jul 20 '16 at 6:25
  • @John1234: That was the only time that my ABS would kick in unexpectedly was on uneven road surfaces and while turning. On good condition dry roads didn't activate so easily. As for whether or not you could see it naked eyes I don't know but you might notice it by feel in the steering wheel. All I know is that when I changed the struts the problem disappeared. – Old_Fossil Jul 20 '16 at 16:40
2

Brake pedal pulsing is most likely ABS engaging. To disable ABS, remove the fuse for it in the fuse box that is under the hood. Do have a shop look at your ABS system if the light has been coming on. Erratic brakes are not something you would want. enter image description here

1

I believe this is due to a warped rotor. The pulsing will be due to raised areas on the rotor pushing back against the brake pads.

  • 2
    Warped rotors would make the pedal pulse all the time, not just some of the time. – tlhIngan Jul 18 '16 at 3:30
  • 2
    Pulsing pedal because of rotor issues should be easily distinguished from ABS kickback. Shouldn't really affect braking distance nearly as much either. – I have no idea what I'm doing Jul 18 '16 at 9:48
  • @tlhIngan - Not so. I'm experiencing it right now in my truck where it doesn't pulsate all the time, only under certain load. – Pᴀᴜʟsᴛᴇʀ2 Jul 18 '16 at 11:28
  • @MeltingDog I think in my case "pulsing brake pedal" is indeed due to ABS kickback, because 1) in my case the pulsation is more obvious than here (youtube.com/watch?v=4rfciRq2JzU) and 2) removing ABS fuse has made "pulsing brake pedal" issue go away. Do you think that warped rotor could also make ABS kick in when it is not supposed to (in the answers three root causes have floated - bad sensor, bad struts and possibly bad rotor)? – john1234 Jul 20 '16 at 6:40
  • @john1234 honestly, I'm probably not the best person to ask as I've never worked on a car with ABS but I do know that the ABS sensor reads off a toothed sensor ring that is separate to the rotor. Unless the damaged rotor has impacted this then I would tentatively say no. buyautoparts.com/images/abs-speed-sensor-image.jpg – MeltingDog Jul 20 '16 at 22:12
1

This has happened to me with a defective ABS sensor (front, passenger). I mistakenly gouged it while changing the wheel bearing which caused it to intermittently give false signals at lower speeds (ABS ring turning slowly = sensor misinterpreting it as stopped?). Typically faulty sensors will throw the ABS warning light, which mine eventually did.

protected by Community Feb 21 '18 at 11:42

Thank you for your interest in this question. Because it has attracted low-quality or spam answers that had to be removed, posting an answer now requires 10 reputation on this site (the association bonus does not count).

Would you like to answer one of these unanswered questions instead?

Not the answer you're looking for? Browse other questions tagged or ask your own question.