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What to Do 'When ABS Light, Traction Control, Stabilitrak Lights Go On

Chriscamaro learns and writes about about car modding and electronics.


What Is It Like When Your ABS or Traction Systems Fail?

You'll be at an intersection trying to make a left-hand turn and in the middle of the turn, your ABS will activate, causing your brakes to shudder, stopping you halfway through your turn, with oncoming traffic approaching. Or you might be driving along on the highway and going over an overpass when the joints in the concrete shake the car a little and cause the dashboard to light up and beep at you for a second or two before going out. Heck, you might even have this problem when it rains but not when the weather is nice and dry.

These unexpected occurrences are an early warning sign that your traction system is failing.

The first consequence when these electronic features fail is that you won't have any electronic driver-assisting traction control features anymore. That means:

  • no ABS to help the car stop quickly on icy or wet roads.
  • no Stabilitrak to help you negotiate turns at high speeds without losing grip on the road; and/or
  • no Traction Control to help you climb a slippery slope without spinning your tires hopelessly.

But to be honest, the lack of these features isn't a big problem in itself. In fact, when your car loses these features, that just makes it equivalent to any car from the 20th century, when cars didn't have these features at all.

The real problem for you is going to be the danger of driving your car with a half-failing system. As the system transitions between fully working and fully broken, there's a period in between where you'll experience unpredictable driving behaviour, where any or all of the brakes may activate without warning, at inappropriate times, possibly causing you to get stuck in a dangerous situation, or worse yet, causing you to lose control of the car. This is the opposite of what the car is supposed to do, so let's fix this half-failing system so you don't have to worry about it anymore.

How Your Car's Computer-Assisted Traction Systems Work

Your modern car provides you with an extra layer of safety and peace of mind by intelligently activating the brakes on the car individually or collectively, so that you always stay glued to the road. This can be done in a way that no human could ever reproduce, because of the speed and sophistication of computer control.

When you step on the brake pedal, in an old-fashioned car, you're physically pushing hydraulic fluid onto the four sets of brake pads attached to the four wheels on your car. This squeezes the brake pads together and grips the wheels, causing the car to stop. It's not that much different from how bicycle brakes work, if you've ever looked at those.

Now imagine that instead of just squeezing all four at the same time, using your foot, the car's computer brain is individually squeezing specific brakes hundreds of times per second, depending on which ones happen to be losing traction and which ones are still sticking well to the road. This is essentially how traction control works. The car's computer senses and monitors the angle of the steering wheel and the individual rotational speeds of each wheel to see if they are all spinning in synchrony with one another and if those relative speeds make sense, given the speed of the car and the angle of the turn. If anything is out of whack, the car tries to restore the balance by applying brakes selectively to individual wheels, using hydraulic pumps for each wheel.


What Happens When Traction Control Systems Malfunction

So this elaborate safety and traction control system includes the car computer, various sensors, and various valves. If anything malfunctions, the entire system is affected.

Since each wheel on the car has its own "wheel speed sensor" and a pump with multiple valves, you have several elements that could be faulty, plus the steering wheel angle sensor, if applicable, various accelerometers, and on top of that, the wiring connecting all this stuff back to the computer.

The computer gets confused when the signals it receives don't make any sense. For the safety of the driver, It is supposed to respond to conflicting signals by deactivating the entire control system, returning the car to the old-fashioned non-electronic way of braking and accelerating. But the problem is, the car computer has a hard time telling if a signal is caused by a fault in the system or by a legitimate low traction condition. This is why the system can activate inappropriately and cause problems for the driver.

So What's Wrong With My Car?

Ok so let's break this down a bit. If your car suddenly misbehaves when you are braking or steering, with an ABS, Stabilitrak, or Traction Control light going on, here are the likely root causes:

Red Herrings: When the Root Problem is Not the Traction Control System

  • If your tires have uneven pressures in them, this can cause the system to malfunction.
  • If you just had an alignment done, this can throw off the steering angle sensor or otherwise confuse the system.
  • If you changed tires or wheels and they don't have the same diameter they did before, this can also be a culprit.

When the Problem Actually Is the Traction Control System

Now for the real stuff...

1. Bad Wheel Speed Sensor

The wheel speed sensors measure how fast each wheel is spinning. These are located INSIDE the wheel hub (some people call this the wheel bearing). Therefore replacing the entire hub or bearing is necessary to fix a faulty speed sensor. You can do this yourself if you are mechanically inclined but it's no big deal for a mechanic to do it also.

2. Bad Steering Angle Sensor

This is usually located inside the steering column and measures the rotational angle of the steering wheel. If this fails, it can be replaced, but this usually involves removing the steering wheel and that can be dangerous because you could deploy the airbag and kill yourself. So I don't recommend messing with it. But a certified mechanic can fix this fairly quickly.

3. Bad ABS pump

Hydraulic fluid to each set of brakes is controlled by a pump and valve assembly that modulates the flow of fluid to individual brakes. If this fails, the entire system will de-activate. These units can be purchased and replaced by a mechanic fairly easily.

4. Bad Wiring

Old cars have old wiring. Old wiring gets brittle and breaks down, causing intermittent signals that will confuse your car's computer. Road debris, water, abrasion and all sorts of normal wear and tear will cause wiring to fail over time. Perhaps one of the most common points of failure is the wiring that connects the wheel speed sensors back to the car computer because these wire looms flex when the wheels rotate and the suspension travels up and down. They are also exposed to dirt, grime, water and heat so it's no wonder they either short out or disconnect. It's important to inspect your wires and connectors before jumping the gun and replacing something more costly.

5. Blown Fuses

The ABS pump motors in particular run through fairly high amperage fuses in your fuse block. If one of them blew, that motor won't work and will report the same way as if it were broken. It's quick and easy to change a fuse, so if you're getting a code related to the pump, check the fuse first.


A Word About Wiring

This is perhaps the most common root cause of traction control failure, especially in older GM cars. Quite simply, the wires are the weak link in the system, as they just aren't protected all that well from wear and abrasion. Often times you can see the damage visibly if you just have a look with your own eyes, in your own driveway. Turning the wheel hard over to one side and then the other, you'll be able to actually see the wiring coming out of the wheel hub and going back along the suspension and chassis to the computer. If there is any damage, some electrical tape and a soldering iron can buy you weeks or even months until you can get a mechanic to replace the wire loom (see the video below).

Find and Fix the Problem

How to Drive Safely When Your ABS/Traction Control/Stabilitrak is Malfunctioning

As mentioned earlier, the danger of having an intermittent or half-working traction control system is that you never know when it will activate and interrupt your driving maneuvers. Fixing this unpredictable situation is very simple and involves deliberately failing the system by disabling one of its components. This can be done by removing one of the ABS pump fuses. Removing the fuse will deactivate that pump and tell the computer the system is malfunctioning. You'll get several lights on your dashboard indicating that the system is out of service, but at least you can drive the car normally without having to worry about the system glitching out in an unsafe way. See the video just below for this procedure.

Deactivating the ABS system as described here will NOT stop your brakes from working. They will work normally.

Driving Safely Until the Problem Is Fixed

Diagnostic and Repair Procedure for Traction Control System

The first thing you should do is scan the car for codes using an OBDII scanner. There are several you can buy in any store that has an automotive department. Your mechanic may charge a small fee if you ask him to do it but either way it's a fairly cheap investment to narrow your search down significantly. If there are any codes, they may tell you the steering angle sensor is the problem or tell you which exact wheel speed sensor is misreporting.

If you get a code for a wheel speed sensor, check the corresponding wire loom first (see first video) and then change that wheel hub. If the code is for an ABS pump, check the corresponding fuse and then replace the unit. If the code is for the steering angle sensor, that sensor may simply need to be re-calibrated or possibly replaced by a mechanic.

If there are no codes, it likely means the system is OK when parked in your driveway and is only faulting out for a split second when you go over a bump or turn the steering wheel or something. If this is the case, you'll want to check the wiring for visible signs of damage (see first video).

If there are no codes and you are unable to find damage in the wiring, the only recourse is to have a mechanic manually inspect all elements comprising the system and repair or replace them as necessary.

This article is accurate and true to the best of the author’s knowledge. Content is for informational or entertainment purposes only and does not substitute for personal counsel or professional advice in business, financial, legal, or technical matters.