CARS.COM — All cars and light trucks since the 2012 model year have come with standard traction control, and many vehicles from earlier years that had antilock brakes also got traction control systems. That’s because traction control piggybacks on the antilock brake system (ABS) and uses the same wheel-speed sensors to detect tire slip during acceleration. Traction control and ABS are the basis of the stability control systems the federal government has required since the 2012 model year. Where traction control maintains traction while accelerating and ABS does the same for braking, electronic stability systems compare the vehicle's trajectory to where the driver seems to want it to go and brakes individual wheels to keep it on course.
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As with antilock systems, the wheel-speed sensors, wires, connectors, control module and other components can occasionally conk out or suffer intermittent problems. The sensors, wires and connectors are located at each wheel and live in a hostile environment of potholes, water, snow, dirt, tar, stones, other debris and more, so they take a beating and can fail.
A problem in the system will usually illuminate a dashboard warning light that traction control is disabled and, in some cases, ABS is disabled as well. (When ABS is disabled, you should still have normal braking, just without the antilock action.) This is different from momentary illumination of the warning light; the light should always come on for a couple of seconds whenever you start the vehicle as well as when the system detects that a wheel is spinning freely and does its job to improve traction.
Wheel-speed sensors are supposed to detect when one drive wheel is spinning faster than the others — meaning the vehicle is slipping or losing traction. The system will then reduce power and/or apply the brakes to that wheel. Braking the spinning wheel allows the power to go to the other drive wheel or wheels that have more traction. (This principle is what has allowed ABS-based traction control in some vehicles to take the place of limited-slip differentials, which serve the same purpose.) When traction control is disabled, you’ll have to control tire slippage the old-fashioned way: by lifting off the accelerator.
In some cases, the warning light can come on because wheel-speed sensors are covered with road grime or debris. Several GM models from recent years have had this problem, and GM issued a technical service bulletin to dealers to address it.
When the traction control warning light stays on, that means you aren’t getting any help from the system to control traction and the system needs to be checked. Unless you're driving on slippery surfaces, traction control doesn't come into play, so getting it repaired isn't as crucial as it would be for disabled ABS or stability, which are arguably more important as safety features. A driver can prevent most wheel slippage during acceleration by going easier on the gas pedal. Diagnosing issues usually requires a scan tool to read the trouble code that triggered the warning light. Scan tools can help pinpoint what the issues are (such as a bad speed sensor or connector) and at which wheel(s).
Though traction control provides benefits, it can sometimes be an impediment to progress, such as when entering or leaving a parking space with rutted snow. Some systems are so sensitive that at the first sign of wheel slip, they immediately reduce power or apply the brakes so much that you go nowhere. Fortunately, a traction control system can be turned off in most vehicles, and you can then resort to the time-honored technique of rocking your vehicle back and forth to power your way out of the snow.
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