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Almost every modern car will have a traction control system of one kind or another. These systems are designed to help keep the car on the road in difficult, slippy, or out-of-control situations.
Sometimes when you’re driving, the traction control light will come on. What light this appears as varies from manufacturer to manufacturer. Sometimes it will be a picture of a car losing control, with skid marks from the tires behind it. On other cars, it can be a lit-up “TC” that flashes. It’s worth checking your owner’s manual to make sure you know exactly which dashboard light represents the traction control system.
When the light comes on, it means that the traction control system is active. Usually, there will be a good reason for this. Occasionally, sensors in the car may have become old and corrupted, and this may trick the car into thinking the traction control needs to be active when it, in fact, doesn’t.
Either way, in this article, we will go through a few of the possible reasons for your traction control light being on.
What is Traction Control?
It works, in essence, by ensuring that the tires can always grip the road as efficiently as possible. The more grip the tires have on the road, the higher your chances of being able to control the car.
Older cars – particularly those massive rear-wheel-drive brutes of the 1960s – often utilize a limited-slip differential to aid with traction. This differential goes across the rear axle of the car. If one of the wheels has more traction than the other, the limited-slip diff (as it’s commonly referred to) transfers power to that wheel. This results in the driven wheel with the most grip getting the most power, helping to reduce wheelspin and increase traction. These limited-slip differentials are still used on many cars today, but only to back up the electronic traction control system.
In newer cars, an electronic traction control system is far more common, because it’s lighter and uses sensors and parts of the car that have already been installed. Electronic traction control systems use the same system as the ABS (anti-lock braking system).
Using the ABS wheel sensors and braking controls, traction control systems usually pulse the brake of the wheel with less traction. In most cases, this will be enough to set you straight on the road. Some more advanced traction control systems will automatically reduce engine speed or send power directly to individual wheels.
What is ABS?
ABS should come on when you have to brake hard, especially if you are also turning the wheel. When you have to brake hard (and turn), there is a high likelihood of the wheels locking up. If this happens (as you may have seen from motorsports), you’ll lose all traction – this being all your turning power and all your stopping power. It’s a very dangerous situation.
To combat this, ABS causes the brakes to pulse on and off very quickly. This allows the wheel to turn a slight amount before the brakes come back on again. As the wheels turn, you have the best chance possible of regaining traction. As soon as the car has traction again, the ABS will stop pulsing the brakes and sit back, waiting for the next time it’s needed.
Some Reasons Why Your Light Might Come On
If the light comes on briefly before going away again, this is nothing to worry about. The traction control system is designed to do this. It just means the car is letting you know that the traction control system had to kick in for a moment there because one of the driven wheels (driven wheels means the wheels that the power is going to) was slipping, but no worries, we’re all safe, let’s carry on.
This kind of situation might happen if you accelerate very harshly or are driving along a slippy surface, such as ice, snow, or mud. In these situations, all we’d say is that no traction control will protect you indefinitely – you need a car that’s up to the task in hand. Make sure it’s front-wheel-drive or four-wheel-drive (not rear-wheel-drive), with good ground clearance, and winter or off-road tires. This will make all the difference, trust us.
In terms of your traction control light, there might be more of a problem if the light stays on. If that happens, we would recommend pulling over to the side of the road and calling out a mechanic. Although we wouldn’t recommend it if you do decide to keep driving, make sure you drive slowly, carefully, and away from heavy traffic and pedestrians.
When the light is on and stays on, you know that you have a problem with your traction control system, somewhere. The main parts of the traction control system are the ECU and the wheel speed sensors (also part of the ABS).
Let’s look in more detail now at some possible reasons why your traction control light might be stuck on.
First off, let’s reconsider the “bad weather” situation. If there’s a constant stream of snow batting against the windshield and covering the road again every 10 seconds, your traction control system may need to be on for significant periods. It’s also possible that the traction control can’t cope with the serious conditions you’re driving in.
In this extreme situation, it’s probably worth stopping and waiting for the weather to pass. A situation may arise where you have to brake or turn sharply (especially likely in inclement weather). If the traction control isn’t working, you’ll find it very difficult, which could easily lead to a crash.
Faulty Wheel Speed Sensor
The wheel speed sensor – no surprises here – measures the speed of the wheel it’s attached to. This is primarily part of the ABS; if the ECU realizes that the wheel on one side of the car is turning more than the wheel on the other side of the car, it knows there is a loss of traction, and thus the ABS and traction control systems are activated.
If one of these sensors is damaged, it could trick the ECU into thinking there is a loss of traction, which would cause the light to come on.
ECU Processing Issue
The ECU – Electronic Control Unit – is the brain of the car. If something goes wrong here, it won’t be processing information correctly.
This could lead to any number of issues, one of which could be the traction control light. It’s possible and likely that you’ll notice many other strange goings-on too.
If there’s a problem here, you’ll need an expensive ECU reprogramming session from a professional.
Steering Wheel Angle Sensor
This sensor is used in cars with electronic power steering (as opposed to the traditional hydraulic power steering). If this sensor develops a fault, it has been known to trigger the traction control light to come on.
You may also notice that your car isn’t driving straight – the tracking might feel out. When you hold the wheel straight, the car may pull to the left or the right. If this is the case, get your steering wheel sensor, and the tracking looked at.
Sadly, unless you have some very advanced diagnostic equipment lying around in your garage, most of these problems require specialist workers. The repairs are unlikely to be particularly cheap, but once you know what the problem is, it’s, of course, possible to give them a go yourself.
If your traction control light is on, your car may have limited traction. Always be safe while driving.