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What is Electronic Stability Control (ESC)?

ESC, or Electronic Stability Control goes by many names… but what is it and why is it such an important automotive safety feature?

Both Bosch and Continental and also BMW and Mercedes-Benz are credited with the development of traction and stability control systems. From there, other car makers began developing their own versions, usually with a Bosch system as the core unit, although General Motors developed its own system in conjunction with Delphi Automotive.

In Europe, 2007 saw it mandatory for all new vehicles sold to have ESC as standard. In 2009, the Australian Government introduced an Australian Design Rule that made it mandatory all new passenger cars and SUVs be fitted with ESC, although that didn’t take effect until 2011 and in 2013, it was mandatory that all new vehicles sold in Australia have ESC as standard.

The European and Australian decisions to make the fitment of ESC to new cars mandatory came about after a test by Swedish automotive outlet, Teknikens Varld which conducted a moose test on a Mercedes-Benz A-Class (in 2007) and rolled the vehicle. Mercedes-Benz subsequently recalled more than 130,000 A-Class vehicles sold in Europe and had them retro-fitted with ESC.

What is ESC and why is it important?

Electronic Stability Control (ESC) – is a system to keep a vehicle going in the direction the driver wants it to go, which is usually on the road and rubber side down. ESC can be thought of as anti-skid control, and it primarily corrects understeer and oversteer.  Understeer is when you run wide around a corner, needing to wind on more and more steering lock to no or little effect.  Oversteer is when the back of the car wants to overtake the front. 

How does ESC work?

ESC uses wheel speed sensors to determine how fast each wheel is travelling, then a lot more sensors such as roll, yaw, throttle position, steering wheel angle and more to figure out whether the car is going where the driver wants.  The on-board computers then apply the brakes to one or more of the four wheels to correct the vehicle’s direction. 

For example, if you’re understeering it may apply the brakes on the inside wheels and release those on the outside slightly, thereby tightening the vehicle’s turning radius. In an oversteer situation it will brake one or more of outside wheels. Generally, if the steering wheel is turned the car will try and respond to that direction, so here’s some advice – look where you want to go, and keep the steering wheel turned where you want to go. 

In extreme cases stability control can also cut the throttle, despite the accelerator being floored.  It also uses traction control (below) to help it do the job where appropriate, for example to prevent fishtailing in powerful rear-wheel-drive cars.

The official, generic name is ESC, or Electronic Stability Control (or sometimes ESP, Programme).  Manufacturers have all sorts of other names such as VDC, DSC, ASC… usually some combination of Dynamic, Control, Vehicle, Active, you get the idea. It’s all the same thing, as there are only a few automotive electronics manufacturers that resell to all brands.  However, the effort that each car manufacturer puts in to calibration and design varies quite considerably, so the electronics tend to be much more effective in the more expensive vehicles. 

ESC is a wonderful safety technology and if you are buying a new car it is mandated by law. If you are safety conscious and buying an older car, buy one with ESC (and side airbags).

Can you turn off ESC?

There are so many variations it is impossible to list them all but, in general:

  • Road cars have an ESC off switch which usually just de-sensitives ESC so that it kicks in later.
  • Sports cars have the same switch, but the deactivation is greater so ESC kicks in even later.   Sports cars are likely to have two, three or even more modes of ESC ranging from fully on, a sports mode with reduced sensitivity, and fully off. Such modes may be manually selected, or there may be overall sports modes which change ESC activation points as well as change automatic gearshift patters and throttle sensitivity. Typically the first ESC off mode is a short press of the button, and the second mode is a long (three-second) press.
  • 4X4s have an ESC off switch which disables ESC. It will also disable engine traction control, but leave brake traction control active – the distinction is important, as you do not want your throttle control restricted.  Typically the same thing happens when the centre diff is locked or 4×4 is engaged, and ESC is almost always disabled in low range. 

ESC is usually re-enabled once the engine is turned off and then on again, or sometimes once a certain speed is exceeded. Exactly what the ESC button does is very much vehicle-dependent.  Read the owners manual for details. The skid-mark icon is now a typical ESC-off button.

While you can turn off or turn down the ESC threshold, for 99.9% of drivers this is one button you should never touch in your car.

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Practical Motoring

Practical Motoring