Technical
Understanding vehicle stability control Gaining control before it’s too late The goal of all electronic stability control systems is simple: prevent side skidding and the subsequent loss of control that side skidding creates. The topic of vehicle stability control (VSC) is often misunderstood. This article sheds light on how the system works along with tips on diagnosing issues relating to this electronically controlled vehicle handling technology. By Jeff Taylor
J
ust what is stability control? And why do we have it? My GMC pickup caught me totally off guard when I was going up a familiar hill on a damp morning recently. I was accelerating normally when the rear end started to break loose. Before I could react, however, the StabiliTrak light started to flash, the rpms dropped, and I could hear the anti-lock brake system (ABS) pump running and the solenoids cycling. I never hit the brakes but my immediate reaction was to let off the gas... but by then my truck had already returned to the direction that I’d always intended. Almost before I lost control, I had it back again. This was my introduction to electronic stability control (ESC). ESC goes by many different names: Mitsubishi calls its system active skid and traction control (ASTC); Toyota, vehicle stability control (VSC); Volvo, dynamic stability and traction control (DSTC); Jeep, electronic stability control (ESP); Honda, vehicle stability assist (VSA); Infiniti, vehicle dynamic control (VDC). These are just a few of the vast number of names that the manufacturers have given
their ESC systems. But the goal of all ESC systems is simple: prevent side skidding and the subsequent loss of control that side skidding creates. ABS and traction control systems control the vehicle along the longitudinal (front-to-back) axis, while ESC controls the vehicle along the lateral (side-to-side) axis. Government data has shown that vehicles equipped with ESC were involved in approximately 35% fewer severe collisions that involved loss of vehicle control versus non-ESC equipped vehicles. ESC anticipates dangerous situations even before the vehicle goes out of control and is so effective, in fact, that the government mandated ESC on new vehicles built after 2012. ESC is not a modern-day technology. Developed by BMW, Mercedes-Benz, Bosch and Continental Automotive Systems in the late 1980s, it made its road debut in 1995 on the S-Class Mercedes-Benz. Other manufacturers followed quickly. GM/Delphi introduced StabiliTrak as an option on some Cadillacs in 1997. Ford launched AdvanceTrac in 2000. By the mid-2000s most manufacturers offered some form of ESC. Many ESC-equipped vehicles have lots of miles on them now and technicians are being
26 | ASP October 2017
