The Enhanced Traction System is an all-speed engine based traction control system used by General Motors Corporation in many of their automobile models. In some models, the driver has the option to disable this system by pushing a button marked "ETS". The system uses sensors to monitor wheelspin and reduces engine speed, upshifts or retards ignition timing to improve traction. The Button is usually located on the gearshift and locks off when the check engine light comes on for any other reason.