Mechanical Throttle Control v. Electronic Throttle Control

Before the advent of the electronic throttles, vehicles were equipped with mechanical throttles. In a mechanical throttle control system, the accelerator pedal is connected directly to the throttle by a cable. When a driver is not stepping on the accelerator pedal, the throttle is closed. When the driver steps on the accelerator pedal, the cable pulls open the throttle.

Electronic throttle control systems allow a vehicle’s throttle to essentially be controlled by sensors connected to a computer.

Toyota’s electronic throttle control system is known as ETSC-i, or Electronic Throttle Control System – with intelligence. The ETCS-I system operates by using two redundant sensors to sense the accelerator pedal position. These signals are read by the Engine Control Module (ECM). The ECM also receives signals from two redundant throttle position sensors. Based on the readings from these wires, the ECM sends a signal to open the throttle.

Toyota began introducing ETCS-i in some of its Lexus and Toyota vehicles sold in the United States as early as 1998. By 2004, most of the Lexus and Toyota models available in the United States were equipped with ETCS-i. By 2006, every Lexus and Toyota model available in the United States was equipped with ETCS-i. By 2007, every Scion model available in the United States also had ETCS-i.

Southern Illinois University engineering professor David Gilbert testified before a congressional panel in February 2010 that he was able to essentially short-circuit some of the sensors in Toyota’s ETCS-i and create a Sudden Unintended Acceleration event for which no diagnostic trouble code, or fault code, was recorded in the vehicle’s ECM memory.

 

Toyota Recall Timeline

Sudden Unintended Acceleration

Throttle Control Problems

Electromagnetic Interference

Recalled Toyotas

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