Electronic Throttle Control: Functions, How to Restart, and FAQs

Have you ever wondered why or how your car gets faster the harder you step on the gas pedal?

When you accelerate, different components work together to get more air into the engine, causing a chain reaction within the engine. The entire process is thanks to the throttle system, with the brains of the operation being the electronic throttle control.

What Is Electronic Throttle Control?

Older engines had mechanical linkage or a throttle cable connected to the butterflies in the base of the carburetor or the throttle plate in the mechanical throttle body. You step on the gas pedal to open the throttle and allow air to flow into the engine to mix with gasoline on its way to the cylinders. To go faster, you step on the pedal harder to open the throttle wider, allowing for more air and power.

However, the introduction of electronic throttle control (ETC) added a different layer to how cars work nowadays.

Electronic throttle control (ETC), or drive-by-wire, allows vehicles to send electronic signals to the throttle to open it (instead of mechanically opening it).

The process now goes, when you step on the pedal, the redundant position sensors in the accelerator pedal send the pedal’s position to the ECM/PCM, which sends pulses to the throttle body electric motor that operates the butterfly plate. There are redundant throttle plate sensors in the throttle body for feedback so the PCM will know the throttle plate position at all times.

Caution: While there is a weak spring to hold the throttle plate in the closed position as a default, while the key is on, the ECM/PCM drives the throttle plate in both directions – open and closed. Never put your fingers in the throttle body while the plate is open to avoid serious injury.

ETCs have different components that make up the system, including the accelerator pedal, the ETC module, and the throttle body.

Before, a throttle cable was attached to the pedal to open the throttle. It’s been replaced by the accelerator position sensor (APS) to give the exact position of the pedal, thus transmitting the signal to the ETC module.

Benefits of Electronic Throttle Control

The ETC offers several advantages, including idle air control, engine control, and better transmission RPM management.

Idle Air Control

Idle speed was once handled by stepper motors with a pintle bypassing the throttle plate. The ETC just automatically changes throttle plate angle.

Note: The electronic throttle body takes the place of the Idle air control valve. No ETC-equipped vehicle has an IAC valve.

The electronic throttle body takes the place of the Idle air control valve. No ETC-equipped vehicle has an IAC valve.

– Richard McCuistian, ASE Certified Master Automobile Technician

Engine Control

With the help of other sensor inputs like the VSS (vehicle speed sensor), individual WSS (wheel speed sensor), and shift position, ETC systems can control engine output to reduce wheel spin on low-traction surfaces like snow, ice, or gravel.

At the same time, the  ETC can modulate engine power output to improve vehicle stability at higher speeds by monitoring the VSS, WSS, g-force, and yaw rate sensors.

Lastly, the ETC can cut engine power in case a crash is calculated to be unavoidable using input from the pre-collision system (PCS).

Pro Tips are nuggets of information direct from ASE-certified automobile technicians working with CarParts.com, which may include unique, personal insights based on their years of experience working in the automotive industry. These can help you make more informed decisions about your car.

Pro Tip: Unlike pre-ETC systems that needed extra hardware under the hood for cruise control, the ETC system simply uses the existing inputs to the ECM/PCM along with the steering wheel buttons the driver uses to set vehicle speed. No extra hardware is needed for cruise control on an ETC equipped platform.

Transmission RPM Management

The ETC can use RPM, shift position, VSS, and other sensors to match the engine speed with the selected gear. Generally, the driver modulates this in manual transmission vehicles, but an ETC vehicle can perfectly sync throttle blips with downshifts for faster engagement and smoother power transfer. Some platforms will feather the throttle during shifts for a smoother shift feel, and this can be done electronically.

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Why Is My Electronic Throttle Control Warning Light On?

An illuminated electronic throttle control light indicates a problem with the engine’s fuel and air intake or an issue with the throttle system.

Effects of Driving With a Bad Electronic Throttle Control

The effects of driving with a faulty electronic throttle control include sudden acceleration, reduced fuel efficiency, and engine shutdown, among others.

Sudden Acceleration

A faulty electronic throttle control could lead to sudden acceleration, usually due to a malfunctioning accelerator pedal sensor picking up incorrect signals. It can also be caused by a faulty input between the brake and the cruise control system or a throttle plate stuck open.

Regardless of what’s causing it, sudden acceleration is dangerous. So it’s best to take your vehicle to a mechanic as soon as possible if you notice this issue.

Reduced Fuel Efficiency

The throttle system helps optimize fuel efficiency, so any form of malfunction or damage could lead to increased fuel consumption. This can cost you a lot in the long run as you’ll constantly have to refill your vehicle, more so than usual.

Engine Shutdown

Again, the throttle system opens the throttle for better efficiency and improved performance. Once it malfunctions, it could affect your engine’s performance and may lead to the sudden shutting down of the engine.

This is dangerous to drive with, especially on busy highways, because there’s a chance you’ll end up in a rear-end collision, especially if the car behind you is driving close.

Safety Issues

Any form of damage or malfunction within a vehicle can be considered a safety risk, one way or another. This rings especially true if it’s something as significant as the throttle system because it works with the engine and fuel. The redundant sensors in the accelerator pedal assembly and the throttle body are specifically in place to mitigate possible issues with the ETC.

Illuminated Check Engine Light

As mentioned, the ETC warning light illuminates when it detects any signs of malfunction within the throttle system. The same rings true for the check engine light because it could affect different parts of your vehicle.

Note that many vehicles have a dedicated specific warning light in addition to the check engine light. The light for the electronic throttle body looks like a cutaway throttle body or a wrench.

How to Reset Electronic Throttle Control Manually

You can use an OBD2 scanner to reset the ETC light. To do so, you’ll have to clear the fault code memory in addition to fixing the problem that caused the warning light. But keep in mind that if the ETC system is malfunctioning, more needs to be done than just resetting the system.

Some common triggers include a faulty throttle control sensor, a faulty accelerator pedal position sensor, and a stuck throttle body.

Of course, it’s still best to take your vehicle to a mechanic for a better diagnosis. Minor repairs should only cost a few dollars to fix, while more serious problems like the ones listed above could cost between $100 and $800 to fix.