Back in the day, thirty-plus years ago, the gas pedal in your car was physically attached to the throttle on your engine. When you push down on the pedal, a cable running from the pedal to the engine compartment pulls open the throttle, letting air and fuel into the engine to provide the needed acceleration.

But those days are long gone. In today's computer-controlled engines, the action of the throttle is regulated by electronic sensors. This system is known as the electronic throttle control (ETC) system. When something goes wrong with the ETC system, you will be alerted to the problem by one or more of the following dashboard warning lights:

    • The ETC warning light (a lightning bolt with reversed parentheses on each side)
    • A wrench symbol
    • The check engine light

Join us for an insider's view of how the electronic throttle control system works, the benefits of electronic throttle control, what causes the electronic throttle control system to fail, and the cost of fixing the electronic throttle control.

How the electronic throttle control system works

The classic cable-controlled throttle systems worked fine in most cars until tough emissions control and fuel economy standards made these mechanical connections obsolete in the late 1980s. Super-precise computer controls became the only way to run engines cleanly and increase gas mileage to the mandated levels. The engine control computers developed back then could continuously adjust the air-fuel mixture, based on your car's speed, the outside temperature, how much power you needed at a given moment, and various other inputs. These "drive by wire" ETC systems have steadily evolved since those early days. They are much more sophisticated today than ever before.

Instead of an old-fashioned cable, your ETC system uses a sensor attached to your accelerator pedal. The sensor sends a signal from the pedal to the engine computer. Based on how far you press down on the pedal, the sensor tells the electronic throttle in your engine to increase the amount of air entering the engine by a comparable amount. This increased airflow is measured by an engine sensor that tells the computer to provide more fuel to mix with it. The increased air-fuel mixture is cleanly burned inside your cylinders, instantly providing the power your foot on the gas pedal has requested.

Today's electronic throttle control systems do much more than accelerate your vehicle. Your ETC system can also:

    • Control your car's idling
    • Manage your cruise control
    • Cut the power when your automatic emergency braking is activated
    • Assist with transmission functions like sport and winter modes

The benefits of electronic throttle control

Your electronic throttle control is a sophisticated electronic system that comes with many benefits for today's drivers:

    • Fewer moving parts mean less wear and maintenance is needed
    • Your vehicle is easier to operate
    • Improved drivability
    • Extremely precise cruise control
    • Keeps you safer with stability control
    • Lower emissions for cleaner air
    • Better fuel economy

What causes the electronic throttle control system to fail?

The technology behind your ETC system is based on the precise computer control of your engine's air-fuel mixture. This assures you of smooth engine operation and power when needed, low emissions, and the best possible fuel economy. When there is a problem with your electronic throttle control, your engine cannot get the correct amounts of fuel and/or air when needed. A variety of different factors can cause these problems:

    • Electrical or electronic malfunctions in the ETC or engine computer
    • Dirt in the throttle
    • Wear and tear of the moving parts
    • Blockage in the fuel system
    • Vacuum leak that affects proper airflow

When these ETC-related issues occur, your computer will usually produce a trouble code that will point your mechanic toward the correct diagnosis of the problem. Once the problem is fixed, the code will be cleared and the system will reset.

How can you tell that your electronic throttle control system is failing?

Your electronic throttle control is a technically complex system, and there can be problems that cause your ETC light to come on. Remember that we are dealing with your engine's computer controls; your throttle control is an important safety-related system. For your own protection, and that of others in your car and around you, problems with your ETC should be diagnosed and fixed by a professional mechanic. Let's zoom in on some common symptoms of ETC problems, and what to do about them:

A major reduction in your gas mileage

If you notice that your car is not going as far as it usually does on a gas tank, it could be a sign of a problem in your ETC system.

What to do: Make an appointment with your repair shop right away. You want to stop wasting fuel - and money - as soon as possible! Your mechanic will use a code reader to check the engine computer and diagnose your car's problem. A faulty ETC can send incorrect signals, causing your vehicle to burn too much fuel. Your electronic throttle control can then be repaired to resume normal operation - and give you the fuel economy you expect.

Stumbling or hesitation as you accelerate

Damaged electronic throttle control can result in hesitation or stumbling when accelerating.

What to do: Have your car towed to a repair shop immediately - driving is unsafe! The trouble code in the computer aims your mechanic toward a correct diagnosis, and repairs to your ETC system can be made.

The operation of the throttle becomes erratic

This can be very scary! It is caused by an intermittent loss or disruption of the electronic signal from the gas pedal to the throttle. Your throttle will operate normally sometimes, but at other random times, it will accelerate either not enough, or too much. Both situations are extremely dangerous, and either one could cause an accident.

What to do: Pull over as soon as it is safe, and then call a tow truck. Your electronic throttle control system must be repaired before you can drive it again.

Your car gets stuck in "limp home" mode

You notice that your car is suddenly unable to accelerate beyond a certain speed, forcing you to drive it at a slow pace.

What to do: Your vehicle's computer has switched to "limp home" mode. Your car has a serious ETC problem, and it runs this way so that no further damage can be done. If your mechanic is nearby, you should drive it directly to the repair shop. If not, a tow may be necessary. Finding the cause and making repairs should return your car to normal operation. Don't wait to fix it when this happens!

Can you drive with the ETC light on?

In some specific situations, you can, such as when your car runs normally but has a bad fuel economy. But if you can no longer control your car's acceleration, you must have it towed to a repair shop immediately. The consequences of losing control of your vehicle are too terrible to think about. There's absolutely no upside - and plenty of downside - to driving a car with serious ETC-related drivability problems.

How do you fix your electronic throttle control system?

The key to fixing the electronic throttle control system is to properly diagnose the system, and then identify the precise cause of the problem. Once this has been achieved, the appropriate parts can be repaired or replaced, returning your electronic throttle control system to proper operation. This can involve new sensors, wiring, or even a computer.

To be sure that the problem with your electronic throttle control system is limited to the electronic components, your mechanic should also check out the mechanical parts of your ETC system. Many mechanical issues can produce the symptoms noted above. These things should be ruled in or out and repaired as necessary.

What does it cost to fix or replace your electronic throttle control?

As with many automotive repairs, the best general answer to this question is, "It depends." Your ETC is part of your engine computer and your emissions control system. This means that there is a great deal of variability in figuring an estimated cost, based on:

    • How complex (and time-consuming) the diagnostic process is
    • Whether the problem is limited to one part or several
    • The cost of those parts for your specific vehicle
    • The amount of labor required to do the repairs
    • The labor rate where you have the work done

Depending on your car's year, make, and model, repairing the electronic throttle control system could run anywhere from two hundred dollars to well over a thousand dollars. The best course of action is to call a well-rated repair shop and get a firm diagnosis of your electronic throttle control system problem. Then you will have a better idea of what repairs will cost.

Is it worth repairing your electronic throttle control?

It is worth fixing if you need your electronic throttle control system repaired and your car is otherwise in good running condition. This is because you can't drive your car safely if you don't have control of the throttle.

But if your car is very old, has many miles, is not exceptionally reliable, and the cost of fixing your electronic throttle control system is high, you have a decision to make. Here are some questions to ask yourself:

    • What is your car worth?
    • How many miles are on it?
    • Does your car have any other chronic issues that could soon result in a big repair?
    • Will the brakes or tires need replacement soon?
    • Is it time to cut your losses and get rid of your car now?

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