electronic throttle control light

Electronic Throttle Control Light: What Should You Do If It Comes On?

In a modern car, almost everything is electronic. For the older generation out there, most systems we grew up seeing in their mechanical glory have gone electric or electronic in the near past. But this comes with its own share of problems. Electronic Throttle Control Light is a way to hint at these problems. But what makes it illuminate?

When the electronic throttle came in, it replaced the cable-actuated throttle body that many of us were used to seeing in cars. The arrival of the electronic throttle body improved communication between the throttle and the engine management system. But is the electronic throttle control light a drawback that stems out of this shift towards electronics? Well, the short answer is no. We will also learn about this in detail.

But before we dive into this deep realm, we need to understand what a throttle body does and how it can fail? These are the potential triggers for the illumination of the electronic throttle control light. Hence good knowledge about these can go a long way in understanding the electronic throttle control light.

What Is A Throttle Body?

As its name clearly hints, the throttle body is a mechanism that allows the driver to control the amount of air that passes into the engine. This predominantly mechanical device sits between the intake filter and the intake manifold.

It has a flap that opens and closes depending on how hard the driver is pressing on the gas pedal. When the driver goes pedal to the metal, the throttle body opens completely, allowing maximum air to flow into the engine.

A throttle position sensor reads the position of the throttle and helps the fuel injection system inject sufficient fuel into the engine. Thus, the throttle body directly affects the performance of your vehicle. The electronic throttle control light mostly comes on when there is an issue with the throttle body.

Here is a list of all parts of the electronic throttle body and their functions.

Butterfly Valve

This perhaps is the most important part of a throttle body. This valve is what opens and closes when the driver stomps on the gas pedal. The valve is actuated directly by a cable in the case of mechanical throttle bodies. The pressure on the gas pedal directly affects the opening of the butterfly valve in these cases.

In an electronic throttle body, the butterfly valve is operated by a tiny electric motor that takes input from the engine control unit. The ECU sends these signals based on a myriad of inputs, primarily the gas pedal position. Throttle body opening is determined by the ECU and then communicated to the electric motor that actuates the butterfly valve.

The butterfly valve has three major positions. The first one is the fully open position which is achieved when the driver pushes the gas pedal all the way down. This is when maximum air flows into the engine along with the corresponding amount of fuel. The second position is the resting closed throttle position. This can be adjusted by a small screw near the gear that operates the butterfly valve. This directly governs the idling speed of your car.

The third position is the absolute close throttle position, this is when it is completely closed with no room for air to pass. This position is usually achieved only when the throttle valve position learning is conducted by the ECU. This happens mostly after the throttle body is cleaned. Once the learning is completed, the throttle body reverts to the resting closed position.

Every other part of the throttle body revolves around the operation of the butterfly valve. This makes it the center point which we have to know. Especially when we are trying to learn about electronic throttle control lights.

DC Motor

This is a little motor housed under the butterfly valve and it is responsible for the opening & closing of the valve. The motor takes inputs from the ECU to determine how big an opening it should facilitate. The motor is connected to the butterfly valve via small gears.

The DC motor takes its power through two small pins that jut out of it. They lead to the final connection of the electronic throttle body that runs to the ECU, where it gets its power from.

Return Spring

As we have experienced, the gas pedal always returns to its original state once we lift our foot off it. This is the closed position of the throttle sensor. The butterfly valve gets a return spring that helps the throttle go back to the safe, closed position once the driver input is taken away.

This gives us two advantages. First and foremost, it enhances safety. If by chance, the motor fails, the spring will ensure that the valve gets closed. If the butterfly valve is closed, the ECU gets this information and instructs the fuel injection system to not send any fuel to the engine. This will cut down the power and prevent an accident.

The second advantage is that the automatic closing of the throttle helps you burn less fuel. The immediate return of the gas pedal and the closing of the throttle disrupt the flow of air, and subsequently, the fuel. Hence, the unwanted combustion of fuel is avoided, saving us more of it.

Coolant Lines

Electronic throttle bodies can throw you an electronic throttle control light if your butterfly valve is restricted. The motion of the valve can be restricted by a bunch of factors but ice is a major reason. If you drive in areas with lower temperatures, the freezing air passing through the butterfly valve can create ice inside the throttle body. This can restrict the motion of the throttle body.

With such a situation in hand, it is imperative to heat the throttle body to ensure smooth operation. Hence, hot coolant is passed through the throttle body through dedicated coolant lines. This will heat up the throttle body, melting away the formed ice. It also doubles as a cooling mechanism for the coolant, though the contribution may not be that significant.

If you remember your elementary physics, you may remember that air is denser when it is cold. Dense air is advantageous to the engine as there is more oxygen to burn per unit volume of air. This helps an internal combustion engine generate more power. This is the very reason, turbos come with intercoolers to cool down the compressed air before pumping it into the engine.

But, if the coolant heats up the throttle body, would it not heat up the incoming air? This will surely reduce the density of the air and reduce the power output. Right? To an extent, it is true. The warmer throttle body can increase the warmth of the air by a bit, that is for sure. But this is not enough to make a drastic difference in the density of the air. Also, the air flows through the throttle body at a high pace. Hence it does not get affected much by the warm throttle body that it touches for a few microseconds.

Throttle Position Sensor

This is yet another important part of the assembly of a throttle body. It is also a major contributor to the problems that trigger the illumination of electronic throttle control light. The throttle position sensor plays its role by reading the throttle position and checking with the ECU to ensure that it is in the right spot.

Diagnose electronics troubleshooting sensor

The ECU gets the data from an accelerator pedal position sensor which reads the position of the gas pedal. It then compares it with the throttle position sensor to ensure there are no discrepancies. If any of these sensors have gone wrong, the misaligned data will let the ECU know. And bam! Here is your electronic throttle control light.

Gas Pedal And Position Sensor

Though technically not a part of the electronic throttle body, the gas pedal and its position sensor are equally important to its operation. The gas pedal, as we all know is a major control element of our vehicle that we interact with.

In older cars with mechanically operated throttle bodies, the gas pedal is directly linked to the throttle body via a cable. As the driver presses the pedal, the cable tightens and opens the butterfly valve.

electronic throttle control light

But in a modern electronic throttle body, the gas pedal is connected to a position sensor. This position sensor reads the gas pedal position and sends this data to the ECU. The ECU then uses this data to calculate the optimum throttle position. And then, as we know, this information is relayed to the throttle body. Any malfunction in this operation can potentially illuminate the electronic throttle control light.

Electronic Throttle Control Light Diagnostics

The electronic throttle body comes with a complex diagnostic system that is used to monitor its operation. The diagnostic software runs in the ECU and takes action if any abnormality is found. Depending on the vehicle and the issue found, the engine may shut off or come back to idle speeds. This diagnostic software is also responsible for turning on the electronic throttle control light, alerting the driver about the issue at hand.

The following video details the fail-safe mechanisms of throttle bodies in Lexus vehicles.

In these cars, if there is an error spotted in the sensors, either the gas pedal position sensors or the throttle body position sensors, the car may revert to its idle state. If there is a discrepancy between the readings of these sensors, the engine shuts off. Any physical object constricting the movement of the butterfly valve is dealt with by shutting off the engine. The same action is taken if the system detects any additional voltage that came from somewhere other than the ECU.

Reasons For Electronic Throttle Control Light Coming On

With enough information on the electronic throttle system and its constituent parts, we can now move ahead and learn more about the electronic throttle control light. It comes on to alert the driver about a malfunction in the electronic throttle system. This gives an early warning about an issue and gives room for the driver to act.

The electronic throttle control light looks like a short lightning bolt flanked by two inward curved vertical lines. It may be in red, orange, or yellow color depending on the make and model of the vehicle. Just like every other warning light, it will turn on for a short while starting your car to ensure that it is working.

But it does not mean that every car out there will have an electronic throttle control light. For the most accurate information, your owner’s manual is your best friend. If this light stays on even after starting your car, there will be an underlying issue. This can be pinpointed by using an OBD II reader. Here is a good one we found on Amazon.com.

With the familiarization of the electronic throttle control light done and dusted, let us dig into the causes that may turn it on. Here is a comprehensive list of all causes that may end up illuminating the electronic throttle control light.

Electronic Throttle Control Light Causes #1: Faulty Throttle Position Sensor

We have talked about this before. The throttle body sensor is one of the key components in an electronic throttle system. A failure in this sensor can send wrong data about the position of the butterfly valve. This can completely make the operation go for a toss. Depending on the vehicle, the engine may go into its idle state and the system will throw an electronic throttle control light.

Electronic Throttle Control Light Causes #2: Faulty Accelerator Pedal Sensor

This is yet another sensor that the electronic throttle banks on. This sensor reads the position of the gas pedal and relays this info to the engine control unit. As further calculations are made based on this data, a wrong reading can have a cascading effect on the throttle body operation, as well as the fuel injection.

Diagnose electronics troubleshooting

A wonky accelerator pedal sensor can be one reason for the electronic throttle control light to come on. But it can also be affected by any malfunction in the accelerator pedal module. Similar to the throttle position sensor, the engine may reset to idle, depending on the vehicle. But it will surely throw the driver an electronic throttle control light.

Electronic Throttle Control Light Causes #3: Stuck Throttle Body

As we talked about it before, a stuck butterfly valve can completely hamper the operation of the electronic throttle body. As a part of the diagnostic process, the system recognizes this situation and illuminates the electronic throttle control light.

The physical objects that obstruct the valve’s movement can be anything but carbon build-up are the most common of them. It plagues many old cars. If the carbon build-up is completely blocking the valve, you will have to clean it up at a garage. If it is too late for even that, a new throttle body may be needed to stop that electronic throttle control light from lighting up.

Another prime candidate that blocks the valve is corrosion. The throttle body is made of metal and is prone to corrosion. If water enters the throttle body, it can corrode the same from the inside. This may be around the valve, or near the shaft. In both these cases, you will end up with a stuck valve, and of course, a brightly illuminated electronic throttle control light.

This is not it. In some rare cases, even dirt makes its way into the throttle body. If the car has been flooded, for instance, there are high chances that the throttle body carries dirt. These can not only block the valve and trigger the electronic throttle control light but also damage the engine. So, in these situations, it is better to let a mechanic carry out a thorough cleaning of the components before turning the engine on.

Electronic Throttle Control Light Causes #4: Electrical Issues

Yet another common cause for the electronic throttle control light to come on are electrical issues. As the electronic throttle works based on the electrical signals from the ECU, any fluctuation in that can alter its operation. In some cases, external magnetic or electrical fields may also interfere with its operation. But most modern cars are equipped to combat this.

electronic throttle control light

Improper electrical signals are sent by the ECU in some uncommon situations. The first of which can be loose connections in the wiring or spliced/corroded wiring. These faulty wiring can trigger erratic signals to travel from the ECU to the throttle body. This is easily picked up by the diagnostic system, turning on the electronic throttle control light.

Another reason for these is mechanical failure. A mechanical failure in the link with the gas pedal can turn on the electronic throttle control light. It can send intermittent signals or cause a complete loss of signal from the ECU. This turns also true for the situations in which the gas pedal module is faulty.

Symptoms Of Electronic Throttle Control Light Problems

The electronic throttle control light is not a problem on its own. It is merely an indication of a problem that lies underneath the skin of your car. But, apart from the electronic throttle control light, there are a few more symptoms that you can look for. Having an eye, or ear, for these can help you find out issues even before they turn worse.

Here is the list of all issues that may accompany the electronic throttle control light.

1. Engine Stalling/Misfiring

The stalling or misfiring of an engine is not an exclusive issue that comes with electronic throttle control light. A bunch of issues can cause it and throttle body issues are some of them.

2. Rough Idle

If your vehicle idles in a rougher than usual manner, you may have all reasons to suspect a throttle issue. In most cases, it will be accompanied by the electronic throttle control light, making the issue quite obvious.

3. Lack Of Smooth Acceleration

If there is sensor damage or a physical blockage in the throttle body, you cannot expect the vehicle to accelerate smoothly. The vibrations and rough noises are a dead giveaway, and so is the electronic throttle control light turning on.

4. Reduction In Fuel Economy

If the gas pedal and the throttle are not communicating with each other properly, it is bound to have a cascading effect on the remaining systems. One of the most affected systems includes the fuel injection system, as it is directly impacted by these erratic signals. This can lead to a drop in fuel efficiency.

low fuel economy

5. Black Exhaust Smoke

This too can be caused by different reasons, including oil leakage into the cylinders. But an electronic throttle control light-inducing issue can also increase pollution, especially in older cars.

car exhaust smoke

6. Unable To Start Engine

If you find it difficult to start the engine or are not able to start it at all, it can be a throttle-based issue. The improper signals from the throttle control system may not be sending the right amount of fuel and air required to crank the engine. Of course, there are other issues including a faulty starter motor, drained battery, fuel pump issue, etc that can have the same effect.

7. Car In Limp Home Mode

Most cars are equipped with this fail-safe mechanism called limp-home mode. This comes into play when the ECU of the vehicle detects an issue. It prevents the vehicle from going beyond a certain speed to avoid any further damage. The car may go into the limp-home mode for several reasons but the presence of a lit-up electronic throttle control light can confirm the presence of some issue with the throttle.

Summary On Electronic Throttle Control Light

The electronic throttle control light is quite a handy warning symbol that gives us an early heads-up if anything throttle-related is wrong. But it is necessary to understand what causes it and what can be done to prevent it. It is also important to treat it with the respect it deserves.

Just like every warning signal in a car, ignoring this warning can have catastrophic effects on the vehicle. A small issue that can be avoided may grow into a larger, more expensive issue.

The electronic throttle control light is more of an umbrella warning for a number of issues that we detailed above. So, it is necessary to use an OBD II reader to pinpoint the exact issue. This will help you or your mechanic remedy it with the right fix.

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