When the ETC light activates on your dashboard, you might wonder what’s happening. What even is the ETC?
In this guide, I’ll explain what the electronic throttle control system is and why the light may have activated.
Ultimately, there’s no substitute for diagnosis from a skilled mechanic!
Let’s get into it.
- The ETC light turns on when there’s a problem with the throttle control system.
- The root cause might lie with the TPS, APS, ECM, butterfly valve, or ETB motor.
- Don’t drive your car when you have an ETC light on.
- Electronic throttle control problems are usually fairly straightforward for a mechanic to repair.
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What Is The Throttle, And What Does It Do?
The accelerator pedal, commonly called the ‘gas pedal’, controls the throttle. In turn, this sits in the aptly-named electronic throttle body (ETB).
The throttle – so named because it controls the airflow – is a butterfly valve. In very basic terms, it’s a disc-shaped piece of metal hinged across its central line.
The more it rotates, the more air passes it. As more oxygen enters the engine, the ECM sends more fuel to the cylinders. The result is more powerful combustion, increasing your car’s output.
You’ll know (well, you should!) that pressing the accelerator pedal means you speed up. Lifting off means you slow down.
This doesn’t happen by magic! Inside the throttle body, the butterfly valve pivots. The more you push the pedal, the wider open it turns, allowing more air into the cylinders.
But how is your gas pedal linked to the throttle body? That’s where the electronic throttle control comes in.
What Is The Electronic Throttle Control?
The electronic throttle control connects your gas pedal to the butterfly valve in the throttle body.
In the past, cars, trucks, motorcycles, and anything with an internal combustion engine, had a throttle cable or linkage (a physical component ‘linking’ the two). All cars before the late 1980s come with these setups.
This direct mechanical connection means the butterfly valve responds directly to your foot.
You can still see the mechanical throttle cables or linkages on old vehicles and many two-stroke engines, such as those on motorcycles, mopeds, ATVs, etc.
However, these days, mechanical components are being phased out in favor of sensors and electrical circuitry.
The electronic throttle control is a network of sensors and computers connecting your gas pedal to the throttle body.
A sensor measures the position of the pedal. This information is relayed through the ETC system in the ECU. In turn, the car’s computer sends information to the electronic motor powering the butterfly valve.
When it was first introduced in the late 80s, the electronic throttle control had its own module. These days, the ETC is usually integrated as part of the overall ECM (Engine Control Module).
Sensors Contributing To The Electronic Throttle Control
The ETC system compiles data from several sensors. In its simplest form, it requires just the following two:
- Throttle Position Sensor (TPS), measuring the position of the butterfly valve.
- Accelerator Pedal Position Sensor (APS), reading the position of the gas pedal.
However, contemporary cars are much more intricate than this. For instance, the pace at which the butterfly valve responds to the modifications in pedal position can be modified. This is utilized in diverse drive modes, such as Eco or Snow.
Many other systems are hugely dependent on the ETC and its processes. These include cruise control, stability control, traction control, idle air control, links with the Transmission Control Module, and so on.
Thus, there are technically hundreds of sensors playing a part in how the ETC reacts.
What Does The ETC Light Mean?
At a fundamental level, the ETC warning light means the system has a problem.
Something has gone wrong. Taking your car to a shop and having them read the OBD II codes should reveal the root cause.
In most cases, the electronic throttle control light comes down to one of only a few possibilities. Thankfully, this means it usually is relatively easy to fix.
What Causes The Electronic Throttle Light To Come On?
Here are some of the most obvious causes when the electronic throttle light illuminates.
Clogged-Up Butterfly Valve
The butterfly valve can clog up over time. This blocks off the air that should be flowing past it. It may even be so severely jammed that the motor can’t open it at all!
The butterfly throttle valve is still part of the ETC system. That’s why you might be seeing the electronic throttle control warning light.
How To Fix
Remove the throttle body from the car. (If you don’t know what a throttle body is, get some reliable help!)
Use brake cleaner (or a similar substance) to spray the plate, removing any dirt, debris, or soot.
Put it back on the car, don’t forget to connect all the bolts and plug it in again.
Has that fixed your problem? I encountered this situation myself a few years ago, and it worked for me.
A bottle of brake cleaner should be less than $10. You can get it from any hardware store.
Breaking Butterfly Valve Motor
The valve inside the electronic throttle body is powered by a motor.
Obviously, if this motor fails, it can’t rotate and will remain in an almost-closed position.
Because the throttle position sensor (TPS) data doesn’t correspond to the accelerator pedal position sensor readings, the ETC light comes on.
How To Fix
When faced with this issue, it’s time for a new electronic throttle body.
The part might cost about $250, with another $80 for labor.
Faulty Throttle Position Sensor
The TPS is a sort of verification device. It checks that the butterfly valve behaves as the ECM tells it to.
If it stops working, the ETC will detect a discrepancy between it and the rest of the system. As a result, the warning light illuminates.
You’ll likely notice additional symptoms if the TPS is on the way out. For example, the engine’s revs will probably jerk and surge.
How To Fix
Depending on your car, you might be able to replace just the TPS. Including labor, expect to pay $100 to $200 for a new one.
Sometimes, you need to replace the entire ETB, costing $300 to $400 (including labor).
Faulty Accelerator Pedal Position Sensor
The accelerator pedal position sensor records how far you’re pushing the pedal (if at all). The ETC uses this information to open or close the electronic butterfly valve.
When this sensor is on the way out, readings will be random and intermittent. This confuses the system, so the warning light switches.
Like with the TPS, you’d also notice strange additional symptoms from your engine.
How To Fix
If this is identified as the root cause of your ETC light, you need a new sensor.
Budget around $200 (plus or minus $100) for this job, including labor. The cost of parts varies hugely depending on your make and model.
Let’s hope it doesn’t come down to this. It’s rare but possible.
The ECU is a broad term for your car’s electrical ‘brain’. It comprises tens (if not hundreds) of individual modules, each comparing data from many more sensors.
The ETC typically forms a portion of the ECM, the Engine Control Module. It is in charge of examining the data received from different sensors and transforming it into directions for the butterfly valve engine.
On occasion, things can go wrong with these computers. These are usually down to either damage or tampering. Manufacturer error (in which case there should be a recall) is also a possibility.
How To Fix
You either need reprogramming or a new module. Either way, you’ll need expert help from auto electricians.
Reprogramming or a replacement module will be in excess of $600 – possibly over $1,000.
Can You Drive When The ETC Light Is On?
You shouldn’t – it’s a bad idea.
If your car completely loses its connection between the pedal and the throttle, you’ll suddenly have no control over the engine.
This makes it a perilous situation, as improbable as it is.
On top of this, the air-fuel ratio won’t function as it should. This often leads to internal dirt and damage, causing further (expensive) issues.
Try cleaning the throttle body plate, as I mentioned above. In some cases, this might fix the issue.
Otherwise, you could either go to a mechanic (which I recommend!) or order the parts to your home. If you know your way around cars, you can probably replace them yourself.
Always take extra care when working with electronics. Remember to disconnect the car’s 12-Volt battery!
Failing that, you could always ask a knowledgeable friend for some help!
Stay safe out there, and if your ETC light comes on while driving, it’s best to pull over and get help!