What is an Electronic Throttle Controller?
Electronic throttle control is a system integrated into the car’s main computer, the Engine Control Unit (ECU). It uses a control module operated by the accelerator pedal and an electronic throttle body (Air Control Valve – ACV) on the engine.
The Electronic Fuel Injection (EFI) system is also controlled by the ETC. All three devices and systems work together to provide precise engine speed regulation. When you press the accelerator pedal, the ETC system opens the ACV’s internal throttle, allowing more air into the engine, while the EFI increases fuel flow. This makes the engine go faster.
At the same time, the ECU adjusts the engine valve and ignition timing according to a programmed profile to ensure smooth, powerful engine acceleration.
The ETC also determines the engine speed during warm-up immediately after starting, regardless of the accelerator pedal position. The engine’s idle speed is automatically increased to ensure smooth cold running and minimize the leakage of unburned fuel from the engine to the catalytic converter. In this way, emissions during cold start conditions are kept to a minimum.
Most air control valves have a Throttle Position Sensor (TPS). The TPS sends a signal back to the ECU to ensure that the air valve is responding exactly as the ECU commands it.
In sports and performance cars, the ETC may be designed to include multiple operating modes that the driver can select. These modes may be:
1. The so-called “Normal Mode” is suitable for most driving situations and offers the best fuel economy.
2. “Sport Mode” changes the ETC throttle position profile, resulting in quicker throttle response during acceleration.
3. The next step is “Track Mode.” This is intended to further improve performance.
These alternative modes also include changes to the valve and ignition timing profiles. Of course, the choice of power settings reduces fuel consumption but does not negatively impact emissions. This multi-mode capability increases the driving enjoyment of most car enthusiasts.
Even the smartest ETC can fail. This is where the Throttle Control Light (TCL) comes in to help.
Can I drive with the TCL on? If the Throttle Light is on, it indicates that the problem is intermittent or ongoing, but the car can still be driven. As explained above, the ECU may be limiting the top speed. A TCL “on” condition should be resolved as soon as possible to avoid cumulative damage to other systems in the car. A flashing throttle light (like a flashing CEL) indicates a serious problem that requires immediate repair. If you see these warnings, do not drive your vehicle except to a safe location on the side of the road.
Note: Some ETC errors may result in reduced air-fuel ratio control. If too much fuel enters the engine during such a failure, incomplete combustion can occur.
This can cause excess unburned fuel to enter the catalytic converter in the exhaust system, causing localized extreme temperatures. Overheating of the converter can damage or even destroy the insides of these expensive devices – just one of the important reasons why it is always recommended to immediately heed any illuminated TCL or CEL warnings.