The reduced engine power warning message can come on your car or truck. Today’s vehicles are for the most part completely electronically controlled. From every button and switch on the dash down to the ‘fly-by-wire’ throttle control system. Back in the day, before these electronically controlled throttles, everything was cable actuated. You press the gas pedal, and a cable opens the carburetor or throttle body. Now it’s all done through computer controlled sensors and solenoids.
With these added controls, there is even more chance of setting the check engine light on because of trouble codes or problems with these systems. Usually, the only sensor you would have on the previously cable controlled systems would be a throttle position sensor. Now there is an electronic accelerator pedal with multiple sensors, and a completely electronic throttle body with many internal sensors and a solenoid.
All of these need to communicate with each other properly so as to deliver the proper throttle angle input by the driver. The nice thing about this type of system is that it can be even more instant than an actual hard connection by a cable. The bad thing is, when there is a problem in any part of this system, it can render the vehicle literally un-driveable and you will get a check engine light and reduced engine power warning.
There is a multitude of problems that can happen if either the electronic accelerator pedal, or electronic throttle body have an issue. First off, inside the accelerator pedal, there are a couple of position sensors that tell the computer where exactly, or rather how far pushed down, the pedal is. These are known as Accelerator Pedal Position sensors, and most have 2 of these sensors.
A problem that occurs often with the accelerator pedals is that the correlation between sensor 1 and 2 is off. This will set a trouble code and often times limit input by the driver to avoid engine damage. You will see the ‘Reduced Engine Power’ message on the dash and the check engine light will most likely come on. Usually this problem just requires replacement of the pedal assembly, although there have been wiring problems on some makes and models.
Now, with the throttle body, there can be similar problems and problems that are unique to just the throttle body. They also have a couple position sensors inside it and can have the same correlation error, but also a few added things as well. The actual solenoid that drives the throttle blade can have errors too. Also, the control portion that understands the commands sent from the computer can fail as well. This is usually called the TAC system, or Throttle Actuated Control. There are performance errors, position errors, and many other things that can go wrong inside the throttle body. Even allowing the throttle body to get excessively dirty with carbon build-up can cause issues. Unstable idle, or stalling can occur easily with these problems.
Replacement of the throttle body is required most times with any of the above listed problems. A cleaning can sometimes help the stalling or low idle issue, but if there is a code set, it is going to need replaced. There are many, many service bulletins that address all of these problems, so taking your vehicle to the dealership is always recommended when you have an issue like this to get it corrected quickly and accurately.
Vehicle maintenance plays a big part here, so keep up on it and you should have little or no problems at all!
Below are a couple pictures of an electronically controlled throttle body and accelerator pedal. You’ll notice there are no provisions for cables, just electrical connectors on each component. Welcome to the electronic age!