Reduced Engine Power Warning And Check Engine Light

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.

Electronic Throttle Body can cause reduced engine power.

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!

Electronic Accelerator Pedal




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15 comments to Reduced Engine Power Warning And Check Engine Light

  • harlinwolf

    My s-10 pulls while accelerating..changed fuel filter but still does it. what else could it be?

    • Frankie

      A fuel filter would have nothing to do with the truck pulling to one side or the other. You either have a front suspension part gone bad, or a broken motor mount. Put the truck in drive with your foot firmly on the brake pedal and give it some gas. Have someone look at the engine to see if it is moving excessively.

  • Ray Thornton

    I have a 2003p1125 GMC Yukon xl with about 143000 miles. We are getting a p1125 code and having reduced engine power. We have replaced the throttle body, app sensor, and wiring to throttle body, but code still comes up and reduced engine power. What else can we do?

    • ProTech

      There is another part on your vehicle which controls the functions of the throttle body and communicates with the PCM accordingly. That part is called the TAC module (Throttle Actuator Control). It is located on the firewall. That is what most likely needs to be replaced on your vehicle. It does not require any programming, so it is a part you can replace yourself.

  • Robert De Leon

    I just bought 2006 4.8 Siverado and wash the engine yesterday then the Reduced engine light came on, after 15 minutes of driving and restarting then engine it went away.
    Should I worry or was the cause for washing the engine?
    Thanks Robert De Leon

  • Eddy

    My 2005 Chevy Equinox while we were driving started showing the battery light, slowly after a lot off more warning lights came. Then my accelerator didn’t work,,then it shut-off. My battery was dead, it was replace since it had warranty, i had the alternator rebuild. Now my car starts but the accelerator moves inside the cabin, but it doesn’t due nothing in the engine.

  • jagger

    I have a 2006 GMC Canyon 4 cylinder engine I changed out the fuel pump once to turn on the truck the engine reduce light came on on the dash and the truck does not have power. I pushed the gas pedal and nothing what else can my truck have it never had a problem til I changed the fuel pump.

    • Billy

      It depends on what codes are stored in the computer. Sounds like your truck has a problem in the electronic throttle system. Maybe a bad accelerator position sensor which is part of the gas pedal.

  • Linton Dixo

    I’m having the problem reduced engine power every time the light comes on my engine goes into a stall to where it doesn’t want to pick up speed

  • Jorge Ramirez

    i also have a 2004 gmc sierra 2500 hd and it keeps telling me to reduce engine power i turn it off for about 15 sec and the code goes away for few hours but it does have a throttle code going on.

  • Billy

    I have a 04 chevy silverado z71 thought I carefully rinsed my engine now when I drive just a little ways my reduced engine power comes on and the truck accelerates on it’s own until I shut it off is this part of the throttle body system as well?

  • Fred

    I have 2003 trailblazers an my reduce engine light come on an if I pull over an shut the truck off for about 10 to 15 teen second an start it back up the light goes off for a while. An the check engine light is staying on now

  • Anonymous

    I have a 2006 Saturn relay 2 and recently the engine light comes on and a message that say reduce engine speed and the van slows down. What causes this?

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