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!
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119 Comments on "Reduced Engine Power Warning And Check Engine Light"
2007 GMC Sierra 1500 has had TPS, TAC,ECM and Throttle body has been replaced and ground wires ran to all, Problem is the truck will start up and go into REP and have codes for TP/TPS not responding, can clear codes at times and it will drive fine then next day start throwing codes again, I have ran test on TPS and it shows getting proper power when codes cleared, then ran test when in REP and it shows no power to TPS…Owner is ready to add some lead into truck, has anyone else had this problem and found the cure ?
I replace the throttle pedal in the engine light still come on saying throttle pedal
I just went through replacing throttle body, connectors, accelerator pedal sensors and throttle position sensor, and that didn’t fix it, BUT I unplugged the AIR Solenoid on top of engine and that was the problem, we’ll be tracing down those wires and connectors tomorrow. Hope that helps
Hi Beth… what was your final conclusion… I’m having the same problems, 04 Yukon XL
I hav 0y chevy 5.3 not drivable with pedal plug n wen started wont idle runs bout 3500 rpms and reduced power light comes on and it shuts down wen pedal unplugged it idles at bout 800 rpms but misses very bad ive replaced coils and wires no diff
My 2007 gmc Sierra Will go into low engine power. I turn the truck off and on five minutes it will be drivable again what would cause this
Unplug the Air Solenoid and see if that fixes it, if so there’s your problem.
Top off your coolant. It will fix reduced engine power and check engine light. Worked on My 2016 Malibu
I have a 07 Chevy Silverado new body still have replace throttle position sensor on throttle body that whole pedal in floor board plugs wires coil packs an stuff like that my truck has no power an is shifting hard into 2nd gear I was wondering if it could be that rear speed sensors causing this problem or maybe catalytic converters stopped up or what could I do to fix this?
Whatcause múltiples y sensor reading vas but work right most time
2011 Chevy Silverado reduce power light is on and drives slow
Went driving yesterday. Stopped at 3 different places all close and last place we stopped and turned off car. 10 minutes later we came back out and started up car started driving away and we lost all power and check engine light and transmission light came on and car wouldn’t move.
Can’t find out what’s wrong any ideas??
My vehicle would randomly go into a low power mode. 2003 chevy silverado. Had three throttle bodies, accelerator pedal and throttle actuator control changed. still had a low engine power problem. Finally solved it by repairing a bad battery ground. There are two cables coming from the neg. terminal of the battery. The larger one goes to the engine. I ignored it. The smaller one goes to a body to frame bracket. This was my problem. Although it was secure, it was rusted. After removing the wire and thoroughly cleaning, that is scraping the paint off of it. I re-attached the wire. Problem solved. In addition I happen to have some “KOPR-SHIELD” its a T&B product CAT# CP16. Its a conductive anti-corrosion surface treatment. You do not need to use it but, if you don’t, after re-attaching the wire coat the entire terminal with grease to prevent moisture seepage from causing it to rust. I haven’t had a problem since I repaired it. Walter.
Thanks Walter that seems to have been my problem it worked for me but my positive cable needed tighten
K I replaced my egr valve, throttle position sensor and still it idles high at times it stalls out when driving, loss of power, and at times the reduced power light comes on, and the ABS lights comes on, and check transmission, and cruise control light but that only happens once n awhile but today when driving it the reduced power light came on and I couldn’t go no more the like 10 miles. What could b the problem r what do u think I should try next that would fix my problem.
Low power mode? Really? Stupidest thing I’ve ever heard of!
Where did you see that ?
I have a 2012 Chevy Equinox. I have gotten the fuel rail senor, and catalytic converter replaced at the dealership. My check engine light still comes on randomly as well as the message that says “reduced engine speed” which does not let me drive over 20 MPH, and creates some serious shaking. It is extremely frustrating and not to mention dangerous. I have noticed that the days I put gas after driving it for about 5-10 minutes the check engine light will appear. I won’t drive it for a few days then it works fine. I need help! I have paid so much money to the dealership and they have not found out what is wrong with it. Does any one have any suggestions?
Hi Kalene. I had the same problem with my Colorado and took it to many mechanics who always seem to find an expensive solution to my problem while contradicting the other mechanics. That is until I took it to this one guy who plugged in a machine to my truck and saw that it did need some minor repairs including the Map sensor. After he unplugged the map sensor my truck stopped shaking and turning off on top of having that scary reduced power light come on. After he told me that the part cost anywhere between $30-$80 at an auto parts store he told me to try online because it can go as cheap as $6. I found a good one for $10 and even though it was something anyone can replace on their own i took it back to that mechanic to do it for me and when I asked him what I owed him he said don’t worry about it that its on him I decided to give him a $50 tip for being honest and not trying to rip me off like everyone else did. Needless to say he has a customer for life. Anyway, try the map sensor. I bet that’s what it is and its an easy fix. Good luck!
do the error codes stay in the computer or do they disappear when the light go’s out?
The codes stay in memory, even after the repair is done. You can either disconnect the battery for a few minute, or use a scan tool to clear them.
How can i fix the reduce engine power on a gmc envoy xuv slt 2004
How can I fix reduced engine power and engine light on 2008 Buick lacrosse. Dealer has no clue. They contacted general motors. And still no luck.
2017 Sierra 1 month old has this issue already! Sure my warranty will cover it but who wants a brand new truck with problems
I have a serious problem .. I over fuled my car so I had to change my engine the person who changed my engine for what ever reason did not change the airloom cable it said ‘ engine power is reduced ‘ and I was not able to drive over 30 mph .. Now the air loom cable is swapped over and codes have been rested and the new people I have taken it to have said their not sure why it’s still there . The car is driving 70-80 mph now so very strange anyone have any ideas ? I have a Vauxhall corsa 1.2 15 plate .
Have you taken the throttle body apart for any reason?? When putting in the t.p.s. throttle position sensor in, it has to be put in just right or basically u lite the fuse when turning on car.. vvvvvvvrrrrooooooooooooooommm! Or maybe just put shit back to where they came from?? And then do the reset….. that way everything is working the way it’s supposed to whend it starts fresh. ;) sounds to me your doing it all wrong boy.
I have an 08 chevy Silverado 2500 hd 4×4. last night I was driving it amd all of a sudden it said engine power reduced and wouldn’t go get fast if i tried to push the gas down to far my rpms would go up to 5 can anyone give me a few ideas on what it could be
took my 2008 silverado to chevy dealer with 104000 mles on it . the dealer said G M had a recall on the T B I and it was fixed at no cost to me. They also gave me a car to drive while mine was being repaired.
I have a 2004 Chevy Silverado 4.3 1500 when I’m going up a steep hill my check engine light flashes 2 times and I tend to lose horsepower I replace a Cadillac converter already twice and my transmission is rebuilt what could be the problem
i had the same problem my reduced engine power comes on so i couldnt do more than 15 miles per hour i pull over turn car off for 5 minutes turn back on no problem it would run until happen again it was my TPS i changed it 70 dollar part took 5 minutes no problem since then
could the use of E85 cause “reduced engine power warning and check engine light?
I had no more problems
Have you had any more problems?
Had very similar issues with my 2008 gmc savana 1500 like everyone else. I’ve spent hundreds if not thousands on repair at various autoshops in which I was slowly loosing faith in GMC/ GM. My issue was resolved with my engine power reduced problem and turns out, the vehicle iddle just needed readjusting. Not sure if that will be everyone’s fix, but it’s worth looking into. Really hope it helps.
I have a 2003 4×4 LT Chevy Tahoe with over 240k miles. Over the passed 3 years, I’d had an issue with the Reduced Power Mode coming on, shutting down my Tahoe and forcing me to pull over, turn it off, wait and the fire it back up. Sometimes it will kick it out of the Power Reduced Mode, but the engine light will stay on. Other times it won’t work, I’ll have to turn it off and wait longer. I’ve replaced the following
All seemed to work but after a while, the same issue came back. I’ve read multible forums looking for the answer, no shop has helped, no 1 forum has helped. Has anyone replaced all the here parts and still had the issue? Has anyone found the caused and fix of this issue? Truck still runs great as long as the Reduced Power Mode doesn’t come on. Please help!
I read Ken’s response to the daytime vs nighttime issue. My truck throws into the Reduced Power Mode day and night, freeway or town traffic, while driving or at a stoplight, while driving or right when I turn it in. There is no rym or reason as to the time of day or volts being pulled from the battery. Ie, lights, stereo, etc.
did you read where there was a recall on Chevrolet and problem could be repaired for free? See Wendell 1 year 11 months ago. JS maybe something there. Good luck!
Have you bought a new battery
I have. I’ve purchased 2 batteries since this problem arose.
Have you tryed replacing the camshaft sensor
I have not! Nor have I replaced the knock sensor. I was told I should have when I replaced the intake manifold. (Had I been given the option from the shop at that time, I would have.) have you seen this problem corrected by replacing the camshaft sensor? Cost and can it be done by me, or is it a shop recommended item?
Hi Dean! I have a 2004 4×4 Z71 Tahoe with right at 175k miles and am having the exact same issue with no rhyme nor reason apparently bc I can’t seem to find any consistencies for when this occurs either?! We’ve taken it to get looked at once so far where they ran diagnostics and drove it a little bit, and said it was perfectly fine. After finding this article and reading all you have replaced and have been through with this issue, I can only imagine how frustrated you must be! Just so happens I talked about wanting to sell a week prior to this issue starting, and it’s happened now about 10times within the last 3 weeks! But today was actually the first time I had to actually leave it and get someone to come pick me up. It started up just fine, but as soon as I would go into reverse to back out it would say ‘Reducing engine power’…and you know the rest! I tried several times and then waited a good 30mins before I tried again when my dad came to pick me up and/or try to drive it himself to see what has been going on. Did the exact same thing immediately, so I’m at least glad he got to finally see what is going on. Im also grateful I read this so that we now know that replacing the parts you listed above aren’t fixing or helping the issue! Any updates on figuring out what the problem is? Hope you get it figured out!
i real don’t think knock sensor will help. or the cam or crank sensor. there is a problem in the . the foot pedal or the throttle body . if its the cam or crank sensor it will kill the motor. the knock sensor will just turn on the check engine light on. and replacing the battery? it’s main job is to store power to start the motor. just have your local auto store check the batter if its good. your good. !!
now the throttle body and the foot pedal. they are both electronic sensor with sensors tell sensore to do there job . of one of the those electronic sensors get a bad connection ” Check Engine” light.. now let see if someone is will to help us out on how to check out those things thing. “electronically controlled throttles” ” foot pedal or throttle body”
2003 gmc 2500 hd, 6.0 auto 4×4. Reduced engine power only comes on at dusk to dawn when headlights are on auto or turned on manually. I pulled the two relays for high and low beam lights and it runs fine with no reduced power message. It will also happen(reduced power) when air conditioner is turned on. Seems to this old school mechanic that I have maybe several bad grounds, any thoughts? I can drive all day long without air turned on and headlight relays in place with headlights in auto mode, but not on, but when sun goes down and lights come on it goes to reduced engine power. Also both the drivers side high and low beam headlights are dimmer than passenger side, also maybe bad ground. Help!!
I have the exact same issue ken. Like identical on my 04. If you find anything out plz email me your solution.
Same exact problem. Going crazy tracing wires!! Did you find a fix?
Never found one. Pulled my relays for ac and headlights. Wired my heaflights to a switch… what a pain.. prolly.something.simple
gat a 2008 dodge magnum running 60 mph and let off gas my car jerks and the check engine light is on what is the problem
I hAve a 2014 gmc Sierra and da reduced engine power and check engine light are on what should I do
I have a 2015 Equinox & the check engine light & reduced engine capacity message came up….I am soo upset! Going to a mechanic today….
I have a 2008 Suzuki xl7. We replace the throttle body but the idle is not right. Also got the map sensor but was given a different part. What else can I do
have a 2000 Tahoe reduce engine power, traction assist, service engine soon lights come on obd2 code 1221,how do I resolve problem ?