Reduced Engine Power: What It Is and What to Do When You See the Warning Light

Last Updated: January 27, 2026 Fact Checked

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This article was co-authored by Duston Maynes and by wikiHow staff writer, Christopher M. Osborne, PhD. Duston Maynes is an Automotive Repair Specialist at RepairSmith. Duston specializes in leading a team that handles a variety of automotive repairs including replacing spark plugs, front and rear brake pads, fuel pumps, car batteries, alternators, timing belts, and starter motors. Duston holds an Associate’s degree in Automotive/Diesel Technology from The Universal Technical Institute of Arizona and is a Certified Diagnostic Technician and Automobile Mechanics Technician through BMW STEP. RepairSmith received The 2020 Big Innovation Award by Business Intelligence Group and The Startup of the Year by the American Business Awards. RepairSmith was also included in Built in LA’s 50 Startups to Watch and The Business Intelligence Group’s 52 Names Leading the Way in Customer Service. RepairSmith offers in-home services to provide car owners convenient and complete auto repair everywhere. This article has been fact-checked, ensuring the accuracy of any cited facts and confirming the authority of its sources. This article has been viewed 181,819 times.

It’s hard to ignore the “reduced engine power” warning on your dashboard—because when it lights up, you’ll also feel a clear reduction in your vehicle’s acceleration and performance. If the cause is just a signal error, restarting your vehicle may solve the problem. Otherwise, it’s important to figure out the underlying issue and get it fixed ASAP. Keep reading for helpful info on what reduced engine power is, what can cause it, and how to deal with it.

Things You Should Know

• Shut off the engine, wait 10 seconds, then restart the vehicle to see if this resets the reduced engine power light—but this will only work if it’s a signal error.
• Avoid driving your vehicle when the reduced engine power light is on—instead, identify and repair the underlying problem that’s causing the warning light.
• Have a professional mechanic diagnose and repair the problem—only attempt repairs yourself if you’re fully confident in your auto repair skills and knowledge.[1] X Expert Source Duston MaynesAutomotive Repair Specialist Expert Interview

Steps

1. 1 Shut off and restart the vehicle to reboot the electronic system. Modern vehicles are basically computers with wheels, so try the same technique you use for your phone or laptop—reboot it and hope that works! If the problem is a signal error and not an actual fault in the system, shutting off the vehicle for 10 seconds and restarting it may clear the issue.[2] X Research source
   • If the light doesn’t come back on and your vehicle drives as normal, everything is probably fine. But it’s a good idea to get your vehicle checked out by a mechanic sooner rather than later.
2. 2 Take the vehicle in for repairs ASAP if the light comes back on. If the reduced engine power light returns immediately or shortly after you restart the vehicle, it’s not just a signal error—instead, you have a genuine issue that needs immediate attention. And this is rarely a DIY-friendly issue for the average vehicle owner. Your best bet is to have the vehicle checked and repaired by a trained professional.[3] X Research source
   • Don’t bother trying to restart the vehicle again if the light comes back on after the first try. That’s your sign that there’s a bigger problem at hand.
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1. You may be able to drive slowly, but only do so if absolutely necessary. Your vehicle will only operate at low speed and with minimal performance in reduced engine power mode, which makes attempting to drive dangerous in and of itself. Additionally, driving the vehicle risks causing extensive (and expensive) damage to the engine and/or electrical system—reduced engine power mode is definitely not complete protection against this.
   • If you’re at home or parked in a safe place when this problem arises, call to have your vehicle towed to a garage. Don’t try to drive it there yourself.
   • Drive only as far as you must to get to a safe location—driving to a nearby parking lot instead of stopping on the side of a busy road, for example. Then get a tow.

1. Reduced engine power is a “safe mode” meant to protect your engine. The reduced engine power light comes on when your vehicle’s computer system senses an error or problem that could lead to significant engine damage. The system attempts to protect the engine by going into a low power mode. In addition to the dashboard light—usually a text warning like “low engine power” or the “check engine” symbol with an down-pointing arrow beneath it—you’ll notice impacts like the following:[4] X Research source
   • Your vehicle may throttle down significantly, making it impossible for you to drive at anything beyond a very slow speed. (This is why you’ll hear this referred to as “limp mode.”)
   • Instead of just slowing down, your engine may in fact shut down completely. If you’re on the road when this happens, you have no choice but to coast to the side of the road and turn off the vehicle.
   • Non-essential electrical systems in your vehicle, like the audio system, interior lights, and so on, will almost certainly shut down as a power-saving measure.
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1. Reduced engine power can be caused by a long list of issues. This isn’t a very satisfying answer, but it’s the honest one! Some causes are more common than others, especially with particular vehicle makes/models, but the list of possibilities is practically endless. Here are some of the most common causes:
   • Problems with the throttle actuator control (TAC) system, including bad circuitry, faulty sensors, or mechanical issues.
   • Failures in the clutch system, faulty oxygen sensors, or loose engine cables, wires, or hoses.[5] X Research source
   • Damage to the accelerator pedal, which contains sensors.

1. 1 Check the vehicle’s wires, cables, and belts if you have the know-how. Something as basic (but vital) as a frayed wire or a loose belt can cause a reduced engine power signal. If you have moderate or greater vehicle repair skills, go ahead and check all the wires, cables, hoses, belts, and other connectors for damage or disconnections. If you’re a typical DIYer, however, play it safe and have a professional mechanic do the diagnosis and any repairs.[6] X Research source
   • Check the fuses at the fuse panel as well. With your owner’s manual as your guide, identifying and replacing a bad fuse is manageable for the average DIYer.
2. 2 Use an OBD-II reader to identify the likely problem. Buy or borrow an OBD-II reader, connect it to the designated port (according to your owner’s manual), and use the reader (according to its instructions) to get a diagnostic code from your vehicle’s computer. Search the internet for the given diagnostic code to learn about the problem.[7] X Expert Source Ed BeeryAutomotive Specialist Expert Interview
   • If the reader displays code P2135, for example, search online for “DTC P2135” or head to a website that offers a searchable list of DTCs (diagnostic trouble codes) for OBD-II readers.
     • Code P2135 refers to mismatched readings between two throttle position sensors, which is one of the more common triggers for a reduced engine power light.
   • Even if you have no intention of attempting the repair yourself, using a OBD-II reader is an easy way to figure out the likely problem before taking your car to a repair garage.
3. 3 Take the vehicle to a pro for repairs (unless you have advanced skills). Be honest with yourself about your vehicle repair capabilities here! It’s easy to cause even more damage, leading to an even larger repair bill, if you’re not sure what you’re doing under the hood.
   • For example, if you do get code P2135, the repair may be a 30+ step process that’s beyond the capabilities of all but truly seasoned DIYers.[8] X Research source
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Community Q&A

• Question My car has been showing a reduced engine power light for five years, yet it remains drivable for daily use. What could be causing this persistent issue? Delmo Car care Community Answer If your car has been showing a reduced power warning for years but remains drivable, this often suggests an intermittent issue or that the system is operating in a 'safe mode' to protect the engine. Such warnings should always be addressed, even if the car seems to function normally. Potential causes for this condition include throttle body or accelerator pedal sensor issues, mass air flow (MAF) sensor problems, a weak fuel pump, clogged fuel filter, failing oxygen sensors, wiring faults, or an engine control unit (ECU) error. For detailed diagnostic steps, you should consult a comprehensive automotive repair guide. Thanks! We're glad this was helpful. Thank you for your feedback. If wikiHow has helped you, please consider a small contribution to support us in helping more readers like you. We’re committed to providing the world with free how-to resources, and even $1 helps us in our mission. Support wikiHow Yes No Not Helpful 0 Helpful 0
• Question Can I continue operating a TLB after an engine derate warning? Delmo Car care Community Answer You can continue operating a TLB after an engine derate warning, but it is not recommended. An engine derate means the engine is protecting itself from a serious problem, such as overheating, low oil pressure, fuel issues, or an emissions fault. While you may be able to move the machine slowly to a safe location, using it for digging or heavy work can cause major engine damage. Thanks! We're glad this was helpful. Thank you for your feedback. If wikiHow has helped you, please consider a small contribution to support us in helping more readers like you. We’re committed to providing the world with free how-to resources, and even $1 helps us in our mission. Support wikiHow Yes No Not Helpful 0 Helpful 1

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Expert Interview

Thanks for reading our article! If you’d like to learn more about engine lights, check out our in-depth interview with Duston Maynes.

References

1. ↑ Duston Maynes. Automotive Repair Specialist. Expert Interview
2. ↑ https://dashboardsymbols.com/2010/11/reduced-engine-power-light/
3. ↑ https://dashboardsymbols.com/2010/11/reduced-engine-power-light/
4. ↑ https://vehiclefreak.com/how-to-bypass-reduced-engine-power/
5. ↑ https://vehiclefreak.com/how-to-bypass-reduced-engine-power/
6. ↑ https://vehiclefreak.com/how-to-bypass-reduced-engine-power/
7. ↑ Ed Beery. Automotive Specialist. Expert Interview
8. ↑ https://www.brakeandfrontend.com/tech-tip-reduced-engine-power-message-displayed-on-gm-vehicles/

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