Engine power reduced: Causes & troubleshooting tips

Engine power reduced: Causes & troubleshooting tips
If you've ever felt like your engine began to power down while driving happily on the road, chances are there’s something wrong with its performance. And this reduced engine power issue will no doubt be signaled as the all-too-familiar check engine light.

On some vehicles, the "reduced engine power" light on the dashboard may also light up. This shows that something is wrong with your vehicle, and the engine power is reduced.
But what causes reduced engine power? How can you address it? Let's dive in.

What does engine power is reduced mean? 

Reduced engine power can indicate more than one problem. Usually, it means that your vehicle's performance has been intentionally limited by the engine control unit (ECU). This is often a protective measure taken by the vehicle. It's done to prevent further damage when it detects a system failure or abnormal sensor readings.  

In essence, if you ever notice your car slowing down – it’s time for a check-up. 

Limp mode – a car's self-preservation mechanism  

If it so happens that your vehicle’s engine power declines, it may be a sign it’s gone into what’s known as the limp mode. The vehicle does so when it detects a serious issue that could potentially cause damage. It's a self-preservation feature that can reduce engine power, lock the transmission in a lower gear, and limit RPMs. 
You might start thinking, is driving a car with reduced engine power safe? Short answer – not really. 


While in limp mode, you'll still be able to drive. But in this case, your next destination should be your technician or the nearest workshop.  
It’s true that limp mode limits acceleration to protect car components. However, this limitation can be dangerous. You might experience difficulties while overtaking, changing lanes, or turning. 


Reduced engine power common causes   

 There are several causes, ranging from low fuel levels to more serious mechanical issues. Common causes may include:  

Throttle body issues 
A malfunctioning throttle position sensor or a dirty throttle body can lead to reduced engine power. 

Electronic throttle control (ETC) system malfunction 
Modern vehicles often use electronic throttle control systems. Any issues with the ETC system can trigger the "Reduced Engine Power" warning. 

Mass Air Flow sensor (MAF) failure 
A faulty MAF sensor can cause incorrect readings of incoming air, leading to engine power reduction. 

Accelerator pedal position sensor (APPS) failure 
The APPS is responsible for sending signals to the engine control module, and a failure can result in reduced power output. 

Engine misfire 
Misfiring cylinders due to spark plug or ignition coil problems can cause the engine to run poorly and trigger the warning light. 

Exhaust system malfunction 
A blocked or malfunctioning catalytic converter, failed oxygen sensor (also known as O2 or lambda sensor), or exhaust gas recirculation (EGR) system can lead to power loss. 

Fuel system issues 
Problems with the fuel delivery system, malfunctioning fuel pump, or faulty fuel pressure regulator can lead to insufficient fuel supply and reduced engine power. 

Engine control unit issues 
A malfunctioning engine control unit has an impact on the engine's performance. It can cause the engine to go into a limp mode, reducing power to protect it from further damage. 

Transmission problems 
Faulty transmission sensors or any issues within the transmission can cause the vehicle to go into limp mode, resulting in reduced power. 

Throttle system calibration 
In some cases, the throttle system may need recalibration or reprogramming to resolve the reduced power issue. 

Wiring and car's electrical system problems 
Faulty wiring, loose connections, or electrical issues can disrupt various engine systems and lead to power loss. 

If the engine overheats, it may cause the vehicle's computer to reduce power to prevent further damage.  


Identifying the causes of reduced engine power 

As with any issue – paying close attention to the signs will help to successfully diagnose the cause of the reduced engine power. Early detection of this problem can prevent further damage and unnecessary repair costs. 
Reduced engine power troubleshooting table 
Symptom  Possible Causes 
Reduced acceleration 
- Fuel system problems (e.g., clogged fuel injectors)
- Accelerator pedal sensor issues
- Clogged air filter
Warning light on (Check Engine Light) 
- Catalytic converter issues
- Spark plugs or ignition coil issues
Engine misfires 
- Spark plugs or ignition coil issues
- Fuel system problems
Irregular idle 
- Throttle body or accelerator pedal sensor issues
- Vacuum leaks
- Faulty idle air control valve
Sudden stalling or power loss 
- Fuel system problems (e.g., fuel injector issues)
- Electronic control module problems
- Crankshaft or camshaft sensor malfunction
Poor fuel economy 
- Oxygen sensor failure
- Fuel injector issues
- Clogged air filter
Transmission shifting issues 
- Transmission fluid level or quality
- Transmission control module problems
Decreased engine performance 
- Engine oil quality or level issues
- Catalytic converter efficiency
- Fuel system issues (e.g., fuel injector)

To identify reduced engine power issues more accurately, consider using an OBD2 code reader. This tool will provide you with detailed descriptions of diagnostic trouble codes, making it easier to find the cause of the problem. 


What happens if you ignore the reduced engine power  

Driving with an engine that’s not working at its total capacity isn't just inconvenient – it can also be dangerous. Reduced power can lead to poor acceleration, making it difficult to drive at highway speeds or navigate traffic safely.

Ignoring this warning can lead to more severe and costly damage to your vehicle's engine and other systems over time. It's always better to replace faulty components as soon as possible.

Diagnosing reduced engine power with OBDeleven  

Nobody wants to face the risks of engine power problems while driving. That's why more and more people, including professionals and daily drivers, are now turning to DIY car diagnostic techniques. 

Among the tools facilitating this shift is OBDeleven, a smart Bluetooth-enabled scanner designed for ease of use with all car models. It can help you understand what's going on when your check engine light comes on. 

You can run Advanced Diagnostics to scan, read, clear, and get detailed information about every fault code in different control units. Plus, track live data, identify critical issues, clear non-critical codes, and share these logs with technicians or dealerships. 

How to troubleshoot and fix reduced engine power  

Once you've diagnosed the issue, you can begin troubleshooting. This might involve replacing a clogged fuel filter, cleaning a dirty throttle body, replacing a dirty air filter, or addressing brand-specific issues. Remember, it's crucial to promptly address and fix reduced engine power causes to prevent further damage to your vehicle.  

Closing thoughts 

Reduced engine power is more than just an inconvenience – it's a warning sign that your vehicle needs attention. By understanding what causes engine slowdowns, you can address the issue. Doing so will ensure your vehicle stays in top shape. And it will continue to serve you reliably for years to come.