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Why Does Engine Power Get Reduced

Why Does Engine Power Get Reduced?

If you own a vehicle, you might know why the engine power gets reduced. But if you have recently bought a vehicle like a car and an engine’s power is reduced, you indeed think what does it mean when engine power is reduced? For your information, when you notice the Engine Power Reduced warning sign, it means the performance of your car has been limited. The primary computer of your vehicle, known as the powertrain control module, triggers the Reduced Power Mode when it notices a system failure. The “Engine Power Reduced” warning light is present on your vehicle’s dash.

This guide provides you with detailed information about why the engine power is reduced and what it means. Different ways can be used to fix this problem where you need to read this article to learn about these ways. When you notice the Engine Power Reduced sign, you need to check the engine and the fuel connection because it represents a flaw in the performance of your vehicle. This sign also shows that your vehicle has entered into a fail-safe mode.

Importance of Engine Power

Before knowing what it means when engine power is reduced, it is needed first to clear the concept of engine power and its importance for a vehicle. You should know that engine power is considered the power that an engine can put out. The engine power can also be defined as the horsepower of a vehicle.

The higher the horsepower, the stronger and the faster the speed. The right engine power of a vehicle is between 200 and 300 horsepower. If the vehicle’s engine has strong horsepower, it will have better acceleration which is considered one of the most substantial factors of a vehicle.

“Reduced Engine Power” Sign

When the performance of your vehicle is affected, you notice a sign on your dashboard, i.e., a red light that shows the performance of your car has been intentionally limited. The primary computer of your car, known as PCM, results in entering your vehicle in Reduced Power Mode whenever it detects or finds out a system failure.

This sign may appear due to different reasons where the red light may get turned on when the PCM detects a noticeable reduction in the performance of the vehicle due to an underlying concern. If you have the owner’s manual to the GM vehicle handy, you are allowed to flip to the section about the driver information center. You will get appropriate and precise information about the “Engine Power Reduced” sign depending upon the model of your vehicle.

“Reduced Engine Power” Mode

In the “Reduced Engine Power” Mode, the ability of your vehicle to accelerate is inhibited. Even if the power is not reduced immediately, the performance of the vehicle may be limited the next time you drive your vehicle. The PCM may also cut off fuel delivery to the engine, making the vehicle unable to drive. Whenever this situation occurs, the Engine Power Mode is implemented as a fail-safe mode which is also known as a limp mode.

Why Does Engine Power Get Reduced?

The primary reason behind this happening is that there is inadequate fuel pressure and volume due to different issues like restricted fuel filters or faulty fuel pumps. Sensor issues can also affect the performance of a vehicle as they can create an improper fuel/air ratio. Some other reasons behind the reduction of engine power of a vehicle are:

  • Internal engine issues
  • The problem is the variable valve timing
  • Problem with supercharger or turbocharger
  • Ignition system problems
  • Excessive back pressure caused by restricted exhaust converter
  • Vehicle stuck in “reduced power mode” or “limp mode” due to an underlying problem.

Reasons Why “Reduced Engine Power” Message is Displayed

When you ask what does it mean when engine power is reduced, it means you want to know the reasons why the engine’s red light is on. There are multiple reasons behind this happening. Moreover, GM has changed its “fail-safe” strategies; that’s why this message depends upon the year and model of the vehicle you have. Following are some of the reasons why the “Reduced Engine Power” message is displayed:

Throttle Body Problems

One of the major reasons behind the appearance of the “Reduced Engine Power” message is the problem with the throttle body or TAC system. Modern vehicles are enriched with this layout in place of a mechanical and traditional throttle body and linkage. When the throttle body becomes dirty, or it fails, you will notice that the “Reduced Engine Power” mode is activated.

In the TAC system, there are two accelerator pedal position sensors whose purpose is to determine the desire of the driver for acceleration. The throttle response is calculated by the device from a pair of throttle position sensors. Once the module has the required information from the sensors, an actuator motor is used by PCM for operating the throttle to control the airflow into the engine.

Circuit Issues

The circuit issues can also result in reducing the engine power. You should know that the TAC system consists of a pair of TP sensors. When one or both of the sensors are damaged or go bad, your vehicle will enter the “Reduced Engine Power” mode.

Bad Pedal Position Sensor

The engine power of your vehicle reduces when there is an issue with the TAC system. For example, a problem may occur when both the APP sensors stop working. These sensors are usually integrated into the accelerator pedal.

Data Network Problems

Modern vehicles consist of multiple computers that are used for communicating with one another over a data network. If this network is interrupted or there are issues with the PCM, your vehicle’s engine power can get reduced, and it may enter into “Reduced Engine Power” mode.

Problems with Cooling System

The engine power can get reduced if there are cooling system issues with your vehicle. The engine of your vehicle begins to overheat if there are cooling system issues. The PCM detects and triggers the mode for protecting the engine from further damage.

Engine Performance Issues

If there is a high-pressure fuel pump, it may result in reducing the engine power. As a result, you notice the warning sign that shows you need to resolve this issue immediately; otherwise, your vehicle will be damaged badly.

Things to Check for this Purpose

There are different things you need to check when you notice the engine power is reduced and the warning sign is being displayed. Some of these things have been mentioned below:

1. Diagnostic Trouble Codes

The first thing that is needed to check for this concern is the Diagnostic Trouble Codes. It can also be used as a scan tool for downloading the trouble codes that are usually stored in the ECM of your car or any other vehicle. Mostly, these codes will steer you in the right direction to determine and find out where the actual faults are.

2. Faulty Ground Connections

The most common thing to check when the engine power gets reduced is faulty ground connections. This might be the most common reason behind this issue because the wires and parts of the vehicle can get damaged easily. So, you need to check the condition of the engine grounds, which also includes the battery connections.

You should know that a faulty ground connection can result in causing current and voltage to drop. It also leads to different types of driveability issues. So, it is necessary for you to check the engine grounds in your car with the help of a digital multimeter. It will be helpful for you to detect damaged, corroded, and loose connections that can be affecting system circuits, actuators, and sensors.

3. TSBs and Software Updates

If you notice the engine power of your vehicle is reduced, you need to use the technical service bulletins. Most people move towards the repair process without finding a need to read all the appropriate and useful service information. You should know that a Technical Service Bulletin provides you with detailed and useful information regarding potential vehicle-related issues.

For your information, a TSB acts as a way of communication for updating automaker publications. It is helpful in describing the updates regarding different parts of your vehicle. It also informs you about potential defects and failures. You will also get detailed information about new and enhanced service procedures.

What to do when reduced Engine Power Light is turned on?

If you are driving on the road and you notice a red light present on your dashboard is turned on, you should move your vehicle back to your home or a nearby shop. And if these lights get turned on when you are at home, you should not drive your car until the issue behind this warning is resolved.

When this light comes on, the first task you need to perform is to get your vehicle scanned using the OBD scan tool. You can also use another reliable and useful scanning tool that is better than OBD. We know that different vehicles have computer modules installed in them, and errors may occur in them. You may find error codes and some other faults that can occur within the system of your truck, car, or any other vehicle.

If we talk about older vehicles, they do not have computer systems installed in them. The technology was enhanced in the 1990s when the scanning of a vehicle was introduced, but it did not produce accurate and reliable results. Plus, it was expensive too to get your vehicle scanned at that time.

In 1996, it was considered mandatory by the EPA that every vehicle must have OBD II compatible software instead of manufacturer-specific or expensive scan tools. OBD II has usually standardized all the information stored by your vehicle.

How to Fix When the Warning Light Comes on?

There are different reasons why the warning light on your dashboard comes on. The solution for all these problems is different as they depend upon the actual problem. Following are some of the solutions for different problems that result in reducing the engine’s power:

  •  Fixing Loose Wire

As we know, the vehicles are full of connectors and wires that power everything and let the car run. A short in the electrical system of your car can result in damaging the engine of your vehicle, and you may also lose ground wire or a clamp. No doubt, this issue is very easy to detect. To solve this issue, it is necessary to disconnect the battery first.

You need to check whether all the connections are in place or not. You should also check the loose wires or grounds that may have become unhooked. You also need to check the damaged or exposed wiring. You need to reconnect anything that is loose. You also need to replace the damaged or exposed wiring.

  • Fix Oxygen Sensors

The oxygen sensors can get damaged or start failing if there is a great amount of oxygen present in your vehicle through the exhaust system. They play a vital role in the adjustment of the air-fuel mixture immediately for proper combustion. If any of them is faulty, the power of your vehicle’s engine gets reduced.

This issue can be fixed by cleaning the oxygen sensor present in your vehicle, such as a car, bus, truck, etc. It means you do not need to replace it. You should know that modern vehicles consist of at least two oxygen sensors. One of them is present after the catalytic converter, and the other is present before the catalytic converter. You can use an OBD II scan to detect which sensor is faulty.

As we know, the replacement of oxygen sensors is very costly as the price of one sensor is about 500 dollars. Plus, only an expert can replace these sensors using special tools. It requires a special wrench which is not available to every single person.

  • Fix Throttle Position Sensor

As we know, the throttle position sensor is located within the throttle body near the butterfly valve. It usually opens up to allow the air to get into the engine. The purpose of this sensor is to measure the position of the accelerator pedal when you step on the gas. When it gets damaged or stops working, it results in reducing the engine power of your vehicle.

Fixing this sensor might be similar to fixing the oxygen sensor, but it is more inexpensive than fixing the oxygen sensors. The cost of a throttle position sensor ranges from 100 dollars to 500 dollars depending upon the model and manufacturer of your car. You can hire a mechanic to replace this sensor or perform this task yourself.

  • Fixing Mass Airflow Sensor

For your information, a mass airflow sensor is present between the intake manifold and the air filter. When it gets damaged, it results in affecting the engine power of your vehicle. To fix this issue, first, you need to clean this sensor to make it free from any kind of dust and debris. You can also use a cleaning spray for cleaning the dust stuck in the air filters.

You can also replace this sensor, but you must also be aware of the replacement cost, which is about a hundred dollars. Performing this task is not so difficult as you can perform this task yourself without the need for any mechanic.

  • Fixing the Catalytic Converter

As we know, the catalytic converter is present underneath your car, truck, or any other vehicle after the exhaust manifold. The purpose of this converter is to convert the carbon monoxide into carbon dioxide through oxidation and reduction. This converter can become clogged, which in turn results in reducing the engine power of your vehicle.

You can fix this issue by replacing the catalytic converter. No doubt, it is expensive to replace it with a new one because of the material used for its manufacturing. Plus, it will also cost you more than 2000 dollars. So, you can also replace it yourself. All you need is a jack stand and some other necessary tools you need to get underneath your vehicle.


Why does engine power get reduced?

The major issue behind this happening is inadequate fuel pressure and volume due to different issues like a restricted fuel filter.

When would I know the engine power is reduced?

You will notice the red light present on your vehicle’s dashboard is turned on, which represents that your engine power is reduced.

How to fix this issue?

You can fix this issue depending upon the cause behind it, such as you need to tighten the wires or replace the damaged wires, fix the failed sensors, etc.


There are different reasons why your vehicle’s engine power has been reduced. Some of these reasons include the issue of sensors, wires, vehicle parts, engines, etc. You need to review everything and make sure you do not drive the vehicle until the issue is resolved. You can either call a mechanic or solve such an issue yourself if you have some indication about it. You must also be aware it might be costly to repair or replace some of its items.

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