What Does The “Reduced Engine Power” Warning Light Mean?

From commuting to work to driving the kids to school, a car is part of your daily routine in numerous ways. And, it is understandable that when you experience reduced engine power, a vehicle’s sluggish response to your gas pedal is a huge concern.

Older vehicles faced challenges such as needing to replace spark plugs or wires, replacing rotors and distributor caps, and adjusting carburetors. These days, though, you will face a broad range of more modern problems that can be behind your vehicle’s issues with acceleration.

This article seeks to explain all the possibilities for reduced engine power. Read on to learn everything there is to know about why your vehicle accelerates sluggishly.

What Does ‘Engine Power Is Reduced’ Mean?

The Engine Power Reduced warning means that your vehicle’s performance is limited. The PCM detects a system failure and causes the alert message to illuminate. Depending upon the warning message, the engine may not operate normally.

The reduced power can hinder the vehicle from shifting, and it can prevent you from accelerating. In some cases, the PCM will limit fuel to the engine, and you may end up with a car that no longer runs.

Some people call this system fail-safe mode. However, it is also referred to as limp mode, where you at least have time to drive home safely without creating any damage to the engine or transmission. 

This warning message is very common feature on Chevy vehicles rather than the limp home mode in other manufacturers.

Trouble Codes that Are Related to Reduced Engine Power

Depending on the vehicle you own and the issues detected by your ECU, different trouble codes will be logged into the ECM memory. These trouble codes include:

• P0120-P0124: This indicates the malfunction of either the pedal position or throttle position device and their circuitry.
• P1125: This indicates a bad system or component fault, but it depends on the year, make, and model of the vehicle.
• P1518: Points to a bad system or defective system element fault, but the vehicle’s make and model will certainly determine this.
• P2111: This code indicates that the throttle actuator control system is stuck in the fully open position.
• P2135: This indicates the problem with the APP, TP sensor, or switch with one of the A/B voltages opening or closing.

For effective and thorough diagnosis and repairs, the vehicle has to be brought to a local service shop to be checked by a professional mechanic.

What is Fail-Safe Mode?

The message of “engine power reduced” indicates that your vehicle has developed a problem and has shifted into a fail-safe mode. Every contemporary car features a safety net that has been strategically implemented to protect drivers.

In an attempt to safeguard the individual utilizing the car or to restrain the damage that may occur to the vehicle itself, the car’s ECU might switch to fail-safe mode. It is important to note that there are multiple ways in which the onboard electronics of a car can put it into a failsafe mode, all of which differ in the capacity they allow to perform.

For instance, in the case that the electronic throttle actuator is malfunctioning, the electronic throttle control unit can adjust the maximum throttle opening to a lower level. Alternatively, in a scenario where the issue lies with the transmission system, the control unit may restrict transmission function to a specific set of gears.

Some makes and models of vehicles are designed to show specific notifications on the control panel alerting the user that the automobile is operating in a fail-safe mode. For other vehicles, an illumination of the check engine may indicate the same functionality.

Common Signs of Reduced Engine Power

On its own, the warning light indicates a greater issue. Before it even turns on, there are a few symptoms indicating the issue of the engine’s power running low. These signs may include:

• Diminished Acceleration: Your vehicle finds it difficult to accelerate, particularly when driving on expressways.
• Irregular Performance: The vehicle might behave differently with unstable idling, difficulty in maintaining steady speeds, or higher than usual noise levels.
• Decreased Fuel Efficiency: The vehicle’s performance has diminished and requires more frequent refueling.
• Check Engine Light: The check engine light can come on either before or simultaneously with the reduced engine power indication. This is a critical condition that should not be neglected.

These are only a few of the most basic signs. They are not specific to any model of vehicle, which means no matter the make of the vehicle you drive, it is essential to monitor your vehicle’s performance and any changes that may happen.

Causes of Reduced Engine Power Warning

Reduced engine power warnings are typically caused by bad engine sensors which include a bad oxygen sensor, MAF sensor, or a bad throttle body. A bad connection to one of these sensors can also cause this issue. A clogged catalytic converter is frequently to blame also.

However, reduced engine power warnings come from so many different reasons, so you should never just replace a part because you think it’s bad.

The easiest and most precise way of determining what’s causing the Reduced Engine Power Warning message is by checking the trouble codes with an OBD2 scanner. Whenever the message comes on, there is almost always a trouble code that has been stored in the system.

This will help you save a lot of money because you’ll know which parts actually need to be repaired or replaced, rather than just guessing which parts are good or bad, and maybe replacing a perfectly good part at random.

Here are some other ideas of what may cause a reduced engine power warning:

#1. Loose Connection.

All the major elements in your vehicle are connected with wires. A short in the electrical system or disconnected wire could cause the engine to go into fail-safe mode. The same applies if you have a loose clamp, or a ground wire that isn’t well-connected.

While this is often not hard to correct, it isn’t usually easy to find. You will most likely have to conduct a full inspection of the systems to locate a defect.

#2. Defective Oxygen Sensor.

Oxygen sensors measure the amount of O2 leaving the exhaust. If there is too much or not enough O2 being sent out the ECU will adjust the air-fuel mixture to calibrate performance.

But if a sensor is faulty the data sent back to the computer could potentially trigger adjustments.

This causes a lean or rich mixture, which leads to performance issues, enginer issues, and potential Reduced Engine Power Warning.

#3. Throttle Body Issues.

The throttle body consists of several parts that can go bad and cause these warnings. First, the butterfly valve controls the amount of air that gets put into the engine. If this valve falls apart, the correct amount of air cannot enter the engine.

Carbon can also be built up around this valve, causing problems with how it operates. If the engine cannot get enough air, it is going to misfire and sputter, including the warnings on the dashboard.

Not far from the butterfly valve is the throttle position sensor that needs to work properly to let air move freely. This sensor reads the position of the gas pedal and tells the computer to open the butterfly valve for the right amount of blown-in air.

If this sensor is faulty as well, the butterfly valve does not get the correct data and will constrict the air.

#4. Malfunctioning ECU.

The Engine Control Unit is the brain of the entire operation. All of the sensors communicate what is going on with the ECU, so proper adjustments can be made. If the air-fuel mixture isn’t right, the ECU alters what’s happening to better performance.

When an ECU begins to fail, it can create any number of issues. You will become unaware of poor performance while compensating for problems that may not be problems.

#5. Failing Mass Airflow Sensor.

The MAF sensor is located between the intake manifold and the engine air filter. It measures the pressure and density of incoming air to the engine.

Then, it sends the data to the ECU so the right fuel ratio can be used. If the MAF sensor fails, it sends bad data, causing problems with the ratios and causes warning lights to go on.

#6. Clogged Catalytic Converter.

After the exhaust manifold is the catalytic converter. Its job is to change hazardous exhaust gases and convert it into less harmful pollutants.

However, if the engine hasn’t been operating correctly or just due to aging, the catalytic converter can get plugged up.

The vehicle desperately needs to have the catalytic converter replaced because it will not only fail the emissions test, but you are going to have some engine performance issues. It will not always have the Reduced Engine Power Warning illuminate, but if anything, you are going to have the Check Engine Light at a minimum.

#7. Transmission Failure.

Transmission problems can cause a lot of headaches. It can slip or become low on fluid, which will spit out some codes.

People don’t realize a loss of engine power is related to a transmission issue. If you go through the list of reasons and none have been the cause, it may be time to consider the transmission.

What Causes Fail-Safe Mode?

Similar to when there is a warning for “Reduced Engine Power”, your vehicle may enter a fail-safe mode for numerous reasons. Below is a list of some possible causes:

• Automatic Transmission Troubles: Any problems with your vehicle’s transmission or the electric controls may force its transmission into fail-safe mode. This is what is often referred to as „Limp Mode”. In this case, the transmission line pressure is likely to rise, and the unit defaults to a set gear.
• A Faulty “Drive-By-Wire” System: Modern-day vehicles come with an automated system called drive-by-wire that does away with the mechanical sides of steering with complex electrical systems. Most of the time, when something goes wrong with one of these systems, the ECU has no choice but to limit the car’s performance to protect the vehicle and everyone in and around it.
• Charging System Problems: Older models have numerous electronics that rely on the power of the battery. In some cases, a weak battery can decrease their performance, resulting in the vehicle to enter a fail-safe mode. If your alternator is undercharging or overcharging, this could possibly trigger the fail-safe mode as well.
• Faulty or Damaged Wiring: Faulty or loose wiring can inhibit the proper functioning of a vehicle’s onboard electronics. This, in turn, can cause numerous issues, including the inability for the vehicle to operate; it instead goes into fail-safe mode.
• Engine Performance Troubles: Alongside other performance-related issues such as overheating and misfiring, a vehicle may enter a state of fail-safe mode; this is possible due to myriad failures of performance aspects of the engine.
• Control Failure: For controllers that should safeguard the vehicle or those inside, a fail-safe power system may be engaged to provide just the minimum level of operations necessary for fault detection.
• ECU or Data Network Problems: Modern vehicles are equipped with many data modules, also known as ECUs, that can communicate over a single data bus. If communication between them is disrupted, or one of the critical ECUs is mute, the vehicle will default into fail-safe mode.

All of the issues listed above have the potential to put the vehicle into fail-safe mode while at the same time reducing the power of the engine.

Is Driving Possible When The ‘Reduced Engine Power’ Warning Light Is On?

It is possible to continue driving your vehicle even when the ‘reduced engine power’ light is on. “Limp mode,” as it is referred to, is the maximum extent to which you should drive your vehicle, within reason.

The risk of driving in this mode is limited. However, driving the vehicle will not be a pleasurable experience because gas consumption is bound to be high, acceleration is bound to be weak, and on some vehicles, shifting may be rough.

Also, some vehicles may shut down optional supplementary features like the radio. In short, while it is possible to drive when the ‘engine power reduced’ indicator is illuminated, the vehicle should be towed if it needs to be driven more than a few miles.

Steps to Diagnosing & Fixing Reduced Engine Power

Thinking about the listed causes, the following steps should be taken to troubleshoot the issue and get on with driving:

• Stop the Vehicle: The first step after noticing a decline in the engine power while driving is to carefully pull over and stop the vehicle.
• Check Engine Light: Look for the check engine light and see if it is active or not. Flashing could indicate some more serious problems, in which case it is safer to call for roadside support.
• Restart Vehicle: First, stop the car and switch the engine off. Then wait for about 15-20 seconds before turning it back on. In some cases, these steps will reset the system and alleviate the problem.
• Check Fluid Levels: Ensure the recommended levels have not been exceeded or fallen short. In particular, insufficient engine oil or coolant can lead to further reduced engine power.
• Scan for Error Codes: An illuminated check engine light indicates the use of an on-board OBD-II scanner, which should be used to retrieve the relevant error codes.
• Inspect Throttle Body and Sensors: Ascertain that the throttle body and related components like the mass airflow sensor and oxygen sensors are free of any unclean or non-functional parts.
• Look for Exhaust Blockages: A malfunctioning exhaust system produces a powerful odor of sulfur. If you suspect a problem, have a mechanic check it.
• Seek Professional Assistance: If the diagnosis has been performed but the problems persist, don’t hesitate to take the car to your preferred automotive service shop.

With this sequence of steps, diagnosing and solving the problem independently should be straightforward! However, a competent mechanic should always be consulted as they will have the best experience and knowledge when it comes to properly diagnosing and troubleshooting the vehicle.

Make sure to not ignore problems such as reduced engine power. This could lead to further detrimental impacts for the vehicle and driving safety. Make sure you are keeping an eye out for these red flags and reacting to them on time.

Reduced Engine Power Repair Cost

The cost of a Reduced Engine Power Warning repair can range anywhere from $0 to $2,500, and the only way to know exactly where it would land is to appeal to find out what the issue is.

An engine code scanner should help narrow down where the issue lies. The OBDII scanner read all fault codes, and thus indicate what systems are possibly responsible.

Ideally, you would find that a connection is loose and if you could reconnect it, it would cost you nothing. On the other hand, you could be looking at a very costly fix, like replacing the catalytic converter or replacing the ECU right there which could result in your vehicle being junked.

You should never drive with the Reduced Engine Power Warning light on. If your vehicle is in Limp Mode, you should drive straight to a safe place and turn the vehicle off. Turn your hazard lights on to let other drivers know you are having vehicle problems.

If you have more than a few miles to drive, I would recommend towing the vehicle instead. You don’t want to get stranded on the side of the road or cause an accident when you have reduced power.

FAQs.

How do you resolve the reduced engine power warning message?

To resolve the reduced engine power warning message, you need to first scan the trouble codes and read them with an OBD scanner.

The engine power reduced warning means there are one or possibly more trouble codes stored in the ECM. At this point, it will be a lot easier to diagnosis the problem if you make sure to read the codes first.

Can you drive with reduced engine power?

No, it is not safe to drive with the engine power reduced warning. The severity or cause severity will not be understood until the problem is diagnosed properly.

The cause of the engine power reduced message could be a simple fix or something relatively serious that may cause even more damage to your engine if you continue without diagnosing and resolving the situation.

Are reduced engine power codes serious?

The seriousness of a reduce engine power reset can be serious or non-serious. It could be something simple like battery capacity, or it could be a real engine problem internally that will be aggravated and very costly if you ignore it.

Can low oil cause less engine power?

Yes. Low oil can result in a reduced engine power warning message. Low oil can lead to low oil pressure which can negatively affect the engine in many possible ways. In the worst case, it can lead to serious engine damage if you do not correct the problem in a timely manner.

Can a reduced engine power message be a battery problem?

Yes. A reduced engine power message can also be caused by a bad or low car battery. Modern cars are very sensitive to batteries, and if the car battery power is low, then it could lead to many different electrical problems with your car.

However, do not just replace the battery without diagnosing it first, because there are many potential problems that can display the reduced engine power warning message.

The reduced engine power warning message is telling you that there is a problem with your engine or transmission and there are trouble codes stored in the engine control module. There are many potential problems that can cause a reduce engine power warning message.

Therefore, it is very important to read the trouble codes with a compatible diagnostic scanner before replacing any parts in an effort to remedy the issue. Otherwise, you could waste money by simply guessing and replacing working parts.

The reduced engine power message means your engine has entered a safe mode to prevent further engine damage, and it is never wise to ignore this message.