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Home / Symptoms / Reduced Engine Power Light

Hey, Why Is My Car's Reduced Engine Power Message On?

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Four common causes for a reduced engine power warning on the vehicle and their related parts.
Your vehicle’s engine is controlled by the powertrain computer to produce the appropriate amount of power that is required to perform properly. If for some reason there is a condition that is related to safety or will drastically increase the amount of costly damage that may happen to the vehicle. The vehicle's powertrain computer will instigate a power reduction protocol that will limit the amount of speed and acceleration at any given time that malfunction is happening.

Are You Experiencing a Reduction in Your Car's Engine Power?

The reduced engine power light appears because the vehicle has limited its power output based on a problem it has detected; this is a designed safety measure. This is caused by issues with the fuel pump or catalytic converter. Alternatively, faulty sensors might be triggering this.

Spot the early warning signs of reduced engine power and take action before symptoms worsen. We recommend you communicate any concerns to a technician for professional assistance.

Our guide will teach you how to watch for any warning signs of engine power issues. Trust us; it's better to catch these things early on before they become big problems. Not only will it save you time and money, but it'll also give you peace of mind on the road.

Let's Get To The Bottom Of It!

Has your vehicle's power worsened?

The fuel pump is an electric device inside the gasoline tank that pumps a specific amount of fuel to the engine. However, if it stops working properly, the engine may not receive enough fuel, resulting in a loss of power.

In addition you may notice the check engine light on the dashboard, fuel economy decrease, engine underperformance, or engine stumbling.

Is the vehicle unresponsive when you press the accelerator pedal?

The engine control module connects your car's gas pedal and throttle body. The pedal has sensors telling the computer how fast and swiftly the driver presses the pedal. The computer then uses this information to open or close the throttle body's plate. There are also sensors in the throttle body that measure the throttle plate's position. If these sensors or the wiring fails, the computer activates the check engine light and limits the car's performance for safety. This makes the vehicle feel unresponsive when you press the gas pedal.

If you notice the vehicle idling high, cranking and not starting, the engine stuttering, or underperforming, save this information; they're essential if you go to an auto shop later.

Is your check engine light on?

The ECM (Engine Control Module) is the brain of the engine and powertrain. It controls the engine's air and fuel flow and cylinder firing time. The ECM uses input from sensors on the vehicle to make these decisions. If the ECM receives correct inputs but doesn't send the right outputs, the check engine light activates, and the car may underperform. For example, if a coil driver, which sends signals to the coils, fails, it causes a cylinder misfire, activating the check engine light.

If you notice the vehicle shuddering, losing extra fuel, limited to certain speeds, the engine stuttering, or underperforming, save this information; they're essential if you go to an auto shop later.

Is your vehicle taking longer to accelerate?

The catalytic converter is a part of the exhaust system that helps reduce emissions. It has precious metals that help reduce pollutants when the engine runs correctly. However, the catalytic converter can clog and overheat if the engine is not running correctly, like getting low oxygen or too much fuel. This can restrict the exhaust flow, leading to power and acceleration loss. The vehicle may also feel sluggish.

If you notice the engine stalling, long cranking time, poor power when merging on a highway, low fuel mileage, or the check engine warning light on the dashboard, save this information; they're essential if you consider going to an auto shop later.

Is your car idling high?

The throttle body is a part of your car's engine that controls the amount of air that goes in. The car's computer controls it, but there's also a part that helps to set a proper idle speed. If either this part or the throttle body gets clogged with gunk, your car underperforms, sometimes making the idle too high.

If the throttle plate position is wrong, the engine control computer sets a fixed limp mode, triggering a reduced engine power warning light.

It is important to take note of any symptoms like a high engine idling, long cranking time, shuddering, the need to hold the throttle open to start the vehicle, speed limitations, or a decrease in fuel mileage. This information will be useful if you visit an auto shop later.

Is your vehicle hesitating under hard acceleration?

The mass air flow sensor sits in the intake before the throttle body. It measures the amount of air coming into the engine, helping the car's computer calculate how much fuel and engine load gets good performance. However, if this part gets dirty, it can give false readings, causing the car to hesitate when accelerating or not accelerate at all.

It is important to take note of any symptoms such as engine stalling and not starting, cranking for an extended period, the vehicle shutting off, speed limitations, poor performance, or a decrease in fuel mileage. This information will be useful if you visit an auto shop later.

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Vehicle Health Inspection Proof

Explore the following typical inspection results that show a potential cause for the symptom and select the one you believe is similar to your vehicle's issue.

Throttle pedal sensor malfunction

This image shows a throttle pedal assembly. The red arrow points to the throttle pedal sensor's location. In this case, the sensor had a glitch and required replacement.

The customer dropped off their vehicle because it was moving oddly. The engine was also idling very fast, and when they put the car in gear, the engine almost died. They had to press the gas pedal lightly and could only drive 35 mph.

During a test drive, the technician saw the check engine light active on the dashboard, and the car wasn't responding to the gas pedal. Instead, it was in a mode that limited its power as a safety measure.

They did a scan during the vehicle health inspection, finding a problem with the sensors that measure the gas pedal's position. To further assess the issue, the customer approved additional tests.

During additional tests, the technician found that one of the sensors on the gas pedal had a glitch and was bottoming out halfway through the sweep. As a result, the whole gas pedal assembly needs to be replaced.

Throttle body issues

The proof image shows a dirty throttle body blocking airflow and causing the vehicle's idle to be high. In this case, the body needs cleaning or replacement.

The customer dropped off their vehicle because it was hard to start and had a high idle. They also noticed that the check engine light was active on the dashboard.

On the test drive, the technician observed that the vehicle had a very high idle, around 1100 RPMs, and the check engine light was on.

The technician noticed the throttle body was dirty during the vehicle's health inspection. To further investigate the issue, the customer approved additional tests.

The technician used a special scanner during additional tests to check the idle. They found it too high and unadjustable due to dirt. They recommended cleaning the throttle body and the upper intake. The customer agreed, and after cleaning, the technician adjusted the idle, and the vehicle worked normally.

Faulty engine control module

The image shows the location of a wire on the engine control unit (ECM) that was checked to confirm that the component controlling coil one had failed. In this case, the ECM needed replacement.

The customer reported that their car was jerking and shaking, and the check engine light came on and sometimes flashed. They also saw a message saying the engine was in power reduction mode.

When doing a test drive, the technician saw that the check engine light was on and the car was having trouble accelerating.

During a vehicle health inspection, the technician found some diagnostic trouble codes and did further testing. They found problems with the ignition coils, and one of the cylinders wasn't firing correctly. To further address these issues, the customer approved additional tests.

The technician tried switching out coils during additional tests, but the problem stayed on the same cylinder. So they checked the wiring and found the issue was with the engine control module (ECM). To fix the problem, the ECM needs replacement.

Weak fuel pump

This proof image shows a mechanical fuel gauge. In this case, the gauge indicates that the vehicle has low fuel pressure.

A customer brought their vehicle to the shop, reporting it felt weaker to move. The vehicle seemed hesitant, and the customer thought it might need a tune-up.

During a test drive, the technician noticed that the check engine light was on, and the vehicle was slightly sluggish and hesitant when accelerating.

The technician did a vehicle health inspection and ran a diagnostic code scan. They found a code that indicates "system too lean" on bank 1. However, no other issues were found related to the customer's concern. So, the customer approved additional tests.

During additional tests, the technician used a specific scanner, discovering that the bank one fuel trim was not lean at idle. So, the computer tried adding fuel while the vehicle was running. This indicates a malfunctioning fuel pump.

The technician tested the fuel pressure using a mechanical pressure gauge, discovering it was well below the specified level. Plus, it had a blocked return line, which indicated a failing fuel pump. The technician recommended replacing the in-tank fuel pump and retesting the vehicle.

Clogged catalytic converter triggering the "check engine" or "reduced engine power" light, making the car lose performance

This image shows a clogged catalytic converter's interior. In this case, it's restricting airflow and needs replacement.

A customer brought their car to the shop because it was having trouble accelerating, and the check engine light was active on its dashboard. They also mentioned that the car's fuel efficiency was decreasing.

When the technician took the car for a test drive, they noticed that the check engine light was on and there was poor acceleration.

The technician found a problem with the catalytic converter during the vehicle health inspection using a code scanner. They also noticed that the primary and secondary oxygen sensors were not working correctly. To further address this issue, the customer approved additional tests.

The technician found that the catalytic converter was clogged during additional tests and needed replacement. They also suggested that other issues, such as failing spark plugs or a dirty air filter, could require analysis.

Faulty mass airflow sensor

This proof image shows a debris-affected mass airflow sensor. In this case, the debris causes acceleration issues, and the sensor needs cleaning or replacement.

The customer brought their vehicle to the shop because they noticed a lack of power and acceleration when trying to drive. They were facing a reduced engine power issue.

The technician did a test drive, confirming an issue with the car's acceleration power and the check engine light on the dashboard.

The technician found the air filter dirty and with poorly sealed housing during the vehicle health inspection. They also ran a diagnostic scan and found a code indicating a problem with the mass air flow sensor. To further investigate the issue, the customer approved additional tests.

During additional tests, the technician had someone drive the car while they monitored the sensor with a specialized scanner. They found that the sensor was sending incorrect information to the engine.

To further investigate the issue, the technician cleaned the mass air flow sensor and retested its signal. After cleaning the sensor, the technician test-drove the vehicle again, finding a positive change, but the sensor still did not reach the expected value requiring replacement.

With a new sensor, the engine now receives correct information. Finally, the technician recommended the customer an air filter replacement to protect the new sensor since cleaning alone is not the complete fix.

Typical Fixes to Address the Cause(s)

The following chapters bases themselves on experiences from our auto repair shop; we'll describe related problems' causes and fixes.

Sometimes a problem is more challenging to describe than it initially looked like. If you are not sure your problem is described by this article, please find below similar vehicle symptoms, which might describe better the issue you are experiencing.

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