Blog Car Care Advice Engine Power Reduced Warning Light: 9 Reasons + 4 Fixes
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Engine Power Reduced Warning Light: 9 Reasons + 4 Fixes

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Every modern vehicle has an array of dashboard lights designed to communicate potential issues or malfunctions to the driver. 

Amongst the various cautionary lights, the reduced engine power warning light signals your vehicle has underlying issues that impede its usual engine performance.

Discover everything about the reduced engine power warning light, its potential triggers, and more.

This Article Contains:

Let’s begin.

What Does the Engine Power Reduced Warning Light Mean?

The reduced engine power dashboard light indicates an issue with your vehicle’s engine or related components. When triggered by the engine control unit (ECU), the car activates “reduced engine power mode” to protect itself from potential engine damage.

But what does reduced engine power mode entail?
Reduced engine power mode limits your vehicle’s speed and acceleration. However, in some cases, reduced engine power mode cuts off fuel to your engine, making your vehicle undrivable

Now you may wonder: Is the reduced engine power light different from the service engine soon light? 

Well, yes. The reduced engine power light indicates a specific problem related to engine performance. On the other hand, the SES light is a more general warning for various engine service or repair issues.

Now that you know about the reduced engine power light, let’s explore its triggers.

9 Possible Causes of Reduced Engine Power Light

Several issues can activate the reduced engine power warning light, including:

1. Fuel System Issues

The fuel system manages the delivery of fuel to the engine. Issues with the system can result in inadequate fuel supply to the engine, leading to reduced power.

These problems generally stem from a malfunctioning fuel pump, clogged fuel filter, or a faulty fuel pressure regulator. Once detected, the engine control unit (ECU) activates the engine power reduced light. 

2. Throttle System Issues

The throttle system is responsible for controlling the engine’s power output. However, it comprises several components that could active the engine power reduced warning light, such as:

Throttle body & throttle plate: The throttle body and throttle plate assist the accelerator pedal. These parts can’t function when clogged, leading to reduced engine power.

Throttle position sensor (TP sensor): The TP sensor observes the throttle plate position and sends this information to the vehicle’s ECU. If the sensor is faulty and sends incorrect data, the ECU reduces engine power.

Throttle position sensor cover (TP sensor cover): The TP sensor cover is a protective casing that houses the throttle position sensor. If damaged, it can expose the TP sensor to dirt, causing inaccurate readings.

Electronic throttle control components: The electronic throttle control components link the throttle system together for better control. When damaged, the system fails, triggering the reduced engine power warning light.

Accelerator pedal sensor: The accelerator pedal sensor also monitors the movement of the gas pedal. A faulty sensor sends incorrect data resulting in reduced power output.

3. Failing Mass Airflow Sensor

The mass airflow sensor monitors the pressure and density of the air that enters the engine. It sends this data to the ECU, which adjusts the air-fuel ratio accordingly. When the MAF sensor is faulty, it sends the wrong data, which impacts the air-fuel ratio and triggers the reduced engine power warning light.

4. Bad Spark Plugs

A spark plug ignites the fuel mixture in the cylinders, powering the vehicle. When it malfunctions, it can lead to incomplete combustion, reduced engine performance, and triggers the engine power reduced dashboard warning light.

5. Damaged Oxygen Sensors

Oxygen sensors help the ECU adjust the air-fuel mixture for optimal performance. They may send inaccurate data to the computer when faulty, leading to reduced engine power.

6. Faulty Engine Grounds

Engine grounds are electrical connections that provide a direct path for current to flow in a vehicle, ensuring the proper functioning of electrical components. Faulty grounds can lead to electrical issues, eventually triggering the reduced engine power warning light.

7. Clogged Catalytic Converter

The catalytic converter controls emissions and burns harmful pollutants in the vehicle’s exhaust gases. When it’s clogged, the exhaust gases don’t flow freely, leading to incomplete fuel combustion. Incomplete combustion can cause an engine misfire and reduced engine power.

This issue may not always activate the reduced engine power light, but you can expect an illuminated Check Engine Light.

8. Transmission Failure

Your transmission system uses transmission fluid and several components, like the gearbox, intermediate gear, and axle, to transfer power from the engine to the wheels.

However, transmission failure due to low transmission fluid levels or a damaged intermediate gear can reduce the system’s ability to transfer power. This results in reduced engine power output.

9. Faulty Engine Control Unit

The engine control unit (ECU) manages engine functions and monitors all sensors. It may send incorrect signals when malfunctioning, causing the vehicle to enter a safe mode with limited engine power.

Knowing what can trigger the reduced engine power warning light is essential.
But what can you do to fix it?

4 Ways to Fix Reduced Engine Power

Fixing the issue of reduced engine power is complicated, so it’s best to leave it to professionals. Here’s what an auto repair mechanic would do:

1. Check for Diagnostic Trouble Codes (DTCs)

Your mechanic will check for any related trouble codes with an OBD-II scanner. Some noteworthy check engine codes include:

DTC P1516: A DTC P1516 indicates a problem with the throttle actuator control (TAC) system, which can limit your vehicle’s speed. It may be due to a faulty TAC module or accelerator pedal position sensor.

DTC P2135: A DTC P2135 indicates a problem with the throttle position sensor or the A/B voltage correlation, often leading to reduced engine power. Some of its triggers include throttle position sensor or accelerator pedal position sensor failure. 

➤ DTC P0856: This code points to problems with the traction control input signal. A faulty traction control system triggers the code, which activates limp mode and reduces your car’s speed.

2. Replace Faulty Components

When the reduced engine power light is triggered, it’s crucial to diagnose the faulty components through proper testing and replace them immediately. 

The common culprits include:

3. Clean Components

The reduced engine power issue could be due to clogged or contaminated components. Cleaning the throttle body, spark plugs, catalytic converter, and other relevant parts can improve functionality and resolve the engine light problem.

4. Reset ECU

Disconnecting the vehicle’s battery for a few minutes can reset the system and erase stored error codes. This simple trick helps in cases where temporary glitches trigger the reduced engine power mode. 

However, if the underlying issue persists, it may result in the Check Engine Light appearing. In such cases, it’s best to let a mechanic diagnose and address the issue.

Next, let’s dive deeper and explore some queries about this engine light. 

3 FAQs about Reduced Engine Power Light 

Here are answers to common questions about the reduced engine power light:

1. Is it Safe to Drive with Reduced Engine Power Warning Light?

Yes, driving with the reduced engine power warning light is safe, but only for short distances. 

Most likely, your vehicle will go into reduced power mode. This can mean reduced control over your vehicle, which can be worrisome in unpredictable situations on the road.

2. How Much Does it Cost to Fix Engine Power Reduction?

The cost to fix engine power reduction can vary based on the underlying cause and the make and model of your vehicle.

Here are cost estimates for some fixes:

3. Can You Bypass Reduced Engine Power Warning Lights?

Yes, you can. The simplest way to bypass reduced engine power warning lights is to use the OBD-II scanner to reset the ECU. But, removing the vehicle from reduced power mode is much more complicated, as it requires you to solve the underlying problem.

Final Thoughts 

Engine-related malfunctions can trigger the reduced engine power warning light, which helps safeguard your vehicle from further engine damage. 

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