What Does The Reduced Engine Power Warning Mean?

Reduced Engine Power Warning Light

The reduced engine power warning light indicates that the vehicle's computer system has intentionally reduced your vehicle's engine performance.

Reduced engine power occurs when the vehicle's computer receives a signal indicating a problem from one of its sensors.

It lets you safely get to a professional mechanic while hopefully minimizing further damage.

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    Reduced Engine Power Warning Meaning

    Reduced Engine Power Warning Light On Instrument Cluster
    Reduced Engine Power Warning Light On Instrument Cluster

    The Reduced Engine Power warning light is activated by your vehicle's computer system when it detects a failure in one of the vehicle's components.

    The reduced engine power mode is often called "limp mode."

    When your vehicle enters reduced engine power mode, the engine's performance is inhibited. As a result, it can cause your car to suddenly lose power.

    It is built into your vehicle to prevent severe damage to your vehicle's components by allowing you to get your car to a mechanic to get it checked out.

    Occasionally, the fuel system may be disabled, requiring a tow, so it's important to troubleshoot the problem and get it fixed as soon as possible.

    Can I Drive With Engine Power Reduced Light?

    You can drive with the engine power reduced mode, but it is not ideal and should be kept to a minimum for several reasons.

    First, you could be causing damage, leading to an even more expensive fix in the future.

    It could be the case if the engine power reduced mode is triggered by low transmission fluid.

    Second, low engine power can be dangerous in situations like driving on a high-speed highway or freeway.

    Causes of Reduced Engine Power Warning

    There are many reasons why your reduced engine power light came on, and we will go over some of them in this article.

    This list is by no means exhaustive, and you should take your vehicle to a qualified professional as soon as possible if you are unqualified to diagnose the problem.

    Further down the article, we go over some standard OBD2 codes and their meaning.

    Loose Connection

    Modern vehicles are controlled by computer modules that retrieve information from sensors throughout the car.

    Wires connect the sensors and computer modules.

    A loose connection prevents the computer and sensors from communicating correctly.

    A damaged wire can cause a short that will trigger the engine to reduce power mode.

    Poor connections and improperly secured ground wires will also cause the engine to throw a code.

    Wiring problems can be extremely time-consuming to find.

    A proper system scan with an OBD2 sensor can point you in the right direction.

    Defective Oxygen Sensor

    Oxygen Sensor On Modern Car
    Oxygen Sensor On Modern Car

    The engine's oxygen sensor measures how much oxygen flows through the vehicle's exhaust system.

    It helps the vehicle's computer adjust the intake air-fuel mixture to maximize the engine's efficiency.

    A malfunctioning oxygen sensor will send inaccurate information back to the computer, causing your vehicle to run improperly and leading to a reduced engine power warning light.

    Malfunctioning Computer System

    The computer system is the backbone of a modern vehicle.

    It consists of various modules and sensors that send them data working together to keep the vehicle operating as efficiently as possible.

    It all happens in real-time with thousands of data points per second.

    A failing component in the computer system can lead to countless issues. Any of which can trigger the engine power reduced mode.

    Failing Mass Airflow Sensor

    A bad mass airflow sensor measures the pressure and density of the air that enters the engine.

    This data aids the computer in maintaining the proper air-fuel mixture.

    Clogged Catalytic Converter

    Catalytic Converter Cutaway
    Catalytic Converter Cutaway

    The catalytic converter is part of the vehicle's exhaust system.

    The catalytic converter converts toxic exhaust gasses into somewhat less poisonous gasses.

    Over time the catalytic converter can become clogged and stop functioning correctly.

    It may prevent the vehicle from passing emissions and trigger a warning light.

    Transmission Failure

    Removing Transmission Oil Pan
    Removing Transmission Oil Pan

    Problems with the transmission, such as a low fluid level or a clogged transmission oil filter, can put the vehicle in reduced engine power mode.

    It is to minimize severe transmission damage if the transmission starves of oil at full speed.

    Idle Relearn Procedure Needed

    Vehicles such as the GMC Yukon and Chevy Malibu may have to go through an engine relearn process when maintenance such as cleaning or replacing the throttle body has been performed.

    If an idle relearn process is not performed, the vehicle may enter reduced engine power mode.

    Cooling System Issues

    Engine Overheating With The Hood Up
    Engine Overheating With The Hood Up

    If a vehicle's engine starts to overheat, the car may enter reduced engine power mode to prevent the engine from revving too high and further exacerbating the problem.

    Failed Pedal Position Sensor

    The foot pedal uses sensors to measure its relative position.

    The vehicle's computer uses this data to calculate the desired throttle response from the vehicle's engine.

    A failed pedal position sensor will put the vehicle into reduced engine mode.

    Can needing an oil change cause reduced engine power?

    It is improbable that needing an oil change is the cause of a reduced engine power warning.

    Can spark plugs cause reduced engine power?

    Spoiled Spark Plug
    Spoiled Spark Plug

    Faulty spark plugs can trigger reduced engine power mode.

    Spark plugs are a critical part of your vehicle's ignition system, and if one or more is not working correctly, it could put your car in reduced power mode.

    Can You Fix Reduced Engine Power Yourself?

    The best place to start first is to do a diagnostic test with an OBD2 scanner.

    The OBD2 tool pulls the trouble codes from your vehicle's system and displays them on its screen.

    OBD2 scanners can be pretty inexpensive and can save you time and money from "throwing parts" at the problem in hopes of fixing it.

    BONUS: It's also nice to mention to a mechanic, who is perhaps a bit unscrupulous, that you have the trouble code to prevent him from trying to give you the "runaround."

    How To Fix Reduced Engine Power

    As mentioned above, the best place to start is with an OBD2 scanner.

    A basic one is inexpensive and can point you in the right direction.

    If the problem is something like a dirty gummed up throttle body or a bad O2 sensor, it can be fixed by yourself with essential hand tools.

    Unfortunately, often the problem will be more complicated and should be fixed by a professional mechanic at a licensed automotive repair shop.

    Check for Diagnostic Trouble Codes (DTCs)

    Checking Trouble Codes On OBD2 Scanner
    Checking Trouble Codes On OBD2 Scanner

    Follow your OBD2 tools' instructions to pull the trouble codes from your vehicles.

    The codes below are standardized across the automotive industry by the Society Of Automotive Engineers.

    Trouble Code Trouble Code Meaning
    P0120 Throttle/Pedal Position Sensor/Switch “A” Circuit
    P0121 Throttle/Pedal Position Sensor/Switch “A” Circuit Range/Performance
    P0122 Throttle/Pedal Position Sensor/Switch “A” Circuit Low
    P0123 Throttle/Pedal Position Sensor/Switch “A” Circuit High
    P0220 Throttle/Pedal Position Sensor/Switch “B” Circuit
    P0221 Throttle/Pedal Position Sensor/Switch “B” Circuit Range/Performance
    P0222 Throttle/Pedal Position Sensor/Switch “B” Circuit Low
    P0223 Throttle/Pedal Position Sensor/Switch “B” Circuit High
    P0638 Throttle Actuator Control Range/Performance
    P0639 Throttle Actuator Control Range/Performance
    P2100 Throttle Actuator Control Motor Circuit/Open
    P2101 Throttle Actuator Control Motor Circuit/Open
    P2105 Throttle Actuator Control System - Forced Engine Shutdown
    P2119 Throttle Actuator Control Throttle Body Range/Performance
    P2120 Throttle/Pedal Position Sensor/Switch “D” Circuit
    P2122 Throttle/Pedal Position Sensor/Switch “D” Circuit Low Input
    P2123 Throttle/Pedal Position Sensor/Switch “D” Intermittent
    P2125 Throttle/Pedal Position Sensor/Switch “E” Circuit
    P2127 Throttle/Pedal Position Sensor/Switch “E” Circuit Low Input
    P2128 Throttle/Pedal Position Sensor/Switch “E” Circuit High Input
    P2135 Throttle/Pedal Position Sensor/Switch “A”/”B” Battery Correlation
    P2138 Throttle/Pedal Position Sensor/Switch “D”/”E” Battery Correlation
    P2176 Throttle Actuator Control System - Idle Position Not Learned

    How Much Does It Cost To Fix Engine Power Reduced Mode?

    The cost to fix engine power reduced mode can vary greatly depending on the problem. For example, a loose connection may cost $0, while a lousy transmission can cost over $3000.

    Conclusion

    There is no need to panic when the reduced engine power light comes on. But it is crucial to get your vehicle to a mechanic as soon as possible.

    There are quite a few reasons why the reduced engine power light is showing, ranging from loose wires to a bad transmission.