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Friday, February 23, 2024

What Does Reduced Engine Power Mean

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Reduced engine power, a phrase that many vehicle owners dread, is something that should never be ignored. It represents a vehicle’s response to a potential problem within its system, designed to protect the engine from serious damage. This safeguard, while frustrating to the driver, indicates that your vehicle’s computerized system has detected a problem that could harm the engine if ignored.

What is Reduced Engine Power?

Reduced engine power, also often referred to as ‘limp mode’, is a protective feature incorporated into vehicles. It activates when the car’s computer system (ECU or PCM) recognizes a fault within the engine or its related components. When the ECU determines that there’s an issue which might lead to significant engine damage, it limits the vehicle’s power output to minimize stress on the engine. This reduced power ensures that the vehicle can still be driven, but at a much lower speed, hence the term ‘limp mode’.

What Exactly is Reduced Engine Power Warning?

The Reduced Engine Power warning is an alert that appears on your vehicle’s dashboard. The vehicle’s onboard computer system, known as the powertrain control module (PCM), activates when it detects a potential issue that could potentially harm the engine, initiating a warning or alert. The warning serves as a protective mechanism. When a problem is identified, the PCM immediately limits the vehicle’s power output to prevent further damage to the engine. This results in a considerable reduction in the car’s performance, including slower acceleration and reduced top speed, essentially forcing the vehicle into a ‘limp mode.’

Common triggers for this warning can be anything from a malfunctioning sensor, such as the throttle position sensor or oxygen sensor, to issues with the fuel system, transmission, or even wiring problems.

When you see a Reduced Engine Power warning, it’s a clear sign that your vehicle needs immediate attention and potentially professional servicing to diagnose and address the underlying problem before it leads to more serious engine damage. 

What Causes Reduced Power Light to Come on?

The Reduced Power Light is triggered when your vehicle’s Powertrain Control Module (PCM), the onboard computer, detects an issue potentially harmful to the engine. Sensor Malfunctions, Sensors like the Throttle Position Sensor, Mass Airflow Sensor, or Oxygen Sensors monitor engine performance. Faults in these sensors can trigger the light. Mechanical Issues, Problems with the fuel pump or transmission, leading to poor engine performance, can cause the light to come on. Electrical Disruptions, Faulty wiring disrupting the electronic signals within the vehicle can also activate this warning. Powertrain Control Module Errors, The PCM itself can have errors, leading to false alarms.

What Happens When Reduced Power Light is on?

When your vehicle’s Reduced Power Light is on, it signifies the car has entered a protective state called “limp mode.” This mode triggers when the onboard computer, the Powertrain Control Module (PCM), detects an issue potentially harmful to the engine. In this state, your vehicle’s performance drastically decreases, limiting speed and acceleration. Although the car is still drivable, it will not perform as usual. This limitation is designed to prevent further damage, allowing you to safely navigate to a mechanic or service station. It’s crucial to get professional help promptly when this light appears, as overlooking it could lead to serious, costly repairs.

Is it Safe to Drive with Reduced Engine Power?

While you can technically drive with reduced engine power, it’s not recommended. This mode, also known as “limp mode,” limits vehicle performance to prevent further engine damage. Prolonged driving in this condition could lead to more severe issues. If you see this warning, it’s best to safely stop and seek immediate professional help to avoid costly future repairs.

How to Reset a Reduced Engine Power Light

Resetting the Reduced Engine Power Light involves several steps:

  1. Switch off the engine and let it rest for a few minutes.
  2. Remove the negative terminal for about 15-20 minutes. This should reset the car’s computer.
  3. Start the engine after reconnecting the battery. The light should be off.

Reduced Engine Power Trouble Codes

When your vehicle’s computer system (Powertrain Control Module or PCM) detects a problem that could potentially lead to reduced engine power, it generates and stores specific Diagnostic Trouble Codes (DTCs). These DTCs help identify the source of the problem. They can be read using an OBD-II (On-Board Diagnostic) scanner, which accesses the PCM.

Here are some common DTCs that could indicate issues leading to reduced engine power:

  1. P0121-This code indicates a problem with the Throttle/Pedal Position Sensor/Switch “A” Circuit Range/Performance.
  2. P0122-This code is triggered when the Throttle/Pedal Position Sensor/Switch “A” Circuit is low.
  3. P0222-This code points to an issue with the Throttle/Pedal Position Sensor/Switch “B” Circuit Low Input.
  4. P1125-This code is generated when there’s a problem with the Throttle Control System.
  5. P2135-This code indicates a problem with the Throttle/Pedal Position Sensor/Switch “A” / “B” Voltage Correlation.

Each of these codes points to potential issues with the throttle body, the throttle body sensor, or the pedal position sensor all of which could lead to reduced engine power.


The Reduced Engine Power light is a critical warning that safeguards your vehicle’s engine. It’s triggered when the vehicle detects potential issues that could harm the engine. The causes vary, from sensor issues to mechanical or electrical problems. Upon activation, the vehicle enters a “limp mode,” limiting its performance to prevent further damage. It’s crucial to get your vehicle inspected by a professional as soon as this light appears to prevent serious damage and ensure your safety.


How do you fix engine power is reduced? 

Repairing reduced engine power involves professional diagnosis and targeted repairs based on the problem’s nature, typically detected using an OBD-II scanner.

Can I drive with engine power reduced? 

You can technically drive with reduced engine power, but it’s not recommended. Your vehicle will be in “limp mode,” limiting its performance to prevent further damage. Seek professional help immediately.

Why did my car say engine power was reduced? 

This warning appears when your vehicle’s system detects an issue that could damage the engine or impair its performance. Causes can range from sensor faults to mechanical problems.

Is reduced engine power serious? 

Yes, it’s a significant issue indicating potential engine damage or impaired performance. Immediate professional attention is required to prevent further complications.

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