What causes a vehicle to go into reduced power mode?

Reduced power mode, commonly called limp mode, occurs when the car's engine control unit detects a fault and limits engine output to protect the engine and drivetrain.

In practice, the system may throttle back fuel delivery, restrict turbo boost, or disable nonessential systems so you can reach a repair facility. Causes span from engine misfires and sensor faults to fuel delivery problems, exhaust restrictions, and transmission faults.

Common triggers: engine management and sensors

These are the kinds of faults the ECU looks for that can trigger reduced power mode.

• Engine misfire or ignition faults, which disrupt smooth operation and can trigger safety limits.


• Low fuel pressure or failing fuel pump, causing lean or incomplete combustion.


• Airflow restrictions or a dirty air filter, reducing the amount of air reaching the engine.


• Faulty mass air flow (MAF) sensor or manifold absolute pressure (MAP) sensor readings.


• Faulty oxygen sensors or catalytic converter issues that upset the fuel–air mix or exhaust flow.


• Throttle body or accelerator pedal position sensor problems that impair throttle response.


• Turbocharger boost problems or restricted intercooler in turbocharged engines that limit power.


• Coolant temperature sensor misreadings that keep the engine running with overly rich or lean fuel mixes.


• Position sensor faults for crankshaft or camshaft that confuse engine timing.


• Vacuum leaks or cracked hoses that create lean conditions.

Diagnostics typically rely on reading fault codes with an OBD-II scanner and inspecting related systems. A mechanical check is often needed to confirm the exact cause.

Transmission and drivetrain triggers

Some reduced-power conditions involve the drivetrain and transmission, which may limit output to protect the gears and torque converters.

• Transmission slipping or low fluid level that impedes engagement and torque transfer.


• Overheating transmission or a failing torque converter, triggering protective limits.


• Wheel speed sensor or ABS-related faults that trigger control systems to limit power.


• Faulty transmission control module or gear selector issues affecting performance.

These issues often coincide with shifting problems or warning lights. A professional diagnosis can confirm whether the problem lies in the transmission or elsewhere in the powertrain.

Other factors

Environmental and operational conditions can also trigger reduced power mode in some vehicles.

• Engine overheating or coolant loss that risks engine damage if power is not reduced.


• Low or fluctuating oil pressure or oil level that can warn to protect engine components.


• Electrical faults, battery voltage drop, or alternator problems that affect engine control modules.


• Exhaust restrictions such as a blocked diesel particulate filter (DPF) or catalytic converter backpressure, especially in diesels.

Modern cars tie many fault conditions to limp mode to protect critical components and give drivers a safe path to service.

What to do if you notice reduced power

If you experience reduced power, take these steps to stay safe while you diagnose and plan repair.

1. Find a safe place to pull over and, if needed, switch to a lower speed and turn on hazards.


2. Check for warning lights, abnormal noises, overheating, or smoke, and note symptoms or smells.


3. If you have an OBD-II scanner, read any stored fault codes and record them for a technician.


4. Check fluid levels (engine oil and coolant) once the engine is cool, and look for leaks or obvious issues.


5. Do not try to diagnose or bypass the fault; if you’re not certain, arrange roadside assistance or tow to a shop.

Limp mode is a safety feature, not a fix. A proper diagnosis is required to restore full performance and prevent future damage.

Summary

Reduced power mode, or limp mode, is triggered by the vehicle’s onboard computer in response to faults or unsafe conditions. It limits power and RPM to protect the engine and drivetrain, with common causes including misfires, fuel and air delivery problems, sensor failures, exhaust restrictions, and transmission faults. A systematic diagnosis using fault codes and professional inspection is typically required to identify and fix the underlying issue.

Can I drive my car if it says engine power reduced?

You can drive a short distance to a repair shop, but it is not recommended to drive for long distances. The "engine power reduced" message means the car is in a protective "limp mode" to prevent further damage, which can be unsafe, especially on highways, and could lead to more expensive repairs. It's best to pull over when it's safe, turn off the engine, and have the car towed to a mechanic for diagnosis and repair. 
Why you should avoid driving long distances

• Risk of further damage: Continued driving can worsen the underlying problem and lead to more expensive repairs. 
• Safety concerns: The car will have limited acceleration and speed, which can be dangerous on busy roads or highways. 
• Sudden failure: The car could stop running completely, leaving you stranded in an unsafe location. 

What to do immediately

1. Find a safe place: Pull over to the side of the road as soon as you can do so safely. 
2. Turn off the engine: This allows the system to cool down and can sometimes temporarily reset the mode. 
3. Assess the situation: If the message disappears after restarting, you may be able to drive a short distance to a mechanic. If it reappears, or if you are in a dangerous spot, do not drive further. 
4. Call for professional help: Contact a tow truck to get your car to a repair shop for a professional diagnosis and fix. 

What is the most common reason for reduced engine power?

The most common reason for reduced engine power is a dirty or malfunctioning throttle body, which can lead to restricted airflow. Other frequent causes include faulty sensors (like the mass air flow or accelerator pedal position sensor) and issues with the fuel or exhaust systems.
 
Common causes for reduced engine power

• Throttle body issues: Carbon buildup or a faulty throttle body or its position sensor can prevent proper airflow, forcing the car into "limp mode" to protect the engine. 
• Faulty sensors:
  • Mass Air Flow (MAF) sensor: Measures the air entering the engine, and a malfunction can lead to an incorrect air-fuel mixture. 
  • Accelerator Pedal Position (APP) sensor: If this sensor sends incorrect data, the engine control module (ECM) may restrict power. 
  • Other sensors: Faulty oxygen (O2) sensors, crankshaft sensors, or camshaft sensors can also trigger the condition. 
• Fuel system problems: A clogged fuel filter, dirty fuel injectors, or a failing fuel pump can starve the engine of the fuel it needs to operate at full power. 
• Exhaust system problems: A clogged catalytic converter is a common cause, as it can create excessive backpressure in the exhaust. 
• Transmission or engine malfunctions: The ECM may limit power if it detects a serious problem with the engine or transmission. 
• Overheating: A faulty cooling system can cause the engine to overheat, prompting the system to reduce power to prevent further damage. 

How do I fix reduced engine power mode?

To fix an "engine malfunction reduced power" warning, first safely pull over and restart the vehicle as a temporary fix. If the light returns, diagnose the issue by scanning for error codes and checking for problems like a clogged air filter, faulty sensor (like the MAF or O2), or dirty throttle body, which can often be cleaned or replaced. For more complex issues, such as fuel system problems, catalytic converter clogs, or transmission issues, it may require professional diagnosis and repair. 
Initial checks and resets 
This video explains the initial steps to take when you see the "Engine Malfunction Reduced Power" warning: 1mPete's GarageYouTube · Jan 28, 2023

• Pull over safely: Find a safe place to stop your vehicle. 
• Restart the engine: Turn the car off completely, wait a minute, and then restart it. This can sometimes clear a temporary issue. 
• Check gauges: Look at your temperature and pressure gauges to see if the engine is overheating or if oil pressure is low. 
• Inspect fluids: Check your engine oil, coolant, and transmission fluid levels. 
• Scan for codes: Use an OBD-II scanner to get a more specific diagnosis by reading the diagnostic trouble codes (DTCs). 

Common causes and fixes

• Clogged air filter: A simple fix is to check and replace a dirty air filter, which restricts airflow to the engine. 
• Faulty sensors: Problems with the Mass Air Flow (MAF) sensor or Oxygen (O2) sensor can cause issues. A faulty throttle position sensor is also a common culprit. 
• Dirty throttle body: The throttle body can get dirty, restricting airflow. Cleaning it may solve the problem. 
• Fuel system issues: A clogged fuel filter, weak fuel pump, or dirty fuel injectors can starve the engine of power. These components may need to be cleaned or replaced. 
• Exhaust blockage: A clogged catalytic converter can cause significant performance loss. This requires professional diagnosis and may need replacement. 
• Electrical issues: Check for loose or corroded battery cables and wiring, as these can cause erratic sensor readings. 
• Engine overheating: Low coolant levels or a failing cooling system component like the thermostat can trigger the warning to protect the engine. 
• Transmission problems: Issues with the transmission, either mechanical or sensor-related, can cause the car's computer to reduce power. 
• Failing ECM: Though less common, a faulty Engine Control Module (ECM) can also be the cause. 

When to seek professional help 
This video discusses the common causes of "Engine Malfunction Reduced Power" and what to do: 1mNexologyYouTube · Aug 12, 2025
Some issues, such as those involving the transmission, catalytic converter, or ECM, often require professional expertise and tools. If the simple fixes don't resolve the problem, or if you're uncomfortable performing the checks, it's best to consult a qualified mechanic. 
You can watch this video to see how a dirty throttle body can cause the "Engine Malfunction Reduced Power" warning and how to clean it: 1mMatt's ShopYouTube · Jun 13, 2025

Why did my car go into low power mode?

Defining “Reduced Engine Power”
Several things can trigger limp mode, including loose cables, low coolant, fluid, or oil levels, transmission errors, internal engine issues, and failing sensors. Any problem with shift solenoids, pressure valves, and heat will cause the transmission to go into limp mode.