In this guide, we will be answering a frequently asked question by vehicle owners: how much does it cost to fix reduced engine power? In reduced power mode, the engine is notably weaker and is missing speed while trying to accelerate. However, you may see a ‘Reduced Power Mode Sign’ on the dashboard along with the check engine light.
So, how much does it cost to fix reduced engine power? The cost to fix reduced engine power typically ranges from $150 to over $2500, depending on the severity of damage, engine design, and regional labor costs. Reduced power is often caused by wiring harness issues, low oil or coolant pressure, ignition problems, throttle body malfunctions, emission failures, fuel delivery faults, spark plug or valve defects, timing belt damage, transmission issues, or malfunctioning sensors like the throttle position, O2, MAF, or accelerator pedal position sensors.
The labor cost to replace the engine component can vary depending on how it is difficult to remove the damaged component. Sometimes, different tools and different levels of torque are required to unbolt a specific engine component. Moreover, some engine components like oil pressure sensors or fuel rail are not easily accessible.
You have to remove several engine parts without damaging the engine’s wiring to access them. This is where the skill of a mechanic comes into play, due to which professional mechanics charge higher prices to fix reduced engine power. Here, your negotiation skills will play a huge role to cut those costs.
Furthermore, the cost of engine parts depends on the manufacturer. OEM engine sensors or engine components are usually expensive as compared to aftermarket engine parts. It is always recommended to install OEM sensors, spark plugs, and fuel injectors. The cost will be a bit higher but your engine will provide optimum performance.
What You Will Learn:
Reduced Engine Power Mean
Reduced engine power means that the engine is not producing its maximum power output at a certain engine RPM or the engine isn’t performing to the levels it should be. If the engine is operating at a higher RPM, it’s likely that the pistons aren’t moving to the level of engine power needed.
The reduced engine power mode is also called a ‘limp mode’. It’s a safety indicator vehicle manufacturers have installed to avoid further engine or transmission damage.
As a result of reduced engine power, the vehicle loses acceleration or does not go above a certain speed while you’re trying to speed up your vehicle.
If you are driving and suddenly the car starts to slow down, that is reduced engine power. It means the engine is running less efficiently and producing less power.
Engine damage can occur in many ways. The most common one is that the vehicle is not getting enough fuel. The vehicle may also be experiencing a malfunction in the engine control system.
Engine damage can also be caused by a mechanical failure of the engine itself. The other reason for engine damage is an electrical problem in the engine control unit.
Engine control unit (ECU) gets data from different engine sensors to adjust the air and fuel ratio and ignition timing. The ECU is programmed to operate the engine in a range of certain values provided by the engine sensors.
If the ECU does not find a suitable correlation in the sensors’ readings, it would send signals to automatically reduce engine power to prevent further engine damage.
Is It Safe To Drive With Reduced Engine Power?
You can drive your engine with reduced power. It wouldn’t be risky at first. But, you will not be able to enjoy the drive at higher speeds as the ECU will prevent the engine from gears shifting and will stop you from accelerating.
If that safety feature was not installed in the vehicle, you would not be able to know that your engine had a fault. As a result, driving the vehicle at higher speeds would result in subsequent serious engine failures.
An engine is a complex machine. An issue in one area of the engine might have an impact on the other area. So, if your vehicle goes into the reduced power mode, drive it slowly and take it to the trusted mechanic or dealership.
Your mechanic will have several options for your car, including fixing, replacing a part, or maintenance. You may be paying for a service that will fix the problem or that will replace or maintain the parts.
Diagnosis Of Reduced Engine Power
The first step you have to take for reduced engine power is to diagnose trouble codes stored in your engine’s memory. This helps identify the root cause of reduced engine power.
If you have an engine after 1996 year, it has an OBD2 diagnosis system that throws codes when there is a fault in the engine. You can scan those trouble codes using an OBD2 scan tool. I usually use BlueDriver. It connects with a smartphone via Bluetooth. Moreover, it’s also budget-friendly and also reads ABS and traction control codes.
One more thing I would highlight is that you could also find trouble codes like ‘P1xxx’. If there is ‘1’ after P, it means that that trouble code is manufacturer specific. It is only applied to your vehicle model. For instance, the P1026 trouble code has different meanings for the Porsche Cayman 987.2S and Ford vehicles.
However, if there is ‘0’ instead of ‘1’, the trouble code is generic and applicable to all engines.
When your engine is in reduced power mode, your scan tool may pick up the following generic trouble codes:
- Trouble codes related to vehicle driving performance (ABS coded, traction control codes)
- Trouble codes related to the transmission system (especially if your vehicle has an automatic transmission)
- Trouble coded related to emissions
- Trouble codes related to throttle body control system
- Trouble codes related to the accelerator pedal
Causes Of Reduced Engine Power
Here are the most possible causes of reduced engine power:
1. Damaged Engine Wiring Harness or Loose Harness Connectors
The most cause of reduced engine power is a damaged engine wiring harness. A properly working engine harness will contain several connections. These connections can consist of wires, plugs, cables, clips, or clamps.
Some of the main connections include:
- Spark Plug Wire
- Battery Cable
- Ignition Switch
- Throttle body actuator
- Sensors (accelerator pedal, O2, MAF, TPS, MAP)
Damaged wiring harnesses can result in a loss of electrical signals between the engine and other electrical components. For example, if the ground signal is interrupted, the engine computer will not receive information regarding coolant temperature, oil pressure, and other important parameters such as engine emissions.
How To Fix?
First, you have to locate all ground connections of your engine. Each engine has different locations of ground connections. All ground connections are linked with the negative terminal of the battery. Some engines also have ground straps in the form of braided copper.
Note: Before checking those ground connections, first, confirm that your battery is fine and has clean positive and negative terminals. Moreover, the connections of the battery are tight. A healthy engine battery should give around 12.8V when the engine is running.
After you locate ground connections, check if there is any corrosion around the bolts or if the connections are unhooked. Also, visually inspect the wires. If the insulation is broken or the wire inside the insulation is broken, it will not be able to transfer electric signals properly. In my guide about car won’t start after replacing the battery, you’ll find a section on inspecting the bad ground connections in the engine wiring harness.
After inspecting ground connections, if the issue of reduced engine power is still there, check the wiring harness connectors to fuel injectors, ignition coils, and to sensors of your engine. Carefully analyze that the wires inside the harness connectors are not pulled out of their terminals. Moreover, there shouldn’t be any moisture or corrosion on the terminals of the harness connector.
The voltage across the terminals of harness connectors of fuel injectors and ignition coils is around 12V and the voltage across the terminals of harness connectors of sensors (O2, MAF, TPS, etc) is around 5V.
2. Malfunctioning Oxygen Sensor
Oxygen sensors are responsible for monitoring the air/fuel mixture for your engine and adjusting the fuel injected accordingly.
Oxygen sensors are placed in the exhaust stream and determine how much unburnt oxygen is present in the exhaust gases. If oxygen levels are low, the sensor sends a signal to the engine computer to increase the fuel injection.
When O2 sensors malfunction, the mixture of the air and fuel becomes too rich or too lean and you end up with reduced engine performance and a higher emission level.
How to test?
To check for a faulty oxygen sensor, you can conduct a voltage test. The oxygen sensor’s voltage should fluctuate within a specific range as the air-fuel ratio changes.
If the voltage remains steady or exhibits abnormal fluctuations, the sensor is likely faulty.
Ideally, a healthy oxygen sensor should fluctuate at least once every two seconds, with a voltage range between 850mV and 150mV.
To conduct the test for oxygen sensor, connect the positive lead of a voltmeter to the sensor’s signal wire. If the sensor has two wires, connect the negative lead to the negative wire of the sensor. This will help determine whether the sensor is functioning within the expected voltage range.
How To Fix?
Replacing it with a genuine oxygen sensor is a simple repair job that can be done at home by a professional mechanic.
Vehicles have usually two oxygen sensors, each upstream and downstream of a catalytic converter on the piping of the exhaust system. The O2 sensors are likely to be stuck in the threads of the piping because of an expansion and contraction. You will need to apply a lot of torque to remove sensors. For this, you would need long socket wrenches.
Before removing the O2 sensor, make sure to check its harness connector first. After that, diagnose O2 sensors with the Bluedriver scan tool. You will find a section on bad O2 sensors diagnosis in my guide on P0171 code.
The mechanic labor cost to remove oxygen sensors and fix reduced engine power will depend on how it will difficult to access the oxygen sensors. Usually, the labor cost of an O2 sensor replacement can go up to $200. The cost of an oxygen sensor ranges between $20 and $100.
3. Bad Throttle Body and Throttle Position Sensors
Reduced engine power also indicates a fairly serious problem with the throttle body and throttle position sensors. The throttle body system includes an electronic throttle body and two throttle position sensors installed on it. Electronic throttle body has a motor (actuator) operated from DC supplied by ECU or TAC (Throttle Actuator Control) module.
TPS sensor monitors how far the throttle body is opened when an accelerator pedal is pushed. The throttle body has a throttle valve whose angle is measured by throttle position sensors. Also, note that the throttle body is only included in gasoline engines. You will not find a throttle body in diesel engines.
The ECU uses readings of two throttle position sensors to determine whether a throttle body has opened to the same position as calculated from the mass airflow reading from the MAF sensor (the MAF sensor is just before the throttle body). If the ECU does not find that a throttle angle is correct for a given reading from the MAF sensor, it would limit your vehicle to reduced power mode.
How To Fix?
If you have Chevy trucks, your scan tool can display the P1516 code. You can read my in-depth guide on P1516 code to get more idea about how to fix this code if your Chevy truck is displaying it. For bad throttle position sensors, your scan tool could read P2101, P2175, P0122, P2135 or P0222 codes.
A throttle body has a spring inside its valve that allows the valve of the throttle body to return to its previous position when the foot is lifted off the accelerator pedal.
The following conditions indicate the healthy throttle valve functioning:
- The throttle valve should be open 20-25%.
- The throttle valve should not be completely closed or completely opened more than 25%.
- The throttle butterfly valve should move freely to the open and closed position under the normal spring pressure without being bound.
- The throttle should not be free to move open or closed without spring pressure.
The average cost of replacement of a throttle body to fix a reduced engine power could be around $500. To remove the throttle body, you have to remove the air intake manifold.
To test throttle position sensors, you have to first check their harness connector through the voltmeter. After you confirm that the harness connector is fine, connect the black probe of the voltmeter to the ground and another red probe to the 5V signal wire of the connector of the TPS sensor. When the throttle body is closed, the voltage will be around 0.2V to 0.9V. As you push the gas pedal and the throttle valve is opened, the voltage should increase to 5V.
The cost to replace the throttle position sensor (labor+Part cost) and fix reduced engine power can range from $150 to $400.
4. Bad Accelerator Pedal Sensor
Like the throttle body, the accelerator pedal also has a sensor detecting the position of the accelerator pedal, determining when the accelerator pedal is depressed, and generating the necessary electrical signals to operate your engine and other systems.
By the signal from the accelerator pedal, the ECU decides the opening or closing of the throttle body. So, if the accelerator pedal sensor becomes bad, the throttle body could not be properly controlled which would result in reduced engine power.
The cost to replace the accelerator pedal sensor and fix reduced engine power ranges could range from $100 to $500, depending on the model of vehicle.
5. Malfunctioning Traction Control System
Traction control systems are responsible for preventing wheels from slipping on the road when conditions may call for it. Any issues with this system could cause decreased engine performance and/or reduced speed so that your vehicle may not slip.
Traction Control System (TCS) is responsible for controlling the braking force to prevent skidding and avoid accidents. In most cases, TCS works effectively and the vehicle stops safely.
However, there are times when the system malfunctions and makes the driver lose control. In that case, the driver will lose his/her ability to steer and stop the car. In that case, ECU puts the engine in reduced power mode to limit your speed and prevent you and your vehicle from any accidental damage.
I have explained the components of the traction control system in my guide on what does TC mean in a car. If your vehicle is also showing a message of “Service Traction Control/Service Stabilitrak” along with the reduced engine power mode, it means that the traction control system has gone bad.
How To Fix?
The problems in traction control or StabiliTrak systems can be due to:
- Bad steering angle sensor
- Bad wheel speed sensors
- Bad tire pressure monitor sensors
- Bad throttle body/sensors
- Bad wheel lateral speed sensors
- Faulty Antilock Braking System (ABS)
So, the cost to fix the Traction control/StabiliTrak system and reduced engine power depends on which part of that system is damaged and needs to be replaced. A wheel speed sensor replacement can cost between $250 and $600.
6. Transmission System Damage
Automatic transmission problems can cause reduced engine power. Mainly it is because of a low level of transmission fluid or its poor quality.
The transmission system consists of several components that need to work together and when one or more of them fail or malfunction, it can affect the whole system. You can learn about automatic transmission in my guide on what does low gear mean in a car.
Transmission components include the clutch and flywheel, the torque converter, the oil gear pump, the valve body, the transmission solenoid, the transmission speed sensor, the transmission case, the transmission fluid, the gears, and the differential.
To learn more about automatic transmission and its problems, you can read my guide on the causes of car not moving in any gear in automatic transmission.
When any damage occurs to transmission components, the vehicle’s computer will put the engine in reduced power mode to prevent transmission damage.
In many cases, the driver may think the vehicle is running fine until it is discovered the car is having reduced acceleration or reduced torque.
How To Fix?
To fix reduced engine power caused by transmission damage, you first have to check the level of transmission oil. Please don’t confuse it with the motor oil.
The transmission fluid dipstick is different. The transmission fluid level should be between high and low levels on the dipstick.
Healthy transmission fluid should be reddish or clear pink in color. If there are any particulates in the transmission fluid, you should change it.
Usually, engines need 5 to 15 quarts of transmission oil. For instance, for the ford F150, if you drop the transmission oil in a pan and change the filter it should be about 5-7 quarts.
If you also flush the torque converter, you’ll need 14 quarts of transmission fluid. The cost of transmission fluid could range from $50 to $200.
If the transmission oil has an optimum level, it means that one or more components of a transmission system are damaged. You should never attempt to repair an automatic transmission yourself.
Your vehicle’s automatic transmission has a sophisticated computer system, and you should never take it upon yourself to troubleshoot or perform any repairs on the system. The transmission system is incredibly sensitive, and a failure could be very costly, so you want to ensure that a certified mechanic is performing repairs on your car.
The cost to fix/repair the transmission and fix reduced engine power could range from $600 to $3000, depending on which part of the transmission system needs to be changed or the whole transmission repair is needed.
7. Clogged Air Filter
A clogged air filter can also cause reduced engine power. The air filter is present in the air box, before the MAF sensor.
When the filter becomes blocked with dirt, particles, and moisture, less air passes through the engine.
When the engine is not getting enough air, it may sound like a slow idle or rough idling. You might notice the engine is sluggish to respond to changes in throttle. When this happens, your engine may also throw the P2175 – Throttle Actuator Control System Low Airflow Detected code.
How To Fix?
Replacing an air filter is the easiest job. You can save a big labor cost by installing it yourself. You have to locate the airbox in your engine bay. There are clips on both sides of the airbox. Release the clips with your hands and lift the airbox cover.
You’ll see the air filter. Remove the air filter. Vacuum the airbox and insert a new air filter. The cost of the air filter is around $30 to $60.
8. Clogged Catalytic Converter
Reduced engine power can also be caused by a clogged catalytic converter. Catalytic converters are placed at the end of an engine exhaust system to reduce the level of toxic gases emitted into the environment.
A catalytic converter is responsible to convert harmful exhaust gases into water vapors, nitrogen gas, and carbon dioxide. When the catalytic converter is clogged, the air-fuel mixture becomes too rich, causing a build-up of carbon monoxide and unburnt fuel.
Clogged catalytic converters can also cause the engine to run too hot, leading to overheating. This can damage the engine or even cause it to fail. That’s why, when a catalytic converter is clogged, the ECU puts the engine in reduced power mode to prevent the engine parts from wearing out.
How To Fix?
Replacing a catalytic converter is not an easy job. A highly professional mechanic can do this job. The cost of a catalytic converter ranges between $500 and $2000. Moreover, the labor cost to replace a catalytic converter could also be around $150 to $500 as it takes 2 to 4 hours to replace a catalytic converter.
9. Bad MAF Sensor
A malfunctioning MAF sensor can also cause a reduced engine power. Note that the MAF sensor is not present in all engines. Instead, some engines have MAP (Manifold Air Pressure) sensors located in the air intake manifold. So, it entirely depends on the engine.
If the MAF sensor is bad, the ECU will no longer be able to determine how much air is entering the engine. As a result, the air/fuel mixture will not be properly adjusted and the engine will go into reduced power mode.
How to test?
If you want to test your MAF sensor, you can check the voltage it produces. When you press the gas pedal, more air flows through the sensor, which makes the voltage go up. When the car is not moving much, the voltage should be less than 1.0V. But when you speed up, the voltage from the MAF sensor goes up to around 1.7V.
How To Fix?
The cost of the MAF sensor ranges from $40 to over $200. The labor cost is cheaper. In total, the cost to replace the MAF sensor and fix the reduced engine power will range from $150 to $400.
However, before replacement, you can check if the MAF sensor can be fixed by simple cleaning it.
You should clean the heated element inside the MAF sensor with a special cleaner. Just make sure you don’t touch the wire. Let it dry completely before putting the sensor back in place.
10. Low Oil Pressure
The low oil pressure caused by low oil levels or clogged filters can cause the engine to enter reduced power mode.
If the engine is running fine but you notice that the car is sluggish when you step on the gas pedal, you should check the oil level. Check my guide on how far you can drive a car on minimum engine oil to learn more.
You should check if the oil pressure sensor is working properly. If it is, then you need to find out why the oil pressure is dropping.
You may have a leak caused by a loose piston ring. Another possibility is that you have a worn or damaged piston. If you are noticing an oil pressure drop, you may have a leaking head gasket.
You may also have a damaged crankshaft. I have written my guide on oil leaks in Chevy Ford 5.3L engine. You should check it.
It is also possible that you have a worn main bearing or oil pump bearing.
You can read my guide on low oil pressure at idle to learn more. By learning different causes of low oil pressure, you can estimate the cost to fix reduced engine power.
So, the total cost to fix a reduced engine power can depend on the part needed to fix or replace your engine, the extent of the damage to the engine, and the labor cost. I have listed different causes of reduced engine power and gave a price estimate of their fix so that you could get an idea.
Also, make sure that after fixing the issue of reduced engine power, clear all error codes and reset the ECU using an OBD2 scan tool.