Reduced Engine Power Message, surging idle?

What causes Reduced Engine Power Message, surging idle. Over time, carbon builds up on the electronic throttle body. This is caused by a restricted air intake due to carbon buildup that the ECM/PCM can no longer override by adjusting throttle plate angle.

  • What causes Reduced Engine Power Message, surging idle Over time, carbon builds up on the electronic throttle body. The ECM/PCM learns to compensate for the buildup by increasing the throttle plate angle to ensure the correct amount of air still enters the engine.

Why does my car keep saying engine power reduced?

“Reduced Engine Power” Message In most cases, the Engine Power Reduced warning indicates that your car’s performance has been intentionally limited. Your car’s primary computer, often known as the powertrain control module (PCM), triggers Reduced Power Mode when it detects a system failure.

How do you fix engine power reduced?

How To Bypass Reduced Engine Power

  1. Check The Cables. One of the most popular triggers of limp-in mode is loose cables, harnesses, or clamps.
  2. Check Sensors.
  3. Check The Throttle.
  4. Airflow Sensor.
  5. Electric Control Unit.
  6. Catalytic Converter.
  7. Check Battery.
  8. Transmission Fluid.

Can a bad catalytic converter cause reduced engine power?

The reduced engine power warning is often caused by bad engine sensors like a bad oxygen sensor, MAF sensor, or a bad throttle body. It can also be caused by a loose connection to any of these sensors. A clogged catalytic converter is also often to blame.

Can spark plugs cause reduced engine power?

When a spark plug fails to fire, it can cause simple to serious problems. A misfiring engine means the spark plug wires are not firing properly. This causes many problems, like increased exhaust emissions, reduced fuel economy, and reduced engine power.

Can you drive with engine power reduced?

Can you drive safely with the Reduced Power Light on? It depends on the cause of the reduced power. Often, the problems are minor. In rare cases, though, reduced power can cause more serious problems like a seized engine, or even an electrical fire.

Can low oil pressure cause reduced engine power?

When engine oil pressure drops, friction between different parts increases. This results in a steep decline in engine performance. Watch out for common signs of decreased engine performance such as a reduction in fuel economy, loss of power, and engine stalling.

How do I bypass limp mode?

How To Bypass Limp Mode? The Step-By-Step Process

  1. Apply The Brakes. The first step to deactivate the limp mode is to apply the brakes and make a stop at a safe spot.
  2. Deploy A Car Diagnostic Scanner.
  3. Battery Disconnection.
  4. Scrutinize Automatic Transmission Fluid.

What does service traction control engine power reduced mean?

Hi There, The Stability Track light relates to the vehicles traction control system. When the computer detects an issue with this system, it will often times put the vehicle into a reduced power phase in an effort to prevent further damage and to keep the passengers safe.

What does limp mode mean?

Also known as ‘limp home mode ‘, limp mode is a security feature in cars which activates when the engine or transmission control unit picks up a fault. Once it detects a problem, limp mode will cause the less important parts of the car, such as air conditioning, to switch off, and the speed of the car will be reduced.

The “Reduced Engine Power” Message and Fixes for it

Dan Ferrell is a writer who specializes in do-it-yourself auto maintenance and repair. In the field of automation and control technology, he holds credentials. A multitude of problems might result in the notice “Reduced Engine Power.” Thanks to RudolfSimon for his contribution to Wikipedia. Reduced Engine Power (REP, limp-in mode) is a state of affairs in which your car’s computer puts your engine into when it detects one or more probable issues. Most of the time, this is caused by a problem with the electronic throttle control (ETC) system.

  • Circuit failure in the throttle control system
  • Accelerator pedal position sensor
  • Clutch position sensor
  • Electronic throttle control (ETC) system
  • Throttle position sensor A problem with the cooling system
  • Timing belt, transmission speed sensor, catalytic converter, and oxygen sensor are all examples of automotive components. Problems with the data network (module)

Some models coping with this issue may still be able to move at extremely low rates, but others may not be able to move at all and may not be able to move at all.

1. What a Reduced Engine Power Light Means
2. ETC Related to Reduced Engine Power Issues
3. How an ETC System Works
Video: A Lexus Electronic Throttle Control (ETC) System
4. Trouble Codes Related to Reduced Engine Power
5. An Automatic Transmission in Limp-In Mode
6. Known Problems Causing REP in Some Models
7. Can You Fix a Reduced Engine Power Issue at Home?
8. Video: Fixing a 2007 Chevy 2500 HD with a “Reduced engine power” message.
9. Cleaning the ETC Body and Valve

Issues with throttle control systems are a typical source of Reduced Engine Power problems in vehicles. The image is courtesy of Musay16 on Wikimedia Commons.

1. What a Reduced Engine Power Light Means

When your engine or transmission enters limp-in mode, it works at a reduced level of performance and functionality. When the ECM or transmission control module (TCM) identifies a major problem with a crucial sensor, circuit, engine control, or transmission component that requires immediate care, this restricted mode is meant to assist the driver in getting to a service facility. It is common for a REP light to illuminate with a check engine light (CEL) and, in certain instances, a Service Traction Control message to appear.

An anti-lock braking system (ABS) controller is required in order to download fault codes connected to the traction control system (TCS).

Faults in the ETC system are responsible for a large number of Reduced Engine Power (REP) warning lights.

As a driver, you may have noticed one or more of the following concerns with driving maneuverability:

  • When the engine is running between 1200 and 1600 RPM, the speed is lowered. Poor reaction from the accelerator pedal
  • The cruise control system has been disengaged. The check engine light is illuminated.

The ETC issue will also cause the REP message to appear on the dashboard as a result of the malfunction.

Read More from AxleAddict

Various manufacturers, on the other hand, respond to the REP message in different ways. As an illustration:

  • Most General Motors cars have a reduced power light. Some Chrysler vehicles have a red lightning bolt insignia on them. Some Ford model automobiles are equipped with a wrench symbol light.

3. How an ETC System Works

The following video provides an overview of the operation of an electronic throttle control system, as well as how it detects and reports on fault conditions. This particular model is from Lexus, but the same fundamental concepts apply to other makes and models as well.

A Lexus Electronic Throttle Control System

Trouble codes are available for download, and they might assist you in locating the root of the problem.

The image is courtesy of Saitobesho on Wikimedia Commons. It’s possible that a Reduced Engine Power notice may show along with the following issue code in the ECM’s memory, depending on your vehicle’s model and the malfunction identified by the computer:

  • P0120-P0124. These codes indicate that there is a problem with the throttle position or pedal position sensor, or with the circuit
  • P1125 indicates that there is a problem with the circuit. The faulty system or component varies depending on the make and model (additional codes may include: P1276, P1281, and P1286)
  • P1512Minimum Throttle Position Not Learned
  • P1516.Chevrolet – Throttle Actuator Control Module Throttle Actuator Position Performance
  • P1518.Chevrolet – Throttle Actuator Control Module Throttle Actuator Position Performance
  • P1519.Chevrolet Depending on the make and model, the faulty system or component may be different. P2111.Throttle actuator control system is stuck open
  • P2135.Accelerator pedal position (APP) / Throttle position (TP) sensor/switch A/B – voltage correlation
  • P2136.Accelerator pedal position (APP) / Throttle position (TP) sensor/switch A/B – voltage correlation
  • P2137.Accelerator pedal position (APP) / Throttle position (TP) sensor/switch A/B

On drive-by-wire systems, pay close attention to any DTCs that indicate the throttle actuator is malfunctioning. Check to see that the harness connector and wires are not broken or loosened. The Reduced Engine Power indicator will illuminate as a result of this malfunction. Engine power might be lowered as a result of difficulties with the automatic gearbox. On Wikimedia, this image is courtesy of Tokumeigakarinoaoshima.

5. An Automatic Transmission in Limp-In Mode

When an automatic gearbox enters limp-in mode, the extent to which the vehicle’s functioning is restricted varies based on the make and model of the vehicle. Your responsibilities may be restricted to the following:

  • While in Drive, only the first and third gears are available
  • There are just four gears: Park, Neutral, Reverse, and Second. Being able to drive in second or third gear at a modest speed in second or third gear It is possible that the gearbox is stuck in third or second gear.

Reduced engine power concerns have been noted in several Ford F-150 vehicles, according to reports. The image is provided of Kevauto on Wikimedia Commons.

6. Known Problems Causing REP in Some Models

If required, check with your local dealer to see if there are any service bulletins or recalls for your specific vehicle’s make and model that you should be aware of. You may also look for recalls that are particular to your car by visiting the National Highway Traffic Safety Administration’s database.

Throttle Assembly Problem in Some GM Models

Some General Motors cars have been affected by the REP problem as a result of a malfunction in the throttle assembly assembly. Most of the time, DTC P2135 will appear with the REP message. A new throttle position sensor (TPS) cover may be required for the following models, or the TPS and throttle body may need to be changed as a single unit. Aside from that, some models (from 2008 to 2010) may require the ECM to be reprogrammed. The following models are included in this classification:

  • Chevrolet TrailBlazer (2008-2009)
  • Chevrolet Tahoe Two-Mode Hybrid (2009-2011)
  • Chevrolet Silverado Two-Mode Hybrid (2009-2011)
  • 2009-2011 Cadillac Escalade Two-Mode Hybrid (2008-2009)
  • 2008-2009 GMC Envoy
  • 2008-2009 HUMMER H2
  • 2008-2010 HUMMER H3
  • 2008-2011 GMC Canyon, Savana, Sierra Denali, Yukon Denali, Yukon XL, Yu

The following engines are affected:

  • L94, LY5, L20, LMG, LC9
  • LH8, LH9, L76, LZ1, LS2
  • L96, RPO, LH6, LY6, L9H
  • LY2, L92, LFA, LMF
  • L94, LY5, L20, LMG, LC9
  • L94, RPO, LH6, LY6, L9H
  • L94,

Charge Air Cooler in the Ford F-150 (2001-2013)

Some drivers of the iconic Ford F-150 pickup truck claimed that their vehicle’s engine power would suddenly decrease when traveling at highway speeds a few years ago, prompting the National Highway Traffic Safety Administration to launch an investigation into the issue. Models from 2001 to 2013 were fitted with a 3.5L turbocharged direct injection engine with direct fuel injection. According to company service bulletins, there are certain issues with the Charge Air Cooler (CAC). When travelling at highway speeds for an extended period of time under humid circumstances, it appears to have a tendency to gather moisture in the air.

Water Leaks and Aftermarket Equipment in Some GM Models

Some of these vehicles have experienced intermittent illumination of the MIL (malfunction indication light), as well as the display of a REP message on the dashboard. The DTC P2138 is often triggered by the problem (Accelerator Pedal Position sensor issue). What causes a P2138 to occur:

  • There is a water leak that has reached the instrument panel’s body harness connector. Installation of third-party equipment.

A water leak may occur on any of the following models, depending on the exact model: If water gets into the electrical pins of a harness connector, the connector may corrode, resulting in a voltage loss. Models that were used:

  • Hummer H2 (years 2005-2009)
  • Saab 9-7X (Saab 9-7X)
  • 2005-2011 General Motors automobiles and light-duty vehicles
  • Saturn was manufactured by General Motors from 2005 to 2011. Hummer H3 from 2006 until 2010

Check all connectors and wires in the harness that might have caused a Reduced Engine Power alert, as recorded by the ECM, with great care.

The image is courtesy of Zuzu on Wikimedia Commons.

7. Can You Fix a Reduced Engine Power Issue at Home?

In general, a scan tool will be required in order to identify a REP problem. Many auto parts stores will download the DTCs for you if that is what you need them to do. You can, however, still undertake certain inspections on your own if you feel it is essential. In order to diagnose the ETC throttle while it is in operation, you should listen for any noises at idle while you or an aide depresses the accelerator pedal (if you have one). Watch what it does and take note of what it says. The presence of noise during operation indicates a faulty throttle control assembly.

If there is any carbon buildup, the throttle body and valve will need to be thoroughly cleaned out.

Components to Look Into

REP messages can be triggered in a vehicle equipped with the ETC system if any of the following conditions are met:

  • Low battery voltage
  • Failure of the ETC actuator motor
  • The throttle position (TP) sensors on both vehicles have failed. Two sensors, the TP sensor and the MAP sensor (manifold absolute pressure), are both malfunctioning at the same time. The throttle spring on the ETC has failed. Electronic throttle body barrel or valve that is dirty

Last but not least, the final piece of this tutorial goes through the basic technique for inspecting and cleaning the throttle body, if needed. With the assistance of your car repair manual, examine any of the components listed above. If you don’t already have a copy of this manual, you may get a reasonably priced copy from Amazon. Several troubleshooting and maintenance techniques are detailed in Haynes manuals, which offer step-by-step instructions. It also includes pictures and illustrations, electrical schematics, and a service schedule to make car repair and maintenance easier.

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Faulty Grounds

Many seemingly damaged parts or cables that connect the numerous sensors and actuators to the electronic control module are occasionally caused by poor engine grounds (ECM). As a result, one of the first things you should examine is the quality of the engine grounds, which includes the battery connections. Any problem with the ground connection will result in a decrease in voltage and current, which will result in a variety of driveability concerns. Check the engine grounds of your car using a digital multimeter to ensure they are in proper working order.

Then, if you discovered any DTCs, you should examine the specific component or circuit that the code refers to before replacing any other components to ensure that it is not malfunctioning.


  • Make sure there is no debris or rust on the connector once it has been unplugged. Make a jerking motion with the wires on the harness connection to check for any loose wires. Make sure both ends of the wires are properly connected by inspecting the connectors on both ends of the wires

See how a faulty wiring resulted in a Reduced Engine Power notice appearing in a 2007 Chevrolet HD by watching the two movies below.

8. Fixing a 2007 Chevy 2500 HD With a “Reduced engine power” Message

Even those versions equipped with an ETC system require periodic cleaning of the body and valves in order to function properly. When your home becomes filthy, you’ll most likely notice one or more of the following symptoms:

  • Stuttering while coming to a complete halt due to a rough idle or low idle speed

For any warnings or particular cleaning procedures for the ETC body and valve, consult your car’s owner’s handbook or vehicle maintenance manual for guidance.

In general, the following cleaning technique might be followed:

  1. Remove the ignition key from the ignition switch. Take precautions to ensure that no one else has access to the key and unintentionally attempts to switch it on. It is possible that the ETC motor may become “alive” and will chop off one of your fingers if it becomes stuck between the valve blade and the throttle body barrel
  2. Obtaining access to the throttle valve requires that the air input hose and air duct be disconnected from the throttle body. Throttle body cleaner should be soaked into a shop cloth. Remove varnish and carbon deposits from the inside of the throttle walls, as well as the area surrounding and beneath the throttle valve, with a shop rag. It is not recommended to spray cleaning straight into the ETC body. You might end up damaging a sensor. Reinstall the air duct and the air intake hose if necessary. If a throttle body relearn process is required, refer to your vehicle’s repair manual for the instructions to be followed. This will allow the car’s computer to determine the proper throttle position and allow the engine to idle properly
  3. Nevertheless,

While the information contained within this article is factual and truthful to the best of the author’s knowledge, it should not be used as a substitute for formal and personalized counsel from a competent expert. Dan Ferrell is a 2019 alumnus.

Reduced Engine Power – Limp Mode – What Does It Mean – Causes

Engine Power Decreased – Limp Mode – What Does It Mean – What Causes It

Reduced engine power, can have many different names; depending on the year, make and model of your vehicle.

As a result, the “reduced engine power” warning light on your dashboard indicates that the performance of your car has been restricted in order to avoid injuring its engine. Your car may be equipped with a plethora of control modules that monitor data from a variety of sensors and actuators in various locations. As a result, as long as these values are consistent with what it would ordinarily anticipate, it will function appropriately. The engine’s output is reduced. In contrast, if the control module suddenly gets unbalanced signals from one of the sensors that is outside of the typical range (and hence outside the parameters anticipated from this sensor), the computer is designed to do some kind of action.

It might be something as basic as the check engine light turning on (CEL).

Consequently, anything that upsets the balance, could cause a fault; and make any number of your error lights come on. But, when the computer detects a fault that is too far out of range; it will trigger this secondary mode.

On the dashboard, a reduced engine power mode is displayed. In as a result, you may notice any of the following symptoms:

  • Reduced engine power mode
  • Limp mode
  • Fail safe mode
  • Limp home mode
  • Reduced engine power mode

In the same way that your home computer enters into safe mode, it restricts the operations that may cause more damage. The functioning and speed of your car are severely restricted when your vehicle is in this mode. Finally, this mode is meant to assist the driver in reaching a servicing facility in a safe manner. Sensors for automobiles For example, when the system detects a major problem with any of the following:

  • Sensors, circuits, engine controls, transmission components, emission controls, and brake controls are all examples of what is available.

The First Three Things You Need To Check Are:

Defective engine grounds are occasionally to blame for a variety of supposedly faulty parts or cables that appear to be connected. As a result, one of the first things you should examine is the quality of the engine grounds, which includes the battery connections. Voltage and current will drop as a result of a bad ground connection, resulting in a variety of driveability concerns. Check the engine grounds of your car using a digital multimeter to ensure they are in proper working order. This will make it simpler to identify connections that are loose, rusted, or broken.

Diagnostic Trouble Codes (DTC)s

The diagnostic trouble codes (DTCs) are the first item to look for, so examine them immediately. You can use a scan tool to obtain fault codes that are recorded in your vehicle’s electronic control module (ECM). These codes will almost always point you in the correct path when trying to figure out where the issues are.

Check For Technical Service Bulletins (TSB)s And Software Updates

Documentation pertaining to a Technical Service Bulletin (TSB) Actually, there are more considerations to consider on this subject than you may believe. Occasionally, individuals rush into a repair without thoroughly reviewing all of the necessary service documentation. TSBs (technical service bulletins) are one method to remain up to date on the latest developments in technology. Furthermore, the Transportation Safety Board (TSB) gives information on probable vehicle-related problems. As a result, a (TSB) is a communication that is used to update carmaker publications, describe part upgrades, notify of probable faults or failures, and transmit upgraded or new servicing procedures.

A Technical Service Bulletin (TSB) is not a recall; rather, it is an informational document that alerts the public to a potential risk.

Common Causes, For A Reduced Engine Power Warning Include:

  • A snag in a wire, harness, or clamp
  • Alternatively Sensors for oxygen (O2) are failing
  • The throttle position sensor (TPS) is malfunctioning
  • A problem with the throttle body
  • The mass airflow (MAF) sensor is malfunctioning
  • The electronic control unit (ECU) of the car is defective. Problems with the fuel pump
  • The catalytic converter is blocked, and the vehicle cannot be started. There is a problem with the transmission. Sensor for the location of the accelerator pedal
  • Shaky ground

Following a thorough examination of your car, it should be very simple to determine the source of the malfunction. Troubleshooting Engine Error Codes


Many of the factors that contribute to decreased engine power are concerns that must be addressed as soon as possible. This, however, should not be seen as a reason for alarm. As a result, with a little investigation and some fundamental knowledge, the majority of these problems may be resolved.

Taking your vehicle to a mechanic will cost a little more than making the repair yourself.But, the benefit of their advanced scan tools; will save you time and prevent any mistakes you might make.

So, just keep in mind the fundamentals. Is there a snag in the wire? Is it possible that a vacuum line has come undone? When faced with a straightforward situation, do not seek a convoluted answer. Also typical is having a problem in one area that has an affect on three or four other areas at the same time. Thank you very much!

High Idle After Cleaning Throttle Body & “REDUCED ENGINE POWER” Fixed!

After over a week of attempting to repair my car, which began with REDUCED ENGINE POWER and progressed to a high Idle issue (P0102) (OBD2 indicates “Replace MAF sensor”), it is again operational and returns very promptly to a normal idle speed of around 800 rpm. UPDATE1st: Because this is a continuous story, I’ll keep updating this until either the car is fixed or the entire post is deleted! Yeesh, that’s hilarious! A SHORT STORY ABOUT: Cleaning the throttle body (TB) resolved the ENGINE POWER REDUCE problem (even though I had opened the butterfly while the positioning sensor (TBPS) was connected), and the MAF sensor problem (HIGH IDLE) was resolved by turning the wire harness connector ‘on and off’ half a dozen times until it started sending MAF g/s information to my OSB – reset the ECM again, and it was back to normal idle of about 850 rpm.

  • The problem eventually became more persistent and did not self-correct as rapidly, making driving unreliable.
  • I purchased a Scanner that connects to my smartphone through Bluetooth and was told there was a throttle body issue, requiring me to “repair throttle body component” or something along those lines.
  • ), and my toothbrush became lodged in there, so I ended up having to push it open to get the brush out of the throttle body.
  • Returning to the internet, it appears to be a regular event, but this is not the case.
  • We discovered how to reset the car’s Warning Information and discovered that the problem is now the Mass Air Flow Sensor!
  • After seeing the OSB2 was reading zero grams per second even though it was sensing a temperature (I believed it had a reading early on but wasn’t sure), I began removing the Air Filter and running it, detaching and reconnecting the MAFsensor, and then running and resetting the engine.

I had to reset the car’s diagnostic information at some point, and wahlah, it was fixed within minutes (or was it instantaneous?) It is idle at 800 revolutions per minute.

After that, it’s just a matter of putting the air filter back in; if the problem returns, I’ll buy a new WIRE HARNESS CONNECTOR to connect to the MAF sensor.

I’ve read a lot of postings this week and am grateful to everyone who took the time to share their experience; MY PROBLEM HAS BEEN SOLVED, and I want to contribute back in the hopes that my knowledge may assist you in figuring it out.

Then I went for a cruise, and it progressively started to become worse.

However, things have changed, and I am grateful that I am writing this down now; it serves as a notebook to help me keep track of my progress on this journey.

I understand that the MAFsensor should be around 4 g/s and that if the OBD2 reads 0 that the sensor connecter is not ‘connected’ but that the sensor is good (saving 120$).-Did I read somewhere that shorting the wire harness around the MAFsensor can cause high idle and throttle problems?

If I reset the EMC, the car recovers to normal idle and almost normal throttle for a short period of time after that.

I am able to change the wire connector for the MAFsensor.

GM can flash my car computer (does flashing imply reinstalling the cars programming?) before I install the new TB, but I will not be able to obtain a reimbursement for the work done! I am able to install the NEW TBw/TBPS that I have previously purchased.

Reduced Engine Power Problem Fixed on

Warning: Engine Power Has Been Reduced Unfortunately, there is more than one probable root cause for the lower engine power issue that has been seen in Chevrolet vehicles. Keep in mind that when I mention Chevy, I’m referring to both the Chevrolet and GMC trucks in this post. What’s intriguing is that, because the fault is in the drive-by-wire configuration, you could actually see other warnings appear on the driver information center screen in addition to the one about lowering power. This sort of failure will have an impact on any system in which the computer intervenes and takes over the control of the throttle position.

In this short post about the failure, we will go through some of the likely reasons behind it.

In the event that today is your fortunate day, you’ll discover a loose ground strap located between the firewall and engine block.

Reduced Engine Power System Ground Problem

Because of the loose or corroded ground strap, the best-case situation, as I mentioned in the introduction, becomes the best-case scenario. So let’s start with that subject first. This braided steel strap is responsible for connecting the engine grounds to the solid metal firewall, which is a critical function. This connection may be found just in front of the steering wheel on the engine compartment side of the vehicle. Because they are trucks, and trucks work hard, it is likely that they have worked themselves into a state of disarray.

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Road slush that contains salt can be kicked up to both sides of the ground connection.

You’ve most likely discovered the source of the problem if they relocate.

Common Throttle Actuator Problems

Assembly of the Throttle Body and Actuator Now that we’ve discussed the best-case scenario, let’s take a look at some of the other possible causes of the reduced engine power warning appearing on the instrument cluster. P1516 is a diagnostic issue code that is frequently found in vehicles when they are scanned. When the engine control module determines that the throttle actuator is providing inaccurate information, this code is generated. When the vehicle’s primary powertrain control module cannot rely on the data coming from the throttle actuator, it switches to a lower power mode for safety reasons to prevent a collision.

  • In the throttle body assembly itself, there are three independent internal components that might fail at different times.
  • P0121 is the most frequently seen set fault code for failure of the TPS part of the throttle body, and it is also the most frequently encountered set issue code overall.
  • The shaft and plate of the throttle might bind and become stuck.
  • General Motors experienced similar throttle body problem on its difficult 4.3 L V-6 Vortec engine many years ago, and it was resolved.
  • If it becomes stuck, the computer has a difficult time finding the correct place.
  • A code P0120 through P0124 might be set, indicating that there is a problem with communication with the TPS sensor.
  • Until a few years ago, this was a separate part that could be readily replaced.
  • The pieces were incorporated into the actuator assembly when they switched to a drive-by-wire technology, nevertheless, as previously stated.
  • This is not always the case.
  • When purchasing the throttle position sensor, you may purchase it separately from the full assembly, and sure, this will save you money.

However, if the TPS is replaced without first cleaning the throttle body and fixing any sticky conditions, the problem will remain, and the low power light and accompanying check engine light codes will illuminate once again, as previously stated.

Throttle Body Electrical and Wiring Problems

Harness for a Pigtail Actuator in need of replacement Befor we get any further, we need to address another issue: the electrical connections that connect the electronic control module to the throttle actuator. The information from the actuator is transferred back to the ECM, and the computer sends output commands to the positioning motor in response to the information from the actuator. All of this communication is carried out using a six-wire harness system. In order to get to the actuator connector, the harness must make an oblique turn.

  1. It is possible to test both the harness and the connection in a handful of different methods.
  2. To move the wires inside, try using two hands and an up and down motion to shift them.
  3. You may find out more about this form of electrical diagnostic by visiting this website.
  4. You may do the same wiggle test with the connector where it connects to the black plastic actuator housing by wiggle-testing the connector.
  5. However, they wouldn’t offer a new harness on Amazon if this wasn’t a problem with a significant number of vehicles at the time of writing.

Final Thoughts about Reduced Engine Power

When I notice a reduced engine power indicator, I see professionals and retail car repair shops advise that the throttle body be cleaned. This is much too often. The fact that cleaning this region is associated with the warning message makes it an easy sell. The unfortunate reality is that the chances of a cleaning truly solving the problem are the same as the chances of winning the lottery or being struck by lightning combined. In fact, the cleaning may cause more harm than benefit in several instances.

To resolve the reduced engine power message issue, there is currently no silver bullet.

The good news is that there is a 50-50 probability that it will be a less expensive alternative.

Thank Driverless Cars for This Throttle Actuator Problem

View of the Throttle Actuator Connector This brings me to my final thought on the drive-by-wire method, which is not a nice one. For almost 110 years, we increased engine speed by means of a throttle cable. This mechanical connection was completely successful. Car makers, on the other hand, realized decades ago that autonomous cars were the future and needed to devise a mechanism to manage the throttle without relying on the foot of the driver. These first generation systems were the most problematic.

Of course, that’s simply a jaded point of view from the perspective of a seasoned master mechanic.

The question is whether or not the dependability of the technology has caught up with the goal of a self-driving automobile. Because I am an Amazon Associate, I receive money when people make eligible purchases.

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What is Engine Power Reduced message on GM vehicles?

“Engine power has been reduced,” reads the notice shown on the dashboard of General Motors cars equipped with an electronic throttle body (ETB). A mechanic cable connecting the throttle plate and the accelerator pedal is not present in certain automobiles. The throttle plate is opened and closed by an electric motor located inside the throttle body, and the movement of the plate is completely controlled by the vehicle computer, which sends a signal to the motor. When the computer detects that there is a problem with the engine, it displays the message “engine power reduced” and may put the engine into “limp home” mode to conserve fuel.

What to do when Engine Power Reduced message comes on?

It all depends on the issues at hand. It’s interesting to note that the car behaves differently depending on the nature of the issue. In the case of an evident problem, such as an overheating engine, the message appears, and a coolant temperature warning light lights as well. Excessive restriction is placed on acceleration and top speed. In this instance, you must come to a complete stop and let the car to cool down. Although the message “Engine Power is Reduced,” you may not notice any drop in performance on occasion, even though the sign states so.

However, the performance of the engine may be lowered the next time you drive.

Common Causes of Engine Power Reduced

If you receive the message when the check engine light is illuminated, use an OBD scan tool to obtain the diagnostic issue codes. P0120 through P0124, P1516, and P2135 through P2140 are examples of what you could see. All of these codes have anything to do with an electronic throttle body (ETB). Depending on how much miles your car has, the interior of the throttle body may be dusty and sticky. Excessive carbon buildup can have a negative impact on idle speed, and a sticky throttle plate might result in sluggish acceleration.

  1. Consequently, if it’s unclean, clean it up with a suitable cleaner and then go through with the idle relearn operation.
  2. It is possible for a throttle position sensor (TPS) to be malfunctioning, resulting in the errors listed above.
  3. It is possible to save money by changing simply the TPS rather of the entire assembly.
  4. Keep in mind that you may still need to clean the throttle body if it is filthy and execute the idle relearn method after you have completed this operation.
  5. As a result, if the problem is with the electric motor (as well as the gears and pinions), changing the TPS will not solve the issue.
  6. The ETB can also be caused by a broken harness or cables attached to the ETB, which is a common and plausible occurrence.
  7. These connections are not particularly dependable.

Fortunately, you may purchase the replacement harness on its own as well. It is far less expensive than the TPS or ETB. However, keep in mind that you will still require the idle relearn procedure after the replacement.


Engine Power Reduced is the notification that the car computer displays to warn you when there is a problem with the engine power. At the same time, owing to contemporary car technology, the computer has complete control over and the ability to regulate performance. Although it may appear to be inconvenient, it really serves to safeguard the engine from additional harm. To avoid confusion, anytime you see the notification, respond correctly. It is possible that you will not notice a significant decrease in performance at times.

Help! Bad stuttering/rough idle/reduced engine power

It’s possible that the high pressure fuel pump in my 2009 R55 Clubman S is failing. It has been stuttering intermittently on starting for the last week. I had to restart the car four times this morning before it finally idled. It booted up and ran for a few of seconds before dying on the first three attempts. as though they were running out of gasoline During the most recent test run, it initially ran a little “choked,” then surged up to 1200 rpm before settling back down to idle, as if it had finally built up adequate fuel pressure.

  1. The HPFP, according to my indy technician, is the culprit.
  2. I’ve reached the end of my extended warranty coverage at 144k miles.
  3. I spoke with MINI about whether they would fund the repair pro rata because I had accumulated more than 120k miles.
  4. The dealer is charging $145 for the diagnostic.
  5. It appears to be a long shot.
  6. They offer two pricing structures: one for retail customers and another that is far less expensive for loyal clients.

BMW Engine Malfunction Reduced Power

In this article, you will learn about typical problems that might cause BMWenginemalfunction, as well as how to diagnose the problem on your own computer. When your car’s engine computer (DME module) identifies a malfunction, the BMWEngineMalfunction Reduced Power notice appears on the dashboard. It’s possible that the check engine light (service engine soon) may illuminate together with the BMW engine problem warning when the BMW Drive appears on your screen.

The color of the check engine light can assist you in determining how serious the problem is. The color of the check engine light can assist you in determining how serious the problem is.


On the iDrive screen, the notice “BMW Engine Malfunction” is shown. It is possible for BMW owners to have the following symptoms:

  • Engine power is reduced
  • Emissions are increased
  • Output is reduced
  • The transmission is in limp home mode (in certain situations)
  • The drivetrain is malfunctioning
  • And the engine light comes on. During acceleration, the engine message is reduced in severity.

Common Problems

These are the most typical issues that result in the BMW Engine Malfunction Reduced Power notice appearing on the dashboard. Starting with reading the trouble codes by attaching a BMW scanner to theOBD-IIport located beneath the dashboard on the driver’s side, you may discover what is causing the warning to appear.


Valvetronic is a feature found on the majority of BMW engines. It allows you to vary the amount of intake valve lift, hence removing the necessity for a throttle plate. Despite the fact that this is a complicated system, it is quite resilient. Depending on how well it performs, you may experience poor throttle response and power. Electric motors and eccentric shaft position sensors are two of the most common failure areas. 2A61, 2A63, 2A67, 2A6F, and 2A70 are the codes to look for.


Vanos is operated by actuators that are driven by oil. It is an easy-to-use and dependable method to use. It will fail in the vast majority of situations if there is an accumulation of oil sludge within the Vanos solenoids. This is due to the fact that oil change intervals are excessively long. Fortunately, replacing a malfunctioning Vanos solenoid is a simple and inexpensive procedure. Additionally, you will hear engine noise, such as tapping or banging noises, in addition to the “BMW engine problem decreased power” statement (VANOS area).

2A82 and 2A87 are the codes to look for.

Oxygen SensorSensor

Optimal engine performance is achieved by the utilization of signals from upstream oxygen sensors by BMW engine control. Excessive fuel or oil use might cause upstream oxygen sensors to get clogged. Furthermore, faulty wiring or a faulty connection are both probable scenarios. Any of these factors will have an impact on engine performance, and a yellow 1/2 “check engine light” will illuminate on the dashboard of your vehicle. 2C9C, 2C9C, or P0171 to P0174 are all valid codes.

Ignition Coils

There are a variety of reasons why ignition coils might fail. It will result in misfire, which will cause the engine to shake and judder as the vehicle is accelerated. Misfireis extremely harmful to yourcatalytic converter, so avoid driving your BMW if it has a misfire in it. Ignition coils are inexpensive and simple to change, so it’s a good idea to keep one on hand just in case. A faulty connection between the ignition coil and the BMW engine might result in the appearance of the BMW engine malfunction yellow light.

Timing Chain

‘Check engine light’ issues that are connected to the timing chain might cause the check engine light to come on. Although timing chains are intended to be used for a lifetime, they can get exclusively stretched as a result of wear and use. Tensioners and plastic guides might both fail at the same time. The engine will rattle, and the yellow 1/2 ‘check engine light will illuminate, as well as Vano’s reengine light and Vano’s associated codes, if the timing has jumped two or three teeth.

It is possible to have a larger timing jump when you have a Red 1/2 check engine light on and a larger engine light on. In any event, please switch off the engine immediately and do not start it again after it has been turned off.


A low-quality battery might result in the BMW Engine Malfunction Reduced Power notice appearing on the iDrive display. BMW automobiles are sensitive to voltage fluctuations, and if the battery is old, it may not be able to maintain a sufficient charge. If your battery is more than seven years old, it is necessary to replace it in order to avoid more electrical problems. A badalternatorregulator can also induce symptoms that are similar to those described above.

See also:  Replacement Ford oil filter cap? (Solution)

High-PressureFuel Pump(HPFP)

The engines in newer BMW automobiles, beginning with the E90 335i, are equipped with high-pressure fuel injection. This is a fragile mechanism that can be harmed by using low-quality gasoline or ethanol. High-pressure fuel pumps and injectors are the most common points of failure in this system. Symptoms include a hard start with a long cranking period, a rough idle, and a yellow 1/2 ‘check engine light’ on the instrument cluster. In the majority of situations, power output and acceleration are significantly reduced.

29DC, 29E2 are the codes for 2FBA and 2FBF, respectively.


Your turbocharged BMW may be experiencing boost leaks, resulting in less power and slow acceleration during acceleration. Even something as basic as a faulty vacuum line might result in this situation. Boost solenoids, which control the operation of the turbochargers, might fail. Check the charge piping that links the turbocharger to the intercooler and intake manifold, as well as the turbo itself. These are rubber hoses that have the potential to rupture or come loose. The last thing to consider is if your wastegate is jammed open or whether you have a leaky blow-off valve.

How to diagnose BMW Engine Malfunction Reduced Power

BMW Engine Malfunction can only be diagnosed with a BMW Scanner, which reads trouble codes particular to the manufacturer of the BMW engine. Pay close attention to any problem codes generated by the DME module, and run a comprehensive system scan as well.

Frequently Asked Questions

My BMW is equipped with a large yellow check light that indicates “Engine failure!” Power has been reduced. What do you recommend I do? If you see this notice, it indicates that your engine is experiencing a major problem. Although it is still safe to drive to your destination, it is recommended that you change your driving style to a “moderate.” Take a few minutes to pull over in a safe location and examine under the hood of your vehicle. Correct the situation as quickly as feasible. This notice can appear on an E60, E70, E90, E92, E65, or F10, among other things.

Because the engine is not running at peak performance, it is not recommended that you place it under a heavy load.

Drive with caution.

Unusual exhaust smoke, engine judder, or excessive engine temperatures are all indications that something is wrong.

Some OBD2 scanners are only capable of reading the powertrain codes that are required by law (Pxxxx).

Because BMWs are more complicated than other automobiles, they have a large number of manufacturer-specific codes. An engine scan instrument that is capable of interpreting this type of signal is required for accurate engine diagnosis.

Reduced engine Power 8.1L Workhorse

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08-12-2020, 10:41 PM 1
Junior MemberJoin Date: Jul 2020Location: Kelso, WAPosts: 26 Reduced engine Power 8.1L Workhorse

2003 8.1L Workhorse chassis.Under a Southwind. I am having the same problem. I just let it idle today and all was fine. The problem was gone. Then revved it up to 3000 for awhile turned it off and it barely turned over. used Aux to get the engine going and the REDUCED ENGINE POWER AND CHECK ENGINE LIGHT CAME ON. Engine barely ran and not over 1800 RPM.I came in and researched the internet and then went out disconnected the battery and tried to start it. Got it to stated using the Aux Battery and it ran fine now that it was cold. Yet check engine light still on. I had the throttle body worked on a few years ago and still having issue. I find that when turning over to start it starts out slow and then will start. The engine battery is less that one year old and I took it back and had it bench tested. Not sure what to do.House battery’s are new also. Not sure where to go first. I can’t see how to even get to the throttle body.Any suggestions. I bought new and only have 30,000 on the engine. Now retired and afraid to go anywhere. Any suggestions would be well accepted. Joe Abram

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08-12-2020, 10:55 PM 2
Senior MemberJoin Date: Jun 2016Location: SW LouisianaPosts: 6,890 Get an OBDII code scanner and see what codes set the check engine light, you can buy a basic stand alone unit for under $25 on amazon, or a smart phone dongle type for under $15_2002 Safari Trek 2830 on P32 Chassis with 8.1L w/ 400 watts solar 420Ah LiFePo42017 Jeep Cherokee Overland2007 Toyota Yaris TOADs with Even Brake,Demco Commander tow bar and Blue Ox / Roadmaster base plates
08-13-2020, 09:42 AM 3
Junior MemberJoin Date: Jul 2020Location: Kelso, WAPosts: 26 Thanks I ordered and will receive Friday.
08-13-2020, 09:57 AM 4
Moderator EmeritusJoin Date: Jan 2000Location: Silver Springs, FL. USAPosts: 24,729 Barely turned over sounds like a chassis battery or ground cable problem, but rarely could that cause check engine.However, if the ECM (engine computer) has lost power or connection to its sensors, it could well throw error codes and reduce power._Gary BrinckFormer owner of 2004 American Tradition and several other RVsHome is in the Ocala Nat’l Forest near Ocala, FL
08-13-2020, 10:30 AM 5
Senior MemberJoin Date: Mar 2015Posts: 102 Seen this problem a few times.Clean and tighten your battery terminals
08-13-2020, 10:41 AM 6
Senior MemberJoin Date: Sep 2010Location: Groves,TXPosts: 521 I had that happen, and read code said throttle position sensor in throttle body_2004 Allegro Bay 37′ W/8.1
08-13-2020, 11:23 AM 7
Senior MemberJoin Date: Mar 2015Posts: 102 Quote:Originally Posted byfletch460I had that happen, and read code said throttle position sensor in throttle bodyYep that’s what code I had too. Replaced sensor before I figured it iout. My nephew and BIL both have had same problem. Each time was battery terminalsNot saying sensor wasn’t your problem but on ours it was a false code
08-14-2020, 12:11 AM 8
Junior MemberJoin Date: Jul 2020Location: Kelso, WAPosts: 26 Thank guys. The Battery shop says battery is fine. going to bring my starter in tomorrow just to be safe and they are going to bench test it.It could be somehow drawing amps or volts and screwing up the battery. cuz the starter does not want to turn over very fast and some times not at all unless I use the aux Battery switch or jump it. I am still getting a code device tomorrow afternoon. I wish I was a better mechanic. But do appreciate all your advice. Did go and get some MAF cleaner today and sprayed the MAF sensor.
08-17-2020, 08:45 PM 9
Senior MemberJoin Date: Aug 2019Location: A beach or race track near you.Posts: 519 Quote:Originally Posted by65MalibuThank guys. The Battery shop says battery is fine. going to bring my starter in tomorrow just to be safe and they are going to bench test it.It could be somehow drawing amps or volts and screwing up the battery. cuz the starter does not want to turn over very fast and some times not at all unless I use the aux Battery switch or jump it. I am still getting a code device tomorrow afternoon. I wish I was a better mechanic. But do appreciate all your advice. Did go and get some MAF cleaner today and sprayed the MAF sensor.I own am 01 GMC pickup with 8.1 and Allison trans (same combo as your MH), I have fought this same situation for several years. Truck will start and run rough, have a dead miss or only run on a few cylinders or at reduced power. Have little to no throttle response. Check engine light will come on and flash repeatedly.I can pull over normally, cut truck off and re-start and it will run fine. Sometimes it take one or two attempts but it will work.Finally a mechanic friend suggested installing a battery tender. My truck does sit a lot, sometimes two or three weeks at a time. So I installed a new battery and a battery tender, problem solved.I got lazy and stopped hooking up the battery tender and the problem returned almost instantly.Mechanic friend’s theory is the alternator is pulling so hard at start up, it is causing low voltage at the computer.? I don’t know, but it seems to fix the problem after several years of this issue.I like you had become afraid to take the truck out on the road (I used it to pull my race car before I bought a DP) for fear of break down. Now, as long as I hook the battery tender up when I park it, it’s ready to go when I am.Good luck.
08-17-2020, 10:31 PM 10
Senior MemberMonaco Owners Club Workhorse Chassis OwnerJoin Date: Aug 2002Location: Clovis, CA, USAPosts: 11,313 said the Check Engine Light will come on and flash repeatedly.Did you ever use a code reader on it?The manual says with a flashing CEL you should pull over and call a tow truck._2004 Monaco La Palma 36DBD, W22, 8.1, 7.1 MPG2000 LEXUS RX300 FWD 22MPG 4020 LBSIt’s so weird being the same age as old people.
08-18-2020, 08:17 AM 11
Senior MemberJoin Date: Aug 2019Location: A beach or race track near you.Posts: 519 Quote:Originally Posted byArch said the Check Engine Light will come on and flash repeatedly.Did you ever use a code reader on it?The manual says with a flashing CEL you should pull over and call a tow truck.One of the last incidents, the transmission acted up. It finally set a code that referred to low voltage. That is what lead us to the battery tender repair.My friend that was helping me is a mobile mechanic, and has a Snap-on Solas scanner and was reading codes for me.Prior to the transmission deal, it NEVER set a code. It would flash and generally go crazy, but once I cut it off and re-started the truck, it was like it never happened. I would drive directly to his shop and attempt to scan the computer, but would get nothing.I did replace the battery at the same time I added the battery tender, (it was 8 years old) but I had been dealing with this for a very long time. Battery was just coincidence.Computers HATE low voltage and bad grounds.I think the manual tells you to call a tow truck because If the CEL is flashing, the engine is running so bad, it will clog the converter and possibly cause a fire. My truck would run that bad. It would barely pull it self along. I would have to stop in the road in front of my house, shift into park/nuetral, cut it off, re-start and drive off. Worked almost every time on the first try, VERY aggravating!
08-18-2020, 11:15 AM 12
Junior MemberJoin Date: Jul 2020Location: Kelso, WAPosts: 26 I replaced the starter and CEL disappeared and engine turns over immediately and the REDUCED ENGINE POWER message gone. Short road trip went fine. Put code meter on it and no codes.
08-18-2020, 03:11 PM 13
Senior MemberMonaco Owners Club Workhorse Chassis OwnerJoin Date: Aug 2002Location: Clovis, CA, USAPosts: 11,313 Let’s hope all is well!_2004 Monaco La Palma 36DBD, W22, 8.1, 7.1 MPG2000 LEXUS RX300 FWD 22MPG 4020 LBSIt’s so weird being the same age as old people.
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