Reduced Engine Power Warning Light

After scanning your vehicle, it should be fairly easy, to pin point exactly where the issue is coming from.


Because, any one or combination, can cause, reduced engine power.

1- Faulty Ground Connections ( Very Common )

For instance, when the system detects a serious problem with:

  • Sensors
  • Circuits
  • Engine controls
  • Transmission components
  • Emission controls
  • Brake controls

The First Three Things You Need To Check Are:

A faulty ground connection will cause, voltage and current to drop, leading to all kinds of driveability issues. So, check the engine grounds in your vehicle, with the use of a digital multimeter. This will make it easier, to detect loose, corroded or damaged connections. Consequently, affecting sensors, actuators or system circuits.

2- Diagnostic Trouble Codes (DTC)s



Faulty engine grounds, are sometimes to blame, for many apparently faulty parts or wires. So, one of the first checks you want to make, is the condition of engine grounds, including battery connections.

So, just remember the basics. Is a wire loose? Did a vacuum line fall off ? Do not look for, a complicated solution, to a simple problem. Finally, it is common to have a problem in one area, that impacts three or four others.

So, the “reduced engine power” warning light on your dash, means that your vehicle’s performance has been reduced. Above all, to avoid damaging your engine.

Reduced Engine Power Warning Light - What To Do And Why?
Reduced Engine Power Warning Light – What To Do And Why?

Reduced Engine Power, can have many different names. All depending on the year, make and model of your vehicle.

So, whether its, reduced engine power, limp mode, fail safe mode or limp home mode, they are all the same.

However, reduced engine power, is the most common name, for late model vehicles.

Your vehicle can have a wide array of control modules that monitor values, from different sensors and actuators. So, as long as these values are what it would normally expect, then it would perform normally.

Sensors - Monitor And Control, Various Engine Parameters
Sensors – Monitor And Control, Various Engine Parameters

So, the first thing to check, is the Diagnostic Trouble Codes (DTC)s. You can use a scan tool to download trouble codes, stored in the Electronic Control Module (ECM) of your vehicle.

Reading Diagnostic Trouble Codes (DTC)s
Reading Diagnostic Trouble Codes (DTC)s

Many of the causes of reduced engine power, are issues that will need to be addressed, immediately. However, this should not be a cause for panic. Consequently, most of these issues, can be repaired with a little research and some basic know how.

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.

However, if the control module all of a sudden receives, unbalanced signals, from one of the sensors. And, is out of the normal range. Then, the computer is programmed, to take some type of action. (not within the parameters expected from this sensor).

Just like when your home computer, when it goes into safe mode, limiting functions that may cause further damage.  When your vehicle goes into this mode, it operates with limited functionality and speed. Consequently, this mode is intended to help the driver, get to a service shop safely.

As a result, you may see any one of the following:

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

Most of the time, these codes will steer you in the right direction, to see where the faults are.

3- Check For Technical Service Bulletins (TSB)s And Software Updates For, Reduced Engine Power

So, depending on how far out of range this signal is, will decide what action will be taken. It may turn on something as simple as, a Check Engine Light (CEL). And, in some cases, may save Diagnostic Trouble Codes (DTC)s, which will indicate where the fault occurred.

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.

Reduced Engine Power Warning Light
Reduced Engine Power Warning Light

Hence, a (TSB) is a communication, to update automaker publications, describe parts updates, inform of potential defects or failures. And, can also relay any enhanced or new service procedures. A (TSB) is not a recall, but rather an informative document, alerting the public to a potential problem.

Common Causes, For A Reduced Engine Power Warning Include:

  • A loose wire, harness, or clamp
  • Oxygen (O2) sensors are failing
  • Throttle Position Sensor (TPS) is faulty
  • A throttle body issue
  • Mass airflow (MAF) sensor is faulty
  • The vehicle’s (ECU) is faulty
  • Fuel pump issues
  • A clogged catalytic converter
  • Fault in the transmission
  • Accelerator pedal position sensor
  • Bad ground

Actually, there are more issues than you think on this subject. Sometimes people jump into a repair, without reading all of the appropriate service information. So, one way to stay informed is, through the use of Technical Service Bulletins (TSB)s. Furthermore, a (TSB) provides information on, potential vehicle related issues.

Technical Service Bulletins (TSB)s
Technical Service Bulletins (TSB)s