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

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

Reduced engine power, can have many different names; 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 all have the same goal.

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

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

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.

Engine Power Is Reduced
Engine Power Is Reduced

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

So, depending on how far out of range this signal is, dictates what action will be taken. It may turn on something as simple as, a check engine light (CEL). But, 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 Mode Shown On Dashboard
Reduced Engine Power Mode Shown On Dashboard

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

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

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.

Automotive Sensors
Automotive Sensors

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:

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

Faulty Ground Connections ( Very Common )

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.

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.

Diagnostic Trouble Codes (DTC)s

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

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

Copy Of A Technical Service Bulletin (TSB)
Copy Of A Technical Service Bulletin (TSB)

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.

Hence, a (TSB) is a communication, to update automaker publications; describe parts updates, inform of potential defects or failures; or relay 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:

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

Reading Engine Trouble Codes
Reading Engine Trouble Codes


Many of the causes of reduced engine power, are issues that will need to be addressed, immediately. However, this shouldn’t 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.

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.

Thank You !