What is limp mode in a car and why is it important?

Most modern cars nowadays already come with limp mode, which is an essential feature that is automatically activated when the electrical component or mechanical operation of your vehicle is malfunctioning. While not all people are familiar with this, there are specific symptoms and causes when your car engages in limp mode. Before we get onto those details, let’s first understand this feature and why should it be considered essential for any vehicle?

What is limp mode?

For better understanding, limp mode or also know as ‘limp home mode’, is a security feature of a car that automatically activates when it detects a fault with the engine or transmission. What it does is it will deactivate or reduce the performance of certain features of a vehicle such as the air conditioning system, as well as the power that the engine produces. This ensures that the fault detected by the system doesn’t cause anything serious and helps the car to limp home. 

Why is limp mode important?

Limp mode serves as a self-preservation feature of your car as it protects it from any possible shutdown or from any dangerous situation that could happen due to the mechanical fault detected. By turning off all unnecessary features such as your radio and air conditioning system, the vehicle is then able to safely limp back home.

What are the symptoms of limp mode?
  • Limited speed and RPM - When the car is engaged in limp mode, the system will be responsible for limiting the amount of power on your engine and transmission. It also limits the RPM as well, therefore, reducing the car’s speed from about 48 km/h to 72 km/h. That said, this security feature makes it dangerous for a car to drive on the highway given that it is unable to reach the minimum speed of 80 km/h.
  • Poor performance - As mentioned, the system will limit the speed and RPM of your vehicle. In conjunction with this, your car’s acceleration will be very slow, plus, you might even feel your engine shivering or shaking while trying to accelerate. The gearbox, on the other hand, could automatically downshift. So if you’re unable to shift above third gear or you can’t even shift your gears at all, then it is a sign that your car is in limp mode.
  • Check engine light turns on - Your car’s check engine light could flash repeatedly, though it does differ depending on the type of failure your vehicle has. There is also a chance that your car will overheat, if that happens, give it a rest before driving it again in order to prevent any further damage.
What are the common causes of limp mode
  • Sensor malfunction - There are a few sensors that control the engine and transmission of the car. Now, if one of the sensors is sending incorrect signals to the computer, then the car will engage in limp mode.
  • Damaged wiring - Another possible cause for your car to engage in limp mode is damaged wiring. The following cables deteriorate given the heat, debris, or acid leaking onto them, therefore, causing corrosion and wear over time. Technically speaking, the damaged wire is unable to send the right electric signal to the computer, therefore causing it to think that a certain part of a car has failed.
  • Low fluid level - Last on the list is having low fluid levels. The transmission fluid and oil are very important in an engine as they lubricate the different parts of your car which then reduces friction and allows better mechanical operation. That said, take note that low fluid levels can activate the limp mode, that’s why it’s important to have it checked and replaced when needed.
  • Failed clutch and transmission - Limp mode is also activated when the clutch of your vehicle is damaged or faulty. Moreover, a broken transmission linkage can also activate limp mode. Remember, the linkage is in charge of shifting gears, so having it broken is a huge problem to the vehicle’s mechanical operation.

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