When your car turns to “limp mode”, what does this mean?

In this article, we’ll discuss the limp mode setting of vehicles – when does it come on, what happens when in this mode, and what do after it happens.

Limp mode symbol
Limp mode symbol

What does “limp mode” mean?

Limp mode or limp home mode is a safety feature of modern vehicles that triggers when the car’s computer detects a fault in the engine or transmission. It is designed to protect your vehicle from further damage by turning on the check engine light, automatic slow down, and shutting down certain functions of the vehicle (i.e. AC, radio).

Your car in limp mode is basically turning into “survival” mode. It is now intelligently focusing all remaining power and resources into allowing you to move the vehicle into a safer spot – ideally in your own garage or a car service centre. 

Is your car in limp mode?

You may experience any, or a combination, of the following events when a car goes into limp mode:

1. Check engine light is on

This could mean a multitude of things, from a loose gas cap to a defective catalytic converter. In relation to limp mode, a faulty sensor, broken wiring, or a damaged component can trigger the check engine light. 

Check engine light
Check engine light

You may need an OBD2 scanner to obtain and read the fault codes to pinpoint the problem. Remember this, though, when the check engine light flashes – NEVER ignore it!

2. Low engine power and performance

When your car experiences poor performance, there is sure to be a problem in the vehicle. One of the most common causes of this symptom is a fault in the boost-control system of the car. 

low engine performance
Low engine performance

If you have a boost leak or an over boost has just happened, the car will slow down acceleration, and you will not get the normal power from the engine. You may also feel your car “shivering” as you try to fire the engine again.  

3. Reduced speed and limited RPM

In limp mode, the car’s computer will slow you down to a maximum speed of 48 to 72 KPH, and limit your revolutions to less than 3,000 RPM. It will also automatically downshift you and will not allow you to shift above third gear. 

Car dashboard
Car dashboard

These conditions are part of this safety feature and protect you and your vehicle from further harm.  

What can trigger limp mode?

When your car goes into limp mode, you can consider any of these reasons for it:

1. Malfunctioning engine parts

When an engine component such as the transmission system or engine boost control suffers a malfunction, your car’s computer signals the entire system to go into limp mode to protect the rest of the vehicle. 

The same goes for the ignition system (i.e. spark plugs and ignition coils), fuel injection, and brakes. If any of these components break down, you will experience the symptoms we mentioned above.

Car engine
Car engine

2. Faulty sensors

A faulty sensor may send false data (or may not send any data at all) to the car’s computer, thus triggering limp mode. The common culprits here are the MAF (mass air flow), MAP (manifold absolute pressure), TPS (throttle position sensor), boost pressure sensor, oxygen sensor, and the vehicle’s speed sensors.

Even before going into limp mode, problems with starting the vehicle, acceleration, power, and fuel economy can mean that one of your sensors may have gone bad. Also, look out for rough idling and sudden stalls. This may mean that something is wrong with your sensors.  

Mass airflow sensor
Mass airflow sensor

3. Lack of car fluids

Regularly check your car fluids (i.e. brake, clutch, power steering, transmission), as well as engine oil and car coolant, if you want to prevent your vehicle from suddenly going into limp mode. 

Low fluid levels reduce lubrication and protection of specific vehicle parts. And once you prolong refilling these car fluids, it may cause further damage to the entire engine. 

Engine Oil
Engine Oil

4. Damaged Wiring

Wires around the engine deteriorate over time due to the harsh environment they are exposed to. Heat, acid, and foreign debris contribute to the wear of the vehicle wiring system. 

This causes failure in sending critical signals from engine components to the car’s computer, and thus eventually triggering limp mode.

Engine wiring
Engine Wiring

How to reset and clear limp mode

Considering the complications that cause a car to turn into limp mode, to clear and reset it can be quite simple. There are three (3) common ways on how to bypass limp mode:

Car in limp mode
Car in limp mode

1. Clear the check engine light

Use a reliable OBD2 scan tool to clear fault codes and reset limp mode. Just plug into your OBD2 port and search for the correct function.

2. Shut down the engine 

Another way to clear limp mode is to simply shut down your vehicle, wait for about five minutes, and turn on the engine again. You can also shut down longer and use this time to check engine components for damage or any malfunction.

3. Refill the car fluids

As we’ve said earlier, low fluid levels can trigger limp mode. A quick inspection will reveal if, for example, your engine oil or transmission fluid is at a critical level. Refill them immediately, and do the proper reset. 

Our Final Word

If your vehicle switches to limp mode, it is telling you that something is wrong with the vehicle and that you need to take it to the mechanic or bring it home ASAP for the fault to be fixed (thus it’s called limp HOME mode)!

If you can’t get professional help yet, you can first diagnose the problem using an OBD2 scan tool.

Resetting a car in limp mode

Nevertheless, DO NOT IGNORE if your vehicle goes into limp mode. Whether it was caused by a minor or major problem, it should be treated as a serious situation that needs immediate attention.

In the same vein, DO NOT PANIC if ever you experience limp mode. As your car slows down, pull over to the side of the road. Assess the situation: if you can still drive (slowly) to your home or the auto repair shop, well and good; if not, call your mechanic if they can tow the vehicle or if he or she can service your car there.

As with any situation on the road, it is important to keep your wits and seek professional advice or use a scan tool yourself to access the situation as small issues can lead to large expensive engine damage.