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Limp Mode – Meaning, Causes & Solutions

Posted by on January 15, 2018 | 0 Comments

limp modeYou are driving on the highway and suddenly the transmission is shifting down to the 3rd gear and you suddenly have an RPM Limit on 2500 rpms. You feel that your engine acceleration is lowered a lot and your check engine light is flashing on the dashboard. That’s exactly what could happen when the car is going into Limp Mode. But why does that happen and how expensive will it be to fix? You may think.

I work as a car technician, I have seen the most possible problems in different vehicles and I know how to repair and diagnose them the fastest and cheapest way. In this article, I will teach you everything you have to know about limp home mode, What it is and why it does happen.

 

In this article:

 

ProblemSymptomsCausesSolution
Limp ModeRev Limit 2500-4000 RPM

Low Performance

Under-boost

Transmission shifting max 3rd gear

Check Engine Light

Restricted Functions
Engine boost control, Overboost/Underboost

Faulty engine sensors

Faulty engine components

Engine wiring issues

Transmission issues

Transmission wiring issues

Brake system wiring issues
Read the trouble code memory with an OBD2 scanner.


This will help you to find the problem the cheapest and fastest way.

 

What is Limp mode?

Limp mode is a security function for your car’s engine and transmission. When the engine or transmission control unit has recognized a serious faulty value from the engine or transmission, the car will go into limp mode. The limp mode does often reduce the power and limit the RPM of the engine so you can drive the closest way to a workshop without damaging the engine.

For an example: Your engine control unit is detecting that your turbo boost is 2.0 bar when the maximum boost pressure should be 1.3 bar. Overboost could blow your engine really fast and because many drivers do not care enough about the engine light, it does put your engine into limp mode and shut off the turbo boost completely and put a max RPM limit to 3000 RPM’s so you won’t blow your engine.

Limp mode is created to get you to the workshop in the safest way without damaging anything on your engine on the way. Different car manufacturers design different kinds of limp modes to save your engine. The common characteristics are different depending on the problem with your engine/transmission and depending on which car and engine you have. But there are some characteristics that are used in the most causes for limp mode.

Some common characteristics of limp mode could be:

  • Reduced Engine Power / Turbo boost shut off completely
  • RPM Limit Lowered
  • Your Automatic Transmission is “stuck” in a gear/limited to max 3rd gear
  • Check Engine light/Half engine light/EPC(Volkswagen) is flashing

 

Possible causes of limp mode

  • Engine boost control, Overboost/Underboost
  • Faulty engine sensors
  • Faulty engine components
  • Engine wiring issues
  • Transmission issues
  • Transmission wiring issues
  • Brake system wiring issues

As you see I do only mention the issues in general. That is because I do not want you to replace parts that are not faulty and limp mode could have a lot of different causes. Read the trouble code memory and find a fault before you are replacing any parts!

 

 

What causes Limp mode?

ancel obd2 scanner tool
When the engine control module, transmission control module or brake control unit(ABS) finds a fault in the engine, transmission or brake system it will store a trouble code in your DTC memory.

If the control units are deciding that the problem is dangerous for the engine or transmission, it will put the car into limp mode. So the cause of limp mode can be a lot of different things.

The best way to find the cause of the limp mode is to always read out the trouble code memory first with an OBD2 scanner.

You maybe do a little research on the internet and you will get a lot of tips on what could cause the limp mode. They are telling you that they have the same characteristics of their vehicle 5 years ago and “I replaced this part and it fixed my problem”.

The problem with the limp mode is that you are getting the same characteristics with a lot of different faults. That’s why you should never listen to anyone that had the same problem before. You will only end up wasting your money on parts that do not have a fault on them.

It is really easy to read the DTC memory and find out the real solution to why your car has gotten into limp mode. You could either drive your car to a friend or a mechanic to get help to read your DTC memory, it will probably not cost a lot of money and you will get a real answer to your problem.

 

Where can I get an OBD2 scanner to solve my Limp mode?

If you want, you could also buy an OBD2 scanner to read your trouble codes at home by yourself. They do often not cost a lot and it could be a really good investment instead of taking it to your mechanic all the time and you will save the money fast. If you want to check out some different OBD2 scanners you can check our OBD2 scanner review where we have listed the best OBD2 scanners on the market.

If you got a lot of trouble codes stored in your memory and you do not know which to fix first, you could save and erase them and take it for a drive to see if the problem is coming back or not. If you are very lucky it was just a coincidence and your car may work as it should. But in the most cases, the trouble code will come back and you have to repair anything to get it away.

When you found out which error code that is causing the limp mode. You should search for some information about the code and not just replace the part that it is telling you is faulty. It does not happen to be a broken part it could be a wiring issue or something else. The OBD2 scanners in our review do have an inbuilt trouble code library where it will show you the causes and solution of different trouble codes. If you have a cheaper OBD2 scanner you could search the internet, ask us a question at our homepage or check out our trouble code list

 

What to do if limp mode occurs on the road

You should always try to avoid to drive with the limp mode on. Try to make a stop as fast as possible to check for any leakage, smoke or noise from the engine or transmission. If everything seems okay you could either drive to the closest workshop or get it towed if you feel uncomfortable. If it’s not possible, drive the shortest way to your home and fix it there or get it towed to a workshop.

Tow your car to the workshop or home is always the safest move.

 

FAQ about limp mode

My limp mode is only occurring sometimes and it is gone after an engine restart?

Limp mode is often disappeared after a restart of your vehicle. At the start of your engine, the engine control unit will check all the sensors if they are OK. If the status is Ok, the control unit will allow you to drive your car as normal. The problem is maybe not occurring at idle and that is why it will remove the limp mode automatically for you. Then when the control unit detects the fault again it will put your car into limp mode again.

My Limp mode occurs when hard accelerating and to occurring when driving normal?

If the problem only occurs when you are doing hard accelerating, there is most likely a problem with your boost control system. If the vehicle detects an overboost/underboost pressure it will be put into limp mode. If you are getting into limp mode at a lower speed or at idle also, you are most likely not having a boost problem. But you should always check your DTC memory before doing any repairs or troubleshooting.

Is it dangerous to drive with limp mode on?

Yes, the limp mode is set because of a reason. If you notice that your car has gotten into limp mode you should fix it as soon as possible. The limp mode is designed so you can drive the closest way to a workshop to get the problem fixed. Do not drive around with the engine light ON. Even if you know the problem and it’s not a fault that will cause any damage, it can hurt your engine and you will not notice if you get any real trouble with your engine.

I have replaced the damaged part, will the engine light and limp mode go away by itself?

Yes, in the most cases. The trouble code system is working in cycles. Each time you start your vehicle and it gets hot and it has tested all the sensors, it is registered as one fully functional cycle. Depending on the car model, the engine light will be reset after a fixed number of cycles. If it has detected that the fault has not occurred within 10-20 cycles it will see the problem as repaired.

But the easiest way and best way is of course to reset the engine light and trouble codes with an OBD2 scanner. With these tools, you could always check all the parameters in the engine to see if they are okay if you have some knowledge.

 

 

Summary

  • Don’t panic when the limp mode occurs. It’s designed to make your engine survive to make sure that you can drive to the workshop to repair the problem.
  • Limp mode is often caused by an electrical problem with the engine or transmission
  • Limp mode is a security state
  • Make sure that you go to a workshop or try to fix it yourself as soon as possible. It’s not good to drive around with limp mode
  • You can buy an obd2 scanner to check the cause of the limp mode yourself at home.
  • Do not just replace parts on your vehicle without reading the trouble code memory first.

If you have any more questions about the limp mode or want to tell us your store about it, you can comment down below here and let us know. If you have any other car questions you are welcome to read our other articles on our blog or ask us for free at our homepage. We will help you out as soon as possible.

Good luck with your troubleshooting and I hope that I will see you in the next article also!

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