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What is Limp Mode And How To Fix It?
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What is Limp Mode and how to fix it?

 

 

You are driving on the highway and suddenly the transmission is shifting down to 3rd gear and put an rpm limit at max 2500 rpm. You feel that your engine seems very slow. 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’m working as a diagnostic technician. I have seen the most faults that could occur in all vehicles and know how to fix and diagnose it the fastest and cheapest way. In this article, I will teach you everything about limp home mode, What it is and why it does happen.

What is Limp mode?

Limp mode is a state when you got limited functions from your engine control unit and transmission control unit.

Some common characteristics could be:limp mode

  • Reduced Engine Power
  • RPM Limit Lowered
  • Transmission is “stuck” in a gear
  • Check Engine light/Half engine light is flashing

 

It is depending a lot on what brand model and engine you have. There are many types of limp modes depending on how the manufacturer designed it.


What causes Limp mode?

The engine is set into limp mode when the car has detected a fault with the engine or transmission. It’s a security function. The engine control unit is reducing the power and limit a lot of functions so you could drive your car to the closest workshop without destroying your engine.

The most common causes arep0420 code fix

  • Electrical problems
  • Turbo boost problem
  • Electrical Transmission fault
  • Electric throttle valve problem
  • Sensor faults

 

That is only the most common causes and you should not use that list to start replacing parts without doing some real troubleshooting. When the engine is getting wrong values from a sensor is a normal case. What the engine control unit is doing with limp mode is using some calculated values out of other parameters which it think would be correct. In that case, the engine control unit will limit the functions because it’s not sure that it uses the real values.


limp mode

How do I fix the Limp mode?

 

To fix the limp mode, the first stage you have to do is to read the trouble code memory. When the car is going into limp mode it will have a stored trouble code inside either the engine control unit or the transmission control unit. You can either read the trouble codes from home with a cheaper DTC code tool or you can drive to a workshop which probably will have better diagnostic tools to make a better troubleshooting.

If you want to read the trouble codes at home I would recommend this tool: FOXWELL NT301 Car Obd2 Code Scanner. I work well to read and erase the DTC memory of the most vehicles in the market. With this tool, you can read your trouble code memory at home and then use Google or Bing to find information about the code or check out one of our other articles for a more detailed guide: How to troubleshoot your car in 5 steps. Also, see Generic DTC code list

But I still recommend you to go to a workshop with better diagnostic tools to make a correct troubleshooting.

When you have detected the fault and fixed if you have to go out and try your car under the same conditions as before. Try to remember at which speed, gear and load it happened. Try to induce the faults again to be 100% sure that the problem is fixed.

 

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.

 

If you have any questions that still is unclear you can either Comment below or ask a question at our site and I will help you out.
You can also give us feedback if you want us to change anything in this article.

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About Ask A Mechanic AdminDiagnostic Technician

Hello. I live in sweden and work as an Automotive Diagnostic Technician. Worked with the most brands in the most advanced fault diagnostics. Im here to answer all your automotive questions. If you have any private questions you could send me a PM and I'll answer them as soon as possible!

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