limp mode

Limp Mode: What It Is And All You Need to Know

Have you ever driven your car and then suddenly you’re not getting any power? And then your check engine light suddenly turns on? That means your car is in limp mode. A check engine light denotes that there’s something wrong with your car’s powertrain. It could be the engine, the gearbox, or the exhaust system. If this happened to you recently, don’t worry. We’ll discuss all about the limp mode in this post, from what it is, why it happens, and how to fix your car.

What Is Limp Mode?

Car Dies While Driving

Limp mode, or sometimes called limp home mode and fail-safe mode, is basically a self-preservation mode your car has. This means your car has a serious issue and continuing to drive it can cause severe damage. The issue most commonly stems from its transmission.

It engages limp mode to limit the engine power output and transmission to prevent such damage. You will notice that your car can only engage one gear, maybe two in some cars. And it will limit the speed to just around 30 – 45mph.

The purpose of limp mode is so that you can continue driving to get home or your destination while preventing any further damage while doing so. In most cases, your car will also turn off accessories like the air-conditioning and radio to preserve energy to run the car. But what exactly causes limp mode?

What Causes Limp Mode?

As mentioned, the issue most likely stems from your transmission unit. But other things may also cause your car to engage limp mode, here are the possible causes:

Low Transmission Fluid

The transmission is a collection of gears that transmits power from the engine to the wheels more efficiently. Since the gears inside experience a lot of friction, it needs a lubricant to reduce friction and heat. This keeps your transmission running smoothly and prolongs its lifespan.

The transmission fluid typically needs to be replaced every 30,000 to 50,000 miles. If the fluid is old, it won’t be as effective in lubricating the transmission. Additionally, transmission fluid can leak if the gasket or pan is worn out or damaged.

If the transmission doesn’t have enough fluid, it can lose pressure which prevents it from working properly. Also, not enough fluid means the transmission won’t be lubricated properly. This will increase friction and heat, leading to an overheating transmission.

When the transmission overheats, it can lead to severe damage. This is why it would engage limp mode so that the transmission’s performance would be limited and prevent damage.

Failed Clutch, Linkages, or Solenoid

If the clutch or linkages within the transmission has failed or been misaligned, your car may also engage limp mode. This is to prevent any more stress or damage to the transmission, saving you from an expensive transmission rebuild.

The linkage is responsible for shifting your gears, if it failed then the transmission will have trouble changing gears. This is why it engages limp mode as your car will only use one gear in limp mode.

If you have an automatic transmission, you may have a faulty solenoid. A solenoid is an electro-hydraulic valve that controls the flow of transmission fluid and it is what allows the automatic transmission to change gears.

A bad solenoid will be unable to perform its job, disrupting the operation of the transmission. You will notice your transmission is slow to respond or even refuses to change gears. When the problem is bad enough, the car will turn on limp mode to preserve the transmission.

Sensor Malfunction

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The car is a very complex piece of machinery and it needs a lot of sensors to make sure everything works together perfectly. Most modern cars will use a speed sensor, a Manifold Absolute Pressure (MAP), and a Throttle Position Sensor (TPS) to feed the car’s computer with various information about the car’s condition.

It then uses this information to tell the transmission when to upshift or downshift. For example, if the car detects you’re putting your foot down, it will automatically shift gears down because it’s assuming you want more power and you want to go fast.

How does this cause the car to go into limp mode? Well, your car’s computer is designed to receive information in a pre-programmed range specified by the manufacturer. If it receives information outside of this range, it will engage a “secondary” programming or in other words, limp mode.

For example, let’s say the TPS is supposed to send information between the value of “1-10”. If your car’s computer suddenly receives a value of “12”, it will assume that there’s an error with the TPS sensor.

It then engages limp mode to prevent any damage from happening. This of course is an oversimplification, but that’s generally how it works. If the sensor malfunctions, it may send incorrect information which puts the car in its fail-safe mode.

Damaged Wires

Since there’s a lot of sensors and electrical components, there are also a lot of wires in your car. Dirt, road debris, or even rodents finding their way into your car can damage your car’s wiring.

If there’s damage to the wires, the sensor and other electrical components won’t be able to send the correct signals and information to your car’s computer. This leads the computer to think that there’s a malfunction with a certain component.

This is basically the same as the sensor malfunction. But rather than because of a faulty sensor, the problem stems from wiring damage.

Signs Your Car Is In Limp Mode

Not sure if your car is in limp mode? These are the signs that your car is in limp mode:

Limited Speed, RPM, and Transmission

The first sign you will see is a limit to your car’s performance. The computer will limit your car to about 30 – 45 mph, and your engine usually won’t be able to rev over 3,000rpm or so. If you have an automatic, your car will also limit the transmission. Usually, it won’t be able to go over third gear, or sometimes limiting it to just one gear altogether.

Slow Acceleration

Not only speed is limited, but the engine power output will also be very limited. This means your car won’t have as much power as usual, and acceleration will be very slow. Remember, the purpose of limp mode is to prevent damage by preventing your car’s component from working as hard as usual.

Check Engine Light

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The check engine light will usually accompany limp mode. If you see the symptoms above and the check engine light is on, then your car is in limp mode. A check engine light is there to warn the driver that there’s an issue with the car’s powertrain.

Your car may illuminate the check engine light before engaging limp mode. This usually happens when the issue isn’t serious enough, so it will still allow you to drive as normal.

This is why you shouldn’t ignore a check engine light. It indicates an issue with either the engine, the transmission, or the exhaust system and you should address it before it gets severe. Ignore it long enough and the car will engage the fail-safe settings.

What To Do If Your Car Is In Limp Mode

It can be quite startling when you’re driving normally and then suddenly your car just isn’t performing as it normally would. But don’t panic! As mentioned, the limp mode is your car’s self-preservation mode, meaning it’s doing everything it can to prevent severe damage to the powertrain. Here are our tips on what to do if your car is in limp mode:

  1. Stop your car to the hard shoulder or an uncrowded part of the road so that you’re out of the way of other motorists.
  2. Put the transmission in P or Park.
  3. Turn off the engine and the ignition switch, then wait for about 60 seconds.
  4. Turn the engine back on and try driving away again. If the car is out of limp mode, then continue driving as you normally would. It might just be an error that caused the limp mode. But we recommend not pushing the car too hard and take your car to a repair shop later on for a diagnosis.
  5. If the car is still in limp mode, drive back home or to a repair shop carefully. Go to whichever is the closest, the sooner you stop driving, the better. Stay on the right lane since you won’t be able to go very fast.

However, there are some scenarios where you shouldn’t continue driving in limp mode:

  • You shouldn’t continue driving if the engine is overheating, pay attention to the temperature gauge.
  • The oil warning light is on.
  • If the check engine light is flashing, stop driving immediately. Under no circumstance, you should be driving with the check engine light flashing as it indicates a serious issue and can damage the car. You need to tow the car.
  • If weird noises are coming from the engine or the transmission, stop the car.

How To Fix Limp Mode

So, how do you get your car out of limp mode? As mentioned, the main cause is usually a transmission issue. When the transmission doesn’t have enough fluid and overheats, the car will limit performance to help prevent damage. So, naturally, you should check the transmission. But here’s what you can do first:

Turn The Car Off And Let It Cool Down

It’s also possible that the transmission is overheating because of external factors such as the weather. If you live in a hot climate or are driving during a heatwave, while unlikely, it’s possible that the transmission is overheating because of external temperature.

Turn off your car until it cools down and then turn it back on and see if the car is still in limp mode. If it’s not, you can continue driving until you reach home. However, we recommend checking your transmission fluid level. A low transmission fluid level is the most likely culprit for your car going into limp mode, here’s how you can check it:

Check The Transmission Fluid Level

Here’s how to check your car’s transmission fluid level:

  1. Most cars have a transmission fluid dipstick. This is usually located at the back of the engine is marked with a red handle that sometimes says “Transmission”.
  2. You should check the dipstick when the car is still warm. Some cars may even require the engine to be running to get an accurate reading. Check with your owner’s manual on whether or not the engine should be running.
  3. Make sure you’re on a surface level, then pull out the dipstick.
  4. Wipe the stick with a rag, and then reinsert the dipstick. Ideally, you should wipe it with a white rag or tissue. This way, you can see the color of the fluid. If it’s red, then it’s good. If it’s dark red or even black, it’s a good idea to replace the transmission fluid.
  5. Pull it out again and see where the fluid level is. The dipstick will have Maximum and Minimum markers on it. If it’s below the minimum level, you’re going to have to refill that. Possibly change it entirely with new fluids.

Here’s a video to help you understand how to check your transmission fluid level:

Add Transmission Fluid And Check For Leaks

If you need to add transmission fluid, the first thing you need to do is check what type of fluid you should use. You should be able to find this in your owner’s manual. Once you got the correct transmission fluid for your car, use a plastic funnel to insert the fluid through the dipstick tube. Since you’re only topping up, use about one quart. Afterward, check if your car has enough fluid. If it’s still low, add a quart at a time until it reaches the appropriate level.

Once you sort that out, you should check for leaks. Transmission fluid rarely needs topping up, so if your transmission fluid was low, you may have a leak. Check underneath your car if any red fluids are dripping off from the front-middle to the middle of the car. If there’s a red or dark red fluid dripping off, you have a transmission leak and you will need to fix that.

The cost to repair a transmission fluid will depend on where the leak is coming from. If the lines, rear gasket or seals, or the pan bolts are the source of the leak, it should cost you no more than about $200 – $250 to repair. However, this gets expensive if the leak is coming from the front seals or gaskets of the transmission.

This is because replacing those seals or gaskets will require your mechanic to remove the transmission from the car, and that will take some time and adds labor costs. The average cost is somewhere around $400 – $600 but can easily get to as high as $1,000 for certain cars.

We wrote a comprehensive guide on transmission leak repairs and you should read it if you need to fix a transmission leak.

What If the Transmission Fluid Is Fine?

If the transmission fluid is still at the appropriate level, your next step should be scanning the On-Board Diagnostic (OBD) system with an OBD scanner. As mentioned, the limp mode is usually accompanied by a check engine light. The check engine light is your car’s way of telling you that there’s something wrong with the powertrain.

The system works by using several different sensors that feed information to the Engine Control Unit or Powertrain Control Module. When it detects an irregularity, it will try to fix that on its own. If it can’t get rid of the problem, it will register an error code which will then triggers the check engine light.

You can scan and find out the error code by scanning the OBD port with an OBD scanner. These error codes can’t tell you exactly what’s causing the problem, but it will help you identify where the problem is and narrows down the possible causes. This makes the diagnosis process much quicker.

To scan the OBD, you will need an OBD scanner or reader. If your car is made in 1996 or after, then you need an OBD-2 scanner. They’re usually around $30, or you can buy a good one for around $100. No need to spend thousands of dollars on the professional ones as those are intended for mechanics. And don’t worry, OBD-2 is universal and will work with any car.

How To Use An OBD-2 Scanner

Limp Mode

Once you got a hold of the OBD-2 scanner, here’s how to use it:

  1. Plug the reader into the car’s OBD port. This port is often located underneath the dashboard area, either above your pedals or knee. Keep in mind that some cars might have their port hidden out of sight. Check your owner’s manual or online to see where it’s located in your car.
  2. Once plugged in, turn on the OBD scanner. It should immediately scan the car. However, some scanners might require you to input additional information such as make, model year, VIN, etc.
  3. It will then display the error codes it has found. A more complicated scanner might also display a description of what’s wrong with the car, but if you have a simpler scanner then you should take note of the error codes on display.
  4. Afterward, check what the error codes indicate. This will help you diagnose the car and narrow down the possible causes.

Here’s a video guide on how to use an OBD-2 scanner:

Here are some error codes you might see and what they mean:

Possible Error Codes

  • P0218: Transmission Over Temperature. This error code means that your transmission is overheating. If the fluid is at the correct level, then check its condition if it needs replacing. It’s also possible you have a faulty solenoid that’s disrupting the flow of fluid into the transmission which causes it to overheat. A transmission fluid change costs somewhere between $100 – $400. Meanwhile, a pack of new solenoids will set you back anywhere between $250 – $600 including labor.
  • P0300 – P030x: Ignition System Misfire. These error codes mean there’s a misfire inside the engine. P0300 means there are multiple misfires, while a number at the end of the code specifies which cylinder is misfiring. For example, P0301 means that cylinder one is misfiring. A misfire is usually caused by bad spark plugs, and this can cause the car to go into limp mode if the problem is bad enough. Spark plugs are no more than $50 a set to replace, but if your problem stems from ignition coils, then they can be as high as $270 to replace.
  • P0101: Mass Air Flow (MAF) Malfunction. The MAF is a sensor that measures the amount of air the engine is taking to help control the fuel-air mixture. If the MAF detects an irregularity, it will send an error code. The P0101 code can mean a number of things, including dirty or fault MAF, damaged or disconnected air intake boot, a vacuum leak, or a clogged air filter or catalytic converter. Since the MAF plays a major role in your engine’s operation, a malfunction may trigger the limp mode. A MAF replacement cost is usually around $240 – $330.

If You See Other Error Codes

There are tons of other possible error codes that you might see, and there’s no way we can list them all down here. These are just some of the common ones you might see if you experience limp mode. If you see other error codes, you should be able to find what they mean in your owner’s manual. There are also tons of information online on what error codes mean. Once you find what they mean, then you can find out what might be causing them and find a fix.

After you fix your car, the check engine light may stay on and needs to be reset. You can clear the light by clearing the error codes using the OBD scanner after you fix the problem. Do not clear the error codes before you fix the problem and do not ignore the check engine light.

Limp Mode: Conclusion

Limp mode is your car’s way to prevent severe damage to the powertrain unit by limiting performance. This prevents the powertrain from working too hard and avoiding severe and expensive damages. If your car is in limp mode, you can continue driving as long as there are no weird noises, no flashing check engine light, and the engine isn’t overheating. But the sooner you stop driving, the better.

If the limp mode goes away on its own, you should still check your car and see if it has any problem. It’s possible that hot weather was overheating your car’s transmission which causes the car to go into limp mode. But it’s more likely that you have an underlying problem with the powertrain unit. Check and fix the problem if there are any to avoid expensive repairs in the future.

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