It doesn’t happen often, but sometimes your car will slow itself down. The engine won’t rev, and the transmission seemingly won’t shift out of second gear. The “limp mode” has been engaged, and all you can do is limp along a few miles per hour. What is limp mode? How did your car get into it, and what can you do about it?
Limp mode is a protective setting that your car engages when you have serious transmission problems. It allows you to move your vehicle slowly to a repair shop or at least a safe parking space without causing further damage. Limp mode means you can limp along to a mechanic and get the problem checked out.
If your car goes into limp mode, you should get off the road as quickly as you can and move it to a safe place. Limp mode doesn’t mean that you must stop your car right then and there. You have enough slack that you can move the vehicle out of traffic to a safer place.
What does limp mode mean?
Almost everything your car does is controlled by a computer. Sensors placed throughout the vehicle continually report their status to the computer. The machine is programmed with correct values for these measurements. If any of the sensors returns a measurement outside of the computer’s parameters, the computer reacts.
Some of the reactions are minor, while others can have a significant impact on what your car does. Limp mode is one of the strongest reactions your vehicle can have. When the computer gets messages from the transmission that there are serious problems, the computer takes strong action.
The results of this action are called limp mode. The transmission is limited to one gear – usually second – and the engine rpm’s are also limited. These actions protect the car from further damage. Neither the engine nor the transmission can drive hard enough to break anything beyond what’s already wrong.
What causes limp mode?
Limp mode can have a wide variety of causes. It might be an indicator of a severe problem, or it might just be a sensor malfunction. Here are some of the common issues that can trigger limp mode:
- Problem with transmission or clutch. If there is a mechanical malfunction with your transmission, the sensors will pick up that there’s a problem and shift the car into limp mode. Transmission and clutch problems usually mean expensive repairs.
- Bad wiring. Issues in the wiring harness have a variety of causes. Battery acid, heat, water, and physical damage from road debris or wrecks can all mess up the wiring harness. Damage to the wiring can cause the sensors to report a fault to the car’s computer. Wiring damage can be challenging to locate but is not usually difficult to fix.
- Low transmission fluid. Transmission fluid helps keep the transmission cool, lubricated, and protected. If your transmission leaks or the fluid level gets too low, the car may kick over to limp mode. Low transmission fluid is usually an easy fix – you need to add more fluid.
- Sensor malfunction. Transmissions and wires aren’t the only things that can break. Sensors break down to. A damaged sensor will report erroneous information to the computer, triggering limp mode. Fixing a sensor is usually much less expensive than fixing the whole transmission.
Solutions for limp mode
There are two kinds of solutions when your car goes into limp mode. First, there are temporary fixes the get you back up to speed. Second, you can apply a permanent fix that truly repairs the problem.
The easiest temporary fix is to turn the car off, wait a few seconds, then turn it back on. A slightly better fix is to turn the car off, remove the key, and walk away for a while. Turn the car off and back on triggers a new round of diagnostic checks that may result in the computer getting an all-clear signal from the auto.
Letting the car sit for a while can help by letting things cool down. If the sensor is triggered because the transmission overheats, allowing the vehicle to sit and cool off makes a difference. The part can cool down, and the car can get ready to work again.
These two fixes may let you get your car back up to speed, especially if the problem is with a sensor or wiring. Sometimes the computer just gets an odd reading and throws the car into limp mode. If the vehicle keeps switching back into limp mode, or if these fixes don’t work, you need a permanent repair.
Repairing the problem
If your car won’t stay out of limp mode, it’s because there is something wrong with it. The computer knows that something is broken, and it won’t let you run the car full-out until you get the part fixed. You need to see a mechanic.
To understand why your car keeps going into limp mode, you need to ask the computer what’s wrong. For that, the vehicle needs to be hooked up to the best OBD2 scanner. These scanners are electronic devices that communicate with the computer to show error codes to the mechanic. By looking up the error code, the mechanic can diagnose the problem and tell you how to fix it.
Depending on the problem, keeping your car out of limp mode can be cheap or very, very expensive. You won’t know until you put the computer up to the scanner to find out.
Limp mode for your car is kind of like your body running a fever. It’s an indicator that something is wrong and needs attention. Sometimes just a little bit of rest is all you need, while other times, it takes a trip to the doctor to even figure out what’s wrong.
If your car goes into limp mode and turning it off and back on doesn’t help, you need to see a mechanic. The mechanic can hook your vehicle up to an OBD2 scanner to find out what’s wrong. Once you have gotten the problem diagnosed, you can make a decision about fixing it.