Most newer cars are intelligent enough to protect themselves from excessive damage when certain systems run amuck. Once one of those systems begins malfunctioning, it sends an alarm to the car’s computer network. It reduces the vehicle’s power and speed to prevent further harm. This effort is known as “limp mode.” It is a function of gasoline-fueled vehicles; however, electric vehicles (EVs) have their own version of limp mode (also known as turtle mode), which we discuss in more detail below.
We will explain limp mode, list some of its causes, symptoms of your car in this state, and a few preventive measures. To skip ahead, use the links below.
A car’s limp mode is a security feature that kicks in when the vehicle’s computer network detects an issue with one or more of the critical systems. Also called “limp home mode,” the feature activates to prevent damage to your car and its components. It accomplishes this by slowing the car through the transmission, throttle control, or electronic control unit.
Limp mode reduces power and turns off things like your air conditioning, minimizing further harm while allowing you to get home, to a car service center, or simply out of the flow of traffic.
Turtle mode is the electric vehicle (EV) version of limp mode, activating when the remaining charge in the EV battery falls below a certain level. Where limp mode’s goal is to protect expensive components in a combustion vehicle, turtle mode’s objective is to conserve battery power long enough for the EV to reach a charger. Most EV manufacturers don’t quote a percentage of charge below which turtle mode activates, but 10% is a good rule of thumb. Why 10%? Because completely draining an EV battery shortens its lifespan. Don’t do it! In fact, to help maintain EV battery health, most experts recommend never letting the charge fall below 20% and never charge above 80%.
RELATED: 5 Signs Your EV Battery Could Be Dying
If you have been ignoring the multiple alerts appearing on your EV’s driver-information screen warning that your battery charge is dangerously low, you will know your EV has slipped into turtle mode when two things happen. First, the LED turtle mode icon will illuminate on your EV’s driver-information screen, and second, your speed will noticeably reduce. At this point, the speed reduction might be gradual or immediate to a maximum, in some cases, of as low as 20 mph.
To get out of turtle mode, simply add charge to the EV battery. Turtle Mode is a failsafe of sorts to conserve battery charge, allowing you to reach a charging station. If the EV enters turtle Mode and your gauges seem to be telling you there is plenty of charge, you can try pulling over and restarting the EV.
Virtually every modern car has some form of limp mode. This includes brands like Mercedes-Benz, Ford, Chevy, Kia, and so on.
Limp mode is as serious as the issue that activates it. In other words, it may be severe or as easy to solve as topping off a low transmission fluid level. Consequently, until you know which it is, your default reaction should be to take it very seriously. This is especially true if your car repeatedly goes into limp mode.
Any number of issues can trigger limp mode. Among the most common:
Generally, no, a faulty battery doesn’t activate limp mode. However, other electrical issues, such as faulty wiring and failing sensors, can cause a vehicle to go into limp mode.
Limp mode is a self-preservation function that protects your car. However, depending on where or when it activates, it can have the opposite effect. A sudden slowing in the middle of speeding freeway traffic can be downright frightening. Moreover, creeping along well below the speed limit on a busy street or highway can be dangerous and is always stressful.
If you’ve never experienced a limp-mode event, when it does happen, you may not recognize it for what it is. Here are some signs your car may be in limp mode:
The short blanket answer to whether driving in limp mode is OK is no. No, it isn’t. Having said that, a few culprits sending your car into limp mode are fairly innocuous. In other words, they don’t pose an immediate danger to your car’s health. In such cases, driving five miles to a service center or home likely won’t do any damage. However, it’s a roll of the dice. If the issue is serious, driving a few miles could cause expensive-to-repair damage. Our general recommendation is, if you find your car in limp mode, pull over and turn off the engine.
You should treat a limp mode activation as an alarm that your car faces a serious problem. Overriding or bypassing limp mode could lead to an even more serious issue, requiring expensive repairs. If your check-engine warning light is on and limp mode has engaged, the issue requires an onboard diagnosis of your car’s computer system.
If you have an OBD-II scanner, you can run the diagnostic yourself. Otherwise, you should immediately take your car to a trained technician. You can learn more about the diagnostic process at Kelley Blue Book’s Service Advisor. Having said that, there are a few steps you can take in the meantime.
Turn off the engine – Find a safe place to exit the flow of traffic and turn off the engine. Wait at least 60 seconds and restart the engine. As with rebooting a computer, restarting the engine may be enough to get the engine to perform normally. If the issue is overheating and you are close enough to home or a repair center, your car may operate normally long enough to get you there. However, the chance of limp mode reactivating as soon as the engine gets hot again is likely. If a transmission issue causes your car to go into limp mode, you may have trouble getting it out of Park and into Drive once it’s restarted.
Check fluid levels – Low engine oil, transmission fluid, or coolant levels can sometimes trigger limp mode. Check the levels and top off if necessary.
Dirty air filter – A dirty air filter will prevent the smooth flow of fresh air into the engine. Inspect your engine air filter. If it appears dirty, replace it.
The best prevention of limp mode is following the carmaker’s regular maintenance schedule for your car. Regular maintenance won’t prevent every cause triggering limp mode, but it will catch many causes before any damage is done. Regular engine tune-ups will ensure all the components are healthy and operating properly.
