What Is Limp Mode?

Limp Mode allows your car to be driven a limited distance at reduced speed when something is wrong and may cause severe damage or stop the vehicle from running, such as a problem related to the engine or transmission. Limp Mode typically limits engine rpm, engine power and road speed, and it may shut off the air conditioning and keep the transmission in one gear or not allow it to upshift into higher gears. While going into Limp Mode is certainly not good, it’s better than being left stranded — or being hit with a major repair bill.

Related: What Does the Check-Engine Light Mean?

Even if there isn’t a warning light illuminated on the dash that says “Limp Mode” or something similar, you’ll probably first notice that the car isn’t running properly. In many cases, the check-engine light or other warning lights will be on; a flashing check-engine light indicates a serious problem.

What to Do if Your Car Is in Limp Mode

If your car suddenly starts running poorly, the first thing to do is to look for a safe place to pull off the road. Not only is it dangerous to be going slowly in fast-moving traffic, but the car may soon shut down altogether — and it’s even worse to be stopped in fast-moving traffic.

Once you’re off the road, look for any warning lights that are on and check the gauges (such as the fuel gauge) to see if any are reading low. Either can be useful in figuring out what might be wrong. Warning lights would include the check-engine, low-fuel, oil-pressure, coolant-temperature, battery-charge or transmission warning lights. Some of these could lead you to something you could check yourself, while others would likely require a professional (or at least some special tools) to diagnose and repair.

While many running problems would at least trigger the check-engine light — which requires a special diagnostic tool called an OBD II (or OBD 2) code reader or scan tool to decipher — other warning lights may give you an immediate clue. Code readers can be purchased for less than $50 in most cases, are fairly simple to use and work for nearly every passenger vehicle made starting with the 1996 model year.

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What to Check For

For instance, if the oil-pressure warning light (which could look somewhat like Aladdin’s lamp), is on or the oil-pressure gauge is reading low, it would indicate you might be low on oil or have some other problem that’s restricting oil flow through the engine. (Low oil pressure can destroy your engine in fairly short order.) The first step would be to shut off the engine as soon as it’s safe to pull over and do so, wait a couple of minutes for the oil to drain back into the oil pan, and check the oil level. Be aware that having too much oil can also cause low oil pressure, as the engine’s spinning crankshaft can hit the oil and froth it up, and the oil pump can’t pump foam.

Similarly, a coolant-temperature warning light (which may look like a thermometer over water) or gauge may indicate the engine is overheating. In this case, you should turn the engine off as soon as possible. To check anything, you’ll need to open the hood, but be aware that it might be hot. One of the first things to look for is whether the serpentine belt is still in place. This belt often turns the water pump, so if the belt breaks, the water pump will no longer circulate coolant, and the engine will overheat. It also turns the alternator, so the battery-charge light (which might look like a car battery) may be on, as well. In some cars, the belt turns the power-steering pump, so turning the steering wheel might be difficult; other cars have electrically assisted power steering, which wouldn’t be affected.

If the belt looks OK, check the coolant overflow tank, which should have at least some coolant in it. If that tank seems empty, wait for the radiator to be cool enough to touch (which will likely take a while), and then open the cap and check your coolant level, which should be at or near the top of the filler neck. It’s important to not open the radiator cap while the radiator is hot as scorching coolant can spew out.

Another thing you might be able to check is your air filter and any hoses leading to it, as the latter can get filled with debris (e.g., leaves or a rodent nest). However, this may require tools you may not have with you.

If there is no indication of low oil pressure or high engine temperature, look for any warning light that indicates a transmission problem (which may look like a gear, perhaps with a thermometer in the middle). Either way, it’s a good idea to check the transmission-fluid level. Steps for checking the transmission-fluid level differ, so consult your owner’s manual for the proper procedure or do an internet search for, “How do I check the transmission fluid level in a [year/make/model]?” Note that some vehicles don’t have a transmission-fluid dipstick; thus there’s no easy way to check transmission fluid. On many cars, checking the transmission-fluid level is supposed to be done with the engine warm and running and the transmission in Park. If you’ve shut the engine off already, you can try waiting about 15 minutes and then attempt to restart it.

If the engine fires up, you may find that it runs OK. This can happen because shutting off the engine may have allowed the car’s computer to reboot, erasing whatever problem caused it to force the car into Limp Mode. You might still want to take this opportunity to try to get the car to a repair shop to have it checked out, or at least a safer place to leave it. But don’t be fooled into thinking everything’s suddenly fixed. Cars rarely manage to fix themselves; even if the check-engine light is off, a mechanic may still be able to determine what caused the problem by checking for trouble codes that may be stored in the computer’s memory.

Something that can cause your car to run poorly that might not set off any warning lights is a failing fuel pump or clogged fuel filter. Unfortunately, there’s nothing you can do to diagnose or fix that at the side of the road, as it requires tools and equipment to do either.

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