Any make, your vehicle is engineered to protect itself from suffering catastrophic damage. This is essentially where the engine has to fail safe mode comes into play. Some people call it limp mode, and in other instances, it’s referred to as an engine cut-off safety feature. Regardless of the name, understanding what an engine fail safe mode is, what to do when it happens, and how it’s fixed will help you prepare for this unfortunate and highly stressful situation.
Table of Contents
What is Safe Mode?
Limp mode is a security function for your engine and transmission. When the transmission control unit recognizes a seriously wrong parameter from the engine or transmission, the car will go into limp mode. The limp mode often reduces the power and limits the engine’s RPM to drive your car to a workshop without damaging the engine.
Many car owners do not take enough notice of the engine light. Therefore the engine computer sets itself to limp mode, shuts off the turbo boost completely. And puts a max RPM limit to 3000 RPMs to be sure that you won’t blow or damage any engine parts.
Symptoms of Safe Mode
There are a few key symptoms and signs that can help you determine if the limp mode is occurring in your vehicle. Noticing these signs and symptoms can help keep you safe and prevent further damage to your vehicle.
1. Limited Speed And RPM
If limp mode is activated, your car will show a wide range of symptoms. Limp mode is in charge of limiting the amount of power to your engine and transmission, limiting the RPMs as well. Your driving speed will be reduced to a small range of miles per hour, usually between 30-45. This will make it impossible and dangerous to drive on a highway since you can’t drive at the correct speeds. You might be unable to shift above third gear.
2. Poor Performance
If your car is in limp mode, your acceleration will be very slow and you may be able to feel your engine shivering or shaking while trying to fire. Your transmission may automatically downshift without you meaning to. Even though you might be trying to drive at higher speeds. In case you are unable to shift above third gear, this is a common sign of limp mode. In addition, sometimes you can’t even shift your gears at all. So you remain stuck in the certain gear you are already on.
3. Check Engine Light Comes On
The check engine light can illuminate or flash repeatedly and will differ depending on the type of failure you have. You may notice your vehicle is overheating, which is a sign that you need to stop driving immediately. Give your car time to cool off to prevent any extra damage to the engine and transmission before you begin to drive again.
Common Causes Of Engine Fail Safe Mode
Along with the signs and symptoms of the limp mode being activated, certain causes turn the safe mode on in the first place. Knowing the causes of limp mode can help you identify the issue and prevent it from happening in the future.
1. Low Fluid Level
Low fluids, specifically the transmission fluid and oil, can cause a vehicle to enter limp mode. The transmission fluid is important in lubricating the surface and parts of the transmission system to reduce friction. And it also prevents the components from wearing out over time. The transmission fluid is supposed to be in your vehicle for the entirety of the vehicle’s life. Although some mechanics may want you to change the fluid every 50,000 miles.
A low fluid or transmission level can cause the limp mode to turn on. The low transmission fluid can cause low pressure, which prevents the transmission from operating properly.
2. Failed Clutch Or Transmission
If the clutch within your vehicle is damaged, broken, or faulty, then safe mode may be turned on. And it leads to the engine fail safe mode. In case the linkage is improperly adjusted, or there are bad solenoids in the transmission, this can activate limp home mode to prevent extra damage.
Automatic transmission linkage in every car has the same function. Its job is to shift the gears so the car can change speeds. A broken linkage will occur due to internal transmission poodles, such as the bands coming loose over time of the transmission getting too hot and wearing on the internal gears of the transmission. In case this occurs, it will place additional stress on the linkage, wearing this mechanism over time. The linkage is what is in charge of turning the gears or shifting them, so a broken linkage is a huge problem to gear shifting.
If the linkage is improperly aligned instead of broken, the linkage must be readjusted to properly align the corresponding gear. The linkage can become loose doing normal operating conditions due to high vibrations and shifting occurring. In case the linkage becomes misaligned, the gears and linkage will need to be readjusted.
3. Solenoid
The solenoid could cause the car to go into limp mode if there are issues with the solenoid’s condition. The solenoid in the starter is in charge of moving metal contacts into place, closing the circuit. It sent an electrical current when you turn your key in the ignition, triggering the magnetic field, and closing the circuit. If the solenoid is damaged, this process can’t happen correctly, and limp mode will turn on.
4. Sensor Malfunction
Within the engine and transmission systems, there are a few sensors that aid in controlling the mechanisms. If one of these sensors or speed sensors is sending incorrect signals to the computer, the limp mode can turn on. The sensors, like the MAF, MAP, and TPS, might all misfire and can cause the limp mode to be activated. Failed fuel injectors or coil packs can also cause the limp mode to turn on.
You will be able to tell if your MAP sensor is faulty or damaged. In that case, your vehicle has poor fuel economy, lack of power, failed inspection, rough idle, trouble starting, or stalling while using. If your MAF sensor goes bad, you will be able to tell by the vehicle having trouble starting, lacking power, and have poor acceleration.
5. Damaged Wiring
If your wiring is damaged or broken, this can cause the limp mode to turn on. Wires can be damaged by heat, debris, or acid leaking onto them, causing corrosion and wear over time. A damaged wire is unable to send the right electrical signal, causing the computer to think that a part has failed within the car.
6. Check Engine Light Is On
If your car is showing an orange check the engine light on your dash. This could be the reason your car is now in engine fail safe mode. In case you have been ignoring this signal as it has been glowing on your dashboard. This can be the signal of a much bigger problem that you have not taken care of. If you don’t treat your car issues for a long period of time, it can lead to worse symptoms and after-effects.
How Do You Reset Limp Mode?
If you know that the transmission issue was temporary, then you can reset the limp home mode by following these steps.
- Bring your car to a complete stop.
- Shift your automatic transmission into PARK.
- Turn the ignition switch to OFF.
- Wait 10 seconds.
- Turn your vehicle back on.
- Select the gear of your choice.
How Do You Fix Limp Mode?
Estimated Limp Mode Repair Cost
Some problems are more common than others when it comes to limp more. Here are the estimated repair costs of some parts that often result in limp mode. Prices include labor and part costs but do not include diagnosis costs.
Boost control valve replacement about 50$ to 150$, Boost pressure sensor replacement about 50$ to 100$, Wastegate replacement about150$ to 250$, Turbocharger replacement about 500$ to 1500$ and MAF sensor replacement about 200$ to 400$
Conclusion
If your transmission is in limp mode, your transmission has a problem and you should get it fixed as soon as possible. Here is what you should do:
- Do not panic. Limp mode is specifically designed to limit further damage and allow you to get your car to a service center.
- If possible, drive directly to a service center.
- Otherwise, drive home and call a service center to have your vehicle towed,
- If you do not feel comfortable driving at a limited speed, pull off the road where it is safe to do so and call for a tow.
- It is advised that you do not continue to drive a vehicle in limp mode as it is unsafe and can cause further damage to your vehicle.
