One of my unforgettable experiences in recent times was the day I was cruising on the highway in very high spirits, singing along to my favorite songs playing over the radio and oops…the ‘check engine’ light on my dashboard initially flickered and then lit up. My high spirits immediately ebbed and worse still, my car started stalling and vibrating. I knew there was a problem and I immediately parked by the side of the road and put a call across to my car repair man. I eventually got to know that my car entered what was termed as Limp Mode.
Do you know what Limp Mode is? Have you ever had an experience similar to mine? Well, this article will clear any ambiguities about Limp Mode in cars. It will also let you know how to bypass limp mode; and ultimately ensure that there’s no severe damage to your car. The aim of writing this article is to enlighten you on this subject to ensure that you continue to relish the optimum performance that you have always known your car for as well as get your money’s worth each and every time. Wouldn’t you want this? Sure, you would. So read on.
What is Limp Mode?
Interestingly, today’s cars are being designed with autonomous performance in mind. The application of artificial Intelligence in cars has made it possible for us to have self-driving cars, cars that understand and adapt to your behavior and preferences, and cars that detect problems in themselves and let you know what to do.
Limp Mode which is also termed limp home mode is a self-preservation mechanism in cars that enable them to detect faults and reduce performance till the car is safely driven to the shoulder of the road, driven to a nearby car repair workshop or simply limped home.
Technically, it is a conservative map or calibration used by the transmission control unit (TCU) or the engine control unit (ECU) of a car whenever a defect or fault is detected or sensed that is aimed a safeguarding the engine from severe damage.
Basically, Limp Mode is a safe mode that helps your car and also prevents you from being stranded. Instead of your car engine completely shutting off, it enters this safe mode to enable you manage or limp it to the nearest possible help.
How to Know Your Car Is In Limp Mode
When your car is operating on limp mode, apart from the lighting up of the ‘check engine’ light it will exhibit a range of characteristics that will let you know that all isn’t well. I will highlight the basic ones. They include:
You will notice that your car stalls and you are no more able to drive at highway speeds. There will be a drastic reduction in your car’s maximum engine speed also known as RPM. The technical explanation of this is that the delay timing for the sparking of each cylinder’s plug (the pull ignition timing) changes, there’s also a change in the timing of when the exhaust/intake valves open (the alter valve timing).
You will discover that you cannot engage more than the 3rd gear
If the problem is emanating from a faulty transmission, your car’s transmission will likely shift into the 2nd or 3rd gear and remain there. This will result in sluggish acceleration from a standstill or stop position and a relatively higher speed while on the highway.
Jerking and Vibration
You will notice minor to severe jerking and vibration as your car struggles to carry on.
How to Bypass Limp Mode
Sincerely, I would rather not recommend that you bypass limp mode unless when it’s your best option and you are fully aware of the possibility of severely damaging your car engine is anything goes wrong. The fact that limp mode was triggered off in the first place means that there’s an underlying fault and you could severely damage your power train when you continue driving your car using the same parameters.
That said, I will also add that the only reason why you may have to bypass limp mode is be able to drive your car to your car repair workshop for proper diagnosis and repair or simply to ‘limp’ It home. It is just a temporary fix.
Note that even if the bypassing works, your car may revert to limp mode if the underlying fault continues; so your best bet would be to postpone all other activities and seek help immediately. You may also need to drive by the shoulder of the road or take a less travelled road while doing that.
So, you can try doing the following:
Try Restarting the Car
Depending on the severity of the underlying issue, simply restarting the car could be your deal maker.
Allow the Car to cool down
It is advised that you allow the car to cool down. Firstly, all the volatile oils and fluids would have settled down and can be gauged correctly. It is also safer for you to work this way and surprisingly, you may discover that the computer will reset and limp mode will go away when the car cools down.
Connect an OBD2 Scanner
If the limp mode is still active, then your next best bet will be to connect an OBD2 Scanner. You can buy an OBD2 Scanner as a regular tool for your car. You will need to discover where it can be connected on your vehicle. Most times, it is connected under the dashboard by the driver’s side. Study the buyers guide effectively to enable you have the best user experience.
Scan for defects
You do this by simply pressing the scan button. The machine will scan and diagnose the fault and display a code(s). Search online to ascertain what the displayed code (s) indicates and you will identify the problem at hand.
Disconnect the battery cables and reconnect after about 15 – 30 seconds
This is another thing you can do to bypass limp mode. Simply remove the battery cables and hold them together and reconnect after about 15 – 30 seconds. This will dissipate any stored electricity in the system.
What are the Causes of Limp Mode?
A variety of factors can trigger off limp mode in your car. Some may be as a result of your car’s specific manufacture mode because different manufacturers implement different TCU and ECU standards. The most common causes include:
Knock or Engine Misfires
When your car experiences knock or engine misfires consistently, the limp mode function can be triggered. Well, the good news is that an intermittent knock while you are driving on the highway or a misfire once in a while won’t be anything to worry about. Almost all car engines experience a knock once in a while and in non-severe cases, the ECU will simply pull ignition timing shortly until everything is back to normal.
Sensor issues can also trigger of Limp Mode. This is basically because they make the ECU become confused due to the reception of wrong signals. Sensor issues can be in the form of faults, outdated sensor readings, or outrightly missing sensors.
When your car engine has no way of correctly reading the density of the air coming into the combustion chamber, then of course it will not be able to correctly inject fuel. Inaccurate injection of fuel is one of the leading causes of severe engine damage due to an increase in engine load and RPM.
Low Fluid Levels
Sometimes, it is the duty of ECUs and TCUs to monitor the levels of the various fluids used by your car. Whenever the engine oil is low or the level of transmission fluid is very low, there’s a resultant decrease in oil pressure which may in turn trigger off limp mode in your vehicle.
If your car is turbocharged, then the wastegate operation is controlled by the boost controller. The basic function of the wastegate is to allow flow of excess exhaust around the turbocharger instead of flowing through exhaust turbine. This basically helps to maintain the correct boost pressures.
When the boost pressure generated is more than the target boost pressure for the ECU for a lengthy time, an overboost condition arises. This fault is due to a failure of the wastegate solenoid or the boost controller and under this condition, a turbocharged vehicle is bound to enter limp mode to safeguard itself from severe engine damage like breaking of the piston rings, spinning of bearings and/or bending of the connecting rods.
Whenever your car overheats, the ECU will normally cut fuel supply to some cylinders so that the engine temperature is reduced by cool air.
How to Prevent Limp Mode
It would be unfair of me to write on how you can bypass limp mode without telling you how to prevent it. Check out the following tips:
- Routinely check the levels of your vehicle fluids and oils and top them up to the recommended levels. Such fluids include your brake fluid, automatic transmission fluid, engine oil, power steering oil and radiator coolant.
- Inspect your car wiring system to detect any burnt or disjointed wires and simply replace or repair them.
- Never ignore any warning signs such as a slow shifting gear, poor acceleration and unusual performance.
- Routinely study your car manual to be able to know your car better.
- Most importantly, never panic when your car goes into limp mode. Simply take your time and sort out the issues using the information I have provided. Everything will turn out just fine.
Bypassing limp mode in your car? Do you know better now? Sure you do and I’m happy to be of help.