What Is Limp Mode | Limp Mode Car Protective Actions

What is limp mode car?
What are the limp mode protective actions
Limp mode example
How the computer determines that the sensor is incorrect
What should you do when it goes into the limp mode?
What should you ask yourself

What is limp mode car?

The limp mode car or the fail code may occur when a computer has some difficulties or troubles with its logic. When the signal which doesn’t fit the program comes to the computer, another program switches on in order to protect the car from damage.

When all the conditions are in normal range and all signals from MAP, TRS, and other speed sensors are performing well, the transmissions and other car systems will operate normally. And if there are any differences in standards and the current situation, the main computer will be automatically switched into the emergency program.

When measures are getting out of the acceptable the computer and process the numbers, depending on how terrible is the situation, the computer reacts and changes the program.

ALSO READ: remanufactured transmission 1999 Honda Accord

What are the limp mode protective actions

If the computer detects the negative influence on the car it will turn the engine light to alert the driver to take measures and to check the transmission. While taking the diagnostics with a help of special programs and the scanner it is possible to get the soft codes.

If a rebooting or a restart will cure the problem that means that car status is quite ok, everything needed is to replace the sensor or to fix the connection. If such measures didn’t change the situation, the problem may be worse.

If the signal value is far far away from the acceptable values, the computer starts running the survival limp mode. In this mode, the computer just shuts off the electronic shift solenoids. From now on your car won’t switch 4^th and upper shifts, 2^nd and 3^rd allowed only. In addition, in order to protect a clutch, the pressure is set to high, the pressure sensors are also turned into “full on” to avoid damage.

That is how the limp mode looks like. In contrast to a car without such systems, you will be informed about possible troubles beforehand and the most important you have a chance to limp home or to the nearest service center minimizing the risk to damage the car completely.

Limp mode example

There might be a situation when the transmission goes into the limp mode because of losing connection with one of the sensors. In this case, the computer will say that it probably damaged or detached. As the harness is detached, the signal to go into the limp mode cannot be sent to the transmission. At the same time, solenoids are powerless and the line pressure is set too high, so the transmission is stuck in the proper gear – the same limp mode does.

How the computer determines that the sensor is incorrect

Let us say that TRS sensor, for example, sends to the computer a signal that the gas pedal is to the floor while the throttle is actually closed. Obviously, the computer will compare this information with speed sensors and will make a decision that limp mode is required and will turn the engine light on. A value from the sensor may not be an error at all, but if we compare all the information it becomes clear what is going wrong.

The founded fault code is recorded by the computer. In the service center, the mechanic will use a special reader that can check the recorded codes and figure out the problem with a help of the code table. Some readers can show the trouble itself without any other actions.

READ ON: Mercedes W211 torque converter problems

What should you do when it goes into the limp mode?

Now imagine you have got into the limp mode. The first thing you have to think about is how to fix it as soon as possible. So what should you do:

Do not panic at all! The Limp mode doesn’t mean that car turned into a stone, you can easily cope with all troubles in the nearest service center.
It is better to find the nearest service.
If the nearest safe place is a home, drive there immediately. Then you may call for service.
If driving on low speed makes you nervous, call for a tow.
Don’t make your car suffer more in limp mode, drive carefully.

What should you ask yourself

When your car is in safe, you can breathe out and think for a while. Ask yourself some questions to make the diagnostics easier and faster:
What was the speed before the error and for how long you have been running when the problem issued?
What was the circumstance that led to the engine lights?
What measures have you taken in order to maintain your car properly?
Are there any other symptoms that could bring such troubles?