Have you ever wondered how to get out of Limp mode or how to reset Mercedes Limp mode? Well, we got you covered.
Mercedes cars are known for their exceptional performance, sleek design, and luxury features. However, like any other vehicle, they can experience problems, and one such issue is the dreaded ‘limp mode.’
Here are 5 easy steps to take to get out of limp mode, which includes:
Step #1: Inspect the Fluid Level
Step #2: Scan for Unit Fault Codes
Step #3: Replace the O-Ring
Step #4: Reset Transmission Adaptations
Step #5: Replace the Valve Body
In this comprehensive guide, we will discuss what limp mode is, its causes, and symptoms, and how to reset it to get your Mercedes back on the road.
Table of Contents
What is Limp Mode?
Limp mode, also known as “limp-home mode” or “fail-safe mode,” is a safety feature built into Mercedes vehicles. When the car’s engine control unit (ECU) or transmission control unit (TCU) detects a problem with the vehicle, it activates limp mode to protect the engine and transmission from further damage.
In limp mode, the car’s power and functionality are limited, allowing you to drive to a nearby mechanic or get your car home without causing serious damage.
Symptoms of Limp Mode
If your Mercedes enters limp mode, you may notice the following symptoms:
- Check engine light: The check engine light may come on or flash when the car goes into limp mode.
- Limited speed: The car’s speed will usually be limited to between 30 and 45 MPH.
- Low RPMs: The engine will typically be limited to less than 3000 RPM.
- Unable to shift into high gear: Limp mode may prevent you from shifting past 3rd gear, or you may not be able to shift gears at all.
- Poor performance: Acceleration may feel sluggish, the car may feel jittery, and the engine may misfire.
- Disabled features: Unnecessary features like air conditioning may be unavailable.
Causes of Limp Mode
There are several reasons why your Mercedes might enter into limp mode. Some of the most common causes include:
1. Faulty Mass Air Sensor
The Mercedes transmission is very sensitive to the quality of the air entering the engine. A faulty mass air sensor can cause the transmission to enter limp mode.
2. Faulty Transmission Control Module
The transmission control module is responsible for controlling the shifting of gears in your Mercedes. When this module malfunctions, it can cause the car to enter limp mode.
3. Faulty Transmission Fluid Temperature Sensor
The transmission fluid temperature sensor monitors the temperature of the transmission fluid. If this sensor malfunctions, it can cause the transmission to enter limp mode.
4. Dirty Transmission Fluid
Dirty transmission fluid can cause several problems, including hard shifting, jerking, or slipping. It can also cause the transmission to enter limp mode.
5. Electronic Throttle Actuator Problems
The electronic throttle actuator controls the amount of air entering the engine. If this actuator malfunctions, it can cause the transmission to enter limp mode.
6. Corroded Computer Module Contacts
Mercedes transmissions use a computer module to control gear shifting. If the contacts on this module are corroded, it can cause the transmission to enter limp mode. Contacts can corrode due to moisture or dirt.
How to Reset Limp Mode in Mercedes
Once you have identified and fixed the issue causing limp mode, you can attempt to reset it. Here are some methods to try:
1. Restart the Engine
In many cases, simply turning off the engine and restarting it after a few minutes can reset limp mode. If the issue causing limp mode has been resolved, the car should return to normal operation.
2. Check Fluid Levels
Inspect the transmission fluid level and top it up if necessary. Low fluid levels can cause hard shifting, jerking, or slipping, and can also trigger limp mode.
3. Disconnect the Battery
If restarting the engine doesn’t work, try disconnecting the battery for a few minutes and then reconnecting it. This can reset the transmission control module and may fix the problem.
4. Scan for Fault Codes
Use an OBD2 scanner to scan your car for fault codes. These codes can help diagnose the problem with your transmission.
Clearing the codes may temporarily reset limp mode, but if a major issue persists, the check engine light will reengage, and the code will return.
5. Visit a Mechanic
If your car remains in limp mode after trying the above methods, it’s time to visit a mechanic for a professional diagnosis and repair.
What to Do If the Car Won’t Exit Limp Mode
If you’ve tried resetting limp mode but your car still isn’t functioning correctly, consider the following steps:
1. Inspect the Fluid Level
Check the transmission fluid level and top it up if necessary. Low fluid levels can cause various issues, including triggering limp mode.
2. Scan for Unit Fault Codes
Use a diagnostic tool to scan for unit fault codes. This can help identify the problem with your transmission. An OBD2 scanner can provide readings on your phone.
3. Replace the O-Ring
Sometimes, the issue can be as simple as replacing the O-Ring responsible for sealing the connection between the transmission and the cooler lines.
If this seal is damaged, it can cause transmission fluid to leak and lead to hard shifting or jerking.
4. Reset Transmission Adaptations
If you have replaced any parts in your transmission, you’ll need to reset the adaptations using a diagnostic tool. Resetting adaptations ensures that new parts are properly calibrated and functioning correctly.
5. Replace the Valve Body
The Mercedes transmission has a valve body that controls the flow of transmission fluid. If this valve body is damaged, it can cause hard shifting or jerking. You may need to replace the valve body if it’s damaged.
Limp Mode FAQs
Q: Will driving in limp mode damage my car?
A: Limp mode is a safety feature designed to protect your car from further damage. However, driving in limp mode for an extended period can damage your car due to overheating.
Q: How do I know if my car is in limp mode?
A: Signs that your car is in limp mode include the engine light turning on, limited speed, and the transmission making a whining noise.
Q: Can I bypass limp mode?
A: Bypassing limp mode is possible, but not recommended, as it can damage your car.
Q: Will DPF regeneration occur in limp mode?
A: No, DPF regeneration will not happen in limp mode because the process requires the engine to run at high speed, which is not possible in limp mode.
Q: How long can I drive in limp mode?
A: You should not drive for more than 30 minutes in limp mode, as it can damage your car.
Q: How do I fix a car that won’t go into gear?
A: To fix a car that won’t go into gear, check the fluid level, scan for unit fault codes, replace the O-Ring, reset transmission adaptations, and replace the valve body.
Mercedes Limp Mode Diagnosis and Repair. >> Check out the video below:
Mercedes vehicles can experience transmission problems such as hard shifting or jerking, which can cause the car to enter limp mode. Limp mode is a safety feature meant to protect your car from further damage.
You can reset limp mode by restarting the engine, checking fluid levels, disconnecting the battery, or using a diagnostic tool.
To prevent your Mercedes from entering the limp mode, ensure that the transmission fluid is at the correct level, the O-Ring is intact, and the adaptations are reset. These measures will help reduce the chances of your car going into limp mode.
Remember that if your car does enter limp mode, you should not drive for more than 30 minutes, as this can cause damage to your vehicle.