When your Mercedes fails to shift out of first gear, it can be a frustrating and potentially harmful experience.
This issue not only affects your driving experience but also the overall performance and safety of your vehicle.
Follow the steps below if your Mercedes won`t shift out of the first gear, which include:
Step #1: Determine if the car is in limp mode or not moving
Step #2: Check the transmission fluid level
Step #3: Use an OBD2/CAN scanner
Step #4: Inspect the fluid level and color
Step #5: Listen for a whine
In this comprehensive article, we will discuss the possible causes of this problem, and offer solutions to help you get back on the road as soon as possible.
Table of Contents
Understanding Transmission Limp Mode
What is Limp Mode?
Limp mode, also known as fail-safe or emergency mode, is a protective feature designed to prevent further damage to your vehicle’s transmission.
When your Mercedes enters limp mode, it gets stuck in one gear, typically second gear, and doesn’t shift to the other gear. As a result, your driving speed is limited to around 30 mph.
Why Does Limp Mode Happen?
Limp mode can be triggered when sensor input values from various sensors inside the transmission, valve body, Mass Air Flow (MAF) sensor, and other components fall outside their normal operating range. This protective measure is designed to safeguard the transmission from further damage.
It’s essential to note that just because your car has entered limp mode doesn’t necessarily mean you need a new transmission. However, you may experience a check engine light if your transmission goes into limp mode.
Top Reasons Causing Transmission To Go Into Limp Mode
Here are some leading causes for your Mercedes to enter limp mode:
- Mass Air Flow Sensor (MAF): A faulty MAF sensor could cause your transmission to go into limp mode.
- Shift Module: A defective shift module inside the car could also be responsible.
- Speed Sensor: A bad speed sensor may trigger limp mode.
- Brake Light Switch: A malfunctioning brake light switch could cause the issue as well.
- Transmission Control Module: A defective transmission control module may lead to limp mode.
- Old Battery: An old battery could also contribute to the problem.
Keep in mind that other factors not directly related to the transmission could also cause your car to enter limp mode.
Read also >> Can a Bad Throttle Body Cause Transmission Problems?
Troubleshooting a Mercedes That Won’t Shift
Follow these steps to troubleshoot your Mercedes that won’t shift:
- Determine if the car is in limp mode or not moving: In limp mode, your car will drive in second gear.
- Check the transmission fluid level: If the fluid level is low, add more as needed. If the level is correct and you hear a whine, you may have serious transmission problems.
- Use an OBD2/CAN scanner: Get an OBD2/CAN scanner that reads and checks engine/transmission codes. You’ll get a fault code pointing you in the right direction. Write that code down and use it for further investigation.
- Inspect the fluid level and color: Check the transmission fluid level, condition, and color. If the fluid is discolored or has a burnt smell, it may indicate a more serious issue.
- Listen for a whine: If you hear a whine, it could indicate that the fluid is not circulating properly within the transmission, which could be caused by a bad torque converter, a failing transmission oil pump, or water contamination in the transmission.
Understanding Mercedes-Benz Transmission Models
Mercedes-Benz has used different transmission models over the years. These include:
- 5-speed transmission (722.6): Introduced around 1994 and used up to 2007 models, this transmission is known for its durability and reliability.
- 7-speed transmission (722.9 or 7G): Introduced in early 2000, this transmission was first installed in some 2004 models. The 4MATIC models were the last ones to switch from the 5-speed to the 7-speed transmission.
How to Get Your Mercedes Out of Limp Mode
To get your Mercedes out of limp mode, you must first identify and fix the issue that caused it to enter limp mode.
Sometimes, the car will exit limp mode after the problem has been resolved. In more serious cases, you may need to reset the Transmission Control Unit complex codes using an advanced scanner.
Shifter Stuck in Parking
If your Mercedes is stuck in Park and won’t shift, the following components could be the culprits:
- Shifter Module: It could be defective.
- Brake Light Switch: This may be malfunctioning.
- Connection between the Ignition Module and Shifter Module: Older models used a cable to unlock the car from Park, while newer models use an electrical wire. Check for any issues in this connection.
Tip: Refer to your owner’s manual for instructions on how to manually get your car out of Park using a screwdriver or a similar object.
The Car Will Not Move at All When in Drive or Reverse
If your car won’t move in Drive or Reverse, listen for a whine. If you hear one, you may have serious transmission problems.
Some Mercedes models, such as E-Class and CLK-Class, had defective radiators that allowed coolant to mix with the transmission fluid, causing severe damage to the transmission. If you’ve experienced this issue and replaced your transmission, you must also replace the radiator to prevent further damage.
Standard Transmission OBD-II Codes
P0715 and P0730 are generic transmission codes that you may get from an OBD engine reader. These Diagnostic Trouble Codes (DTC) point to the transmission speed sensor installed on the conductor plate.
You can replace the conductor plate with the transmission still in the car, and it can be purchased for less than $200.
When replacing a defective shifter module in most Mercedes models from 2000 and newer, you’ll need a “virgin” or new shifter module that needs to be programmed to match your car’s VIN. Used shifters may only work in 2000 and older models, as well as:
- W210/W208 up to 2003
- R170 SLK up to 2004
- W163 up to 2004
Always verify if your shifter module needs programming before installing it in your vehicle.
If your Mercedes won’t shift out of first gear, it’s crucial to diagnose and address the issue promptly.
Follow the troubleshooting steps and solutions outlined in this article to help you identify the problem and get your car back on the road safely and efficiently.
Remember, it’s always best to consult a professional mechanic when dealing with transmission issues to ensure the problem is correctly diagnosed and resolved.