Came across thought to share:
In this article, we discuss the most common Mercedes-Benz transmission problems and how you can fix some of them. This troubleshooting guide will help you narrow down the transmission problem and teach you how to perform some of the repairs.

If your transmission is stuck in limp mode, DON’T PANIC. The majority of the time, the problem is not as grave as you may think.

If your transmission is stuck in gear and you are far away from home, try this:

Pull over and turn the car off. Remove the key.
Do not press the gas pedal or any other buttons on the car.
Wait 20 seconds.
Start the car and drive to see if it is out of limp mode.
Your transmission may be back to normal but there may be underlying issues that you need to address. If you ignore them, the car will start going into the limp mode more frequently. Don’t forget that first warning! You need to find the reason your transmission is going into limp mode or not shifting.

You would be surprised to know that the majority of the transmissions problems such as hard shifting and no shifting issues come from incorrect transmission fluid level or the infamous transmission 13 pin connector plug O-ring. These are easy fixes that you can even tackle yourself. Mercedes-Benz transmissions are very solid, and whole transmission replacement is very rarely needed. The 5-speed transmission that was used between 1995 up to 2008 is one of the best transmission ever built. Now let’s see if we can help you troubleshoot your transmission.

Top 5 Mercedes-Benz Transmission Problems.

1. Low Transmission Fluid
2. Transmission wire harness 13-pin (O-ring) connector oil leak/contamination
3. Valve body or conductor plate defective
4. Won’t come out of Park gear due to a defective brake light switch. (DIY How to replace the Brake Light Switch)
5. Defective Shifter Module

Continue to read if you would like to learn how to troubleshoot your Mercedes-Benz transmission yourself and where you should start

Transmission Troubleshooting Guide Step-by-Step

1. Check Fluid Level

You want to start with the most common and least expensive problem. That is verifying that the fluid level is not low. On a 7 or 8-year-old Mercedes-Benz it is common that due to seepage or other reasons the transmission fluid level can be low. The car will go into limp mode as soon as it detects low level. The car doesn’t come with a dipstick to check the transmission level but you can order one online for under $20. You will need Dipstick Tool for 722.6 722.9 Mercedes-Benz Transmission for measuring fluid level. Watch the video below to learn how to check the transmission fluid level on your Mercedes-Benz.


https://www.youtube.com/watch?v=znYgO5swYnA


2. Read and Clear Transmission Control Unit Fault Codes

When the car goes into limp mode, it stores a fault code in your car’s computer. Specific codes related to the transmission are stored in the TCU (Transmission Control Unit) and come generic codes such as P0705 are stored in ECU (Engine Control Unit). You don’t need to pay anyone to read the codes; you can retrieve them yourself in a couple of minutes with the right OBD II scanner. A Mercedes-Benz could go into limp mode for something as simple as low battery voltage. If that is your case replace your battery and use an OBD-2 scanner capable of clearing the fault codes from the transmission control unit. More on this latter.

In the video below we show you how to use a diagnostic scanner to troubleshoot your transmission, read and clear fault codes.



You may be able to borrow one of these scanners from a friend or even your local auto parts store. Your other option is to get one from Amazon, but you need to know what works on Mercedes-Benz cars. These scanners will cost you about the same as a diagnostic at a repair shop would, except you get to use it over and over again. Here are two of our favorite scanners that will read and erase trouble codes from transmission control unit on Mercedes-Benz cars. Note that these work on 1996 and newer MB cars. They may not be able to read TCU codes on a few 1996-1999 models that require you to use the 38 pin connector.

OBD-2 Scanners that can read and erase MB Transmission Control Unit

A. icarsoft mb ii
iCarsoft MB II for Benz/Sprint/Smart
Full MB control unit diagnostics. Including Engine, Transmission, ABS, Airbag, SRS, SBC Brakes, ESP, EPS, Air Suspension and more.

In depth troubleshooting, but only works on MB cars.
Troublshooting mercedes benz limp no shifting problem

B. Launch Creader X431 VII works in European, Asian and Domestic Cars.
ECU, TCU, AirBag / SRS, Transmission only. This can read and clear codes of the four systems mentioned. Works on most cars and models including Honda, Toyota, BMW, Lexus etc

Either one of these two scanners would get the job done. An advanced diagnostic scanner such as the iCarsoft or the Launch Creader listed here are a must for do-it-yourself Mercedes-Benz repair. They are affordable and can access most of the systems on your Mercedes-Benz including Airbag, EPS, ETS, Transmission, Engine, front and rear SAM, SRS, brakes and a lot more.

NEXT

3. Replace 13 Pin Connector Adapter Plug O-ring

transmission o plug 722.6You scan the car, and you may get fault codes that point you to communication problems with the valve body or incorrect gear ratios and similar. Before you spend hundreds of dollars on a new valve body (will talk more about the valve body in the next step) replace the Mercedes Transmission 13-Pin Connector Adapter Plug + O-rings. The O-ring plug leaks oil and disrupts the communication between the TCU and the valve body. The O-ring is very easy to replace. Mechanics who are not familiar with Mercedes-Benz transmission suggest replacing the whole transmissions when the root of the problem in the O-ring plug. Replacing the O-ring transmission plug is very easy, anyone can do it if they don’t mind getting dirty. Here are the instructions on how to change the O-ring plug. Once you replace the transmission O-ring plug you will need an OBD-II diagnostic scanner to erase the fault codes.

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4. Replace Valve Body

If you are still having issues with the car going into limp mode and the scanner pointed you in the direction of the valve body then you may want to consider replacing it. The valve body is inside the transmission. The transmission does not need to be removed. Replacing the valve body can per perform with the transmission in place. A new valve body at the dealer can cost between $500 and $1000.

Luckily for you, the transmission does not need to be removed. Which means you can do this repair yourself if you are willing to get under the car. A new valve body at the dealer can cost between $500 and $1000. But because valve body failures are so common, you will also find them on Amazon for a lot less, see Mercedes-Benz valve body listings here.

If your Mercedes-Benz is equipped with the 722.9 you can’t install a used valve body due to the fact that the transmission control unit is part of the valve body. You will either need to get a new valve body which gets expensive considering that it will also require programming. An alternative solution is to try a Mercedes-Benz 7G 722.9 conductor plate repair service. These are independent shops that will take your old 722.9 transmission control module and try to repair it.


https://www.youtube.com/watch?v=8c7pDR83d_E

5. Failed Transmission

Very few Mercedes-Benz cars have had complete transmission failure and require transmission replacement. We see these transmission fail in rare cases when water enters the transmission via the oil cooling lines or the radiator on cars equipped with Valeo radiators. The top part of the radiator on your Mercedes-Benz contains the chamber for the engine coolant/antifreeze while the bottom part contains the chamber for the transmission oil cooling. If cracks develop between the two chambers, coolant will mix with transmission oil and it will destroy the transmission. This has been a well-documented issue for Mercedes-Benz cars equipped with the Valeo radiators.

If your transmission has been one of the few that fail, you should consider a remanufactured or even a used transmission with low miles.

Before you rush into replacing the transmission always read the fault codes from the transmission control unit using a scanner such as the iCarsoft MB II and go from there.
http://www.mercedesmedic.com/mercedes-transmission-problems-limp-mode-no-shifting-troubleshooting-tips/

Gud write up but l bet u 95% of BENZ owner can not do DIY and what u write is for professional mechanic like us

thanks, but I only shared from a devotional site I traveled to. Not my write up.

HyundaiMechco:
Gud write up but l bet u 95% of BENZ owner can not do DIY and what u write is for professional mechanic like us

Kindly include the wheel (abs) speed sensors and the AT filter.

SmartchoiceNGR:
thanks, but I only shared from a devotional site I traveled to. Not my write up.

BABA I HAIL O!

nakoks:
BABA I HAIL O!

Salud sire. How is Engr Friday @Apo?