Mercedes E350 Transmission Problems – Symptoms and Ways to Avoid Them

The Mercedes-Benz E350 is an elegant luxury midsize car designed for the driver's comfort. It features a classy, cutting-edge interior backed by an efficient turbocharged four-cylinder engine. The E350 has a nine-speed automatic transmission to withstand 255 hp and 273 lb-ft of torque.

Mercedes E350 automatic transmissions highlights

• Average lifespan:210,000-240,000 miles
• Reliability Score:High
• Prone to minor issues:No
• Price for repair after failure:$2,000-$2,700
• Price for replacement:$7,000-$8,500
• Availability of parts:Bad
• Common problems:high-mileage problems, very sensitive to fluid quality, require wise use.

3 Common Mercedes E-Class E350 Transmission Problems

• Transmission Leaks Caused By the 13-Pin Connector Failure

The Mercedes-Benz E-Class E350 is a fully automatic vehicle. It's comfortable and easy to drive. The Mercedes E350 comes with a component called the 13-pin connector. This vital part, an electrical connector, of the automatic transmission links all the wires that perform several functions automatically.

Several Mercedes cars, including the E-Class, are prone to failure of this connector. When it does, the problem leads to transmission fluid leaks. This has been a notorious issue with several Mercedes models because undertrained mechanics always confuse it with a faulty valve body. While a defective 13-pin connector will not often damage the valve body, it causes the control module to lose communication with the valve body. As a result, the entire system fails, making a faulty 13-pin connector one of the most notorious Mercedes E350 transmission problems.

• Shifter Stuck in Park Problem

Your car ignites fine, but the shifter won't move to drive. Don't force the shifter. It will only make the problem worse and more expensive to fix. After all, the shifter is connected to the transmission either mechanically or electronically. If there's a faulty component between the shifter and transmission, either mechanical or electrical, no amount of force will move it from P to D. 

When this happens, you will need an expert mechanic to come to your home or your current location to diagnose the Mercedes E350. The mechanic will present their result with the scope of work needed to get it back on the road. A faulty Transmission Control Unit or a broken Transmission Shift Cable are possible causes of the "shifter stuck in Park" problem.

• Solenoid Issues That Send the E350 into Limp Mode

The Mercedes-Benz 9G-Tronic transmission is one of the first 9-speed transmissions in premium luxury vehicles. It was first fitted in the 2013 E-Class E350 Bluetec before making its way into a lot of succeeding Mercedes-Benz vehicles. While the 9G-Tronic is perfect in every way, it has its fair share of problems. The 9G-Tronic is engineered to engage a safe mode whenever there's a critical error in the transmission. This safe mode is called limp mode and is designed to prevent transmission from developing more problems. 

When the 9G-Tronic solenoid fails, the Mercedes E350 automatically disables the affected gear, sending the vehicle into limp mode. Ensure your vehicle reaches a dealership or authorized Mercedes service center when this happens. Do not try to reset the transmission by yourself. The limp mode only engages when a severe problem is affecting the normal functioning of the transmission. 

5 Pretty Common Signs of a Faulty Mercedes E350 Transmission

• The Check Engine Light Is On

One of the easiest ways to tell that your Mercedes-Benz E350 transmission has a problem is by checking the signals on your dashboard. When your gearbox develops an issue, the check engine light will illuminate. Ignoring this signal is like saying, "I love problems." 

Pass by an authorized Mercedes dealership or service center and have a qualified mechanic diagnose your vehicle. Determining the cause and fixing it in time can save you many repair costs. 

• Leaking Transmission Fluid

Transmission fluid keeps the mechanical parts of your gearbox well-lubricated and cool. When this fluid goes below the recommended levels, it causes friction, which causes critical damage to the transmission. To check whether the E350 has a transmission fluid leak problem, check for unfamiliar pools on the ground under the car. 

Ensure you check the transmission fluid levels and condition regularly. A brown and cloudy liquid means it needs to be replaced. When you notice these leaks, contact your dealership for a mobile mechanic to come and run a car diagnostic or take it to the dealership.

• Slipping Transmission

Regular service is one of the most effective ways to ensure your Mercedes is in perfect shape. Low transmission fluid levels or lack of service cause gears to slip. The Mercedes E350 could drop out of gear for a few seconds. It could also experience slow downshifts or upshifts when you accelerate.

While slipping transmission could damage the system if it's not fixed in time, a car that falls in and out of gear is quite dangerous to drive.

• You'll Hear Unfamiliar Sounds

You'll notice unfamiliar sounds when your Mercedes is experiencing a faulty transmission. Furthermore, you will hear whining and buzzing sounds when driving your vehicle. You will also hear grinding noises during shifts. Any unfamiliar grinding or rumbling sounds are a sign that there's an internal problem with your car. 

• There's a Burning Odor from the Front End of Your E350

The smell of a burning odor from your Mercedes is like diagnosing a bad disease in the early stage. It can be treated but could have already caused severe damage. When there's a serious malfunctioning with your vehicle's transmission, and it's overheating, there will be a nasty burning smell from the car's front end. When you notice this, your best option is to take the vehicle to a dealership or service center for diagnosis. 

Keeping the car running with this problem could mean repairing the transmission unit or replacing the whole system. It would be best if you avoid this at all costs. 

4 Tips for Keeping Your Mercedes-Benz E350 Transmission in Top Shape

• Check Fluid Level Regularly

To keep your vehicle's transmission running smoothly, start with the least expensive hack. Check the transmission fluid levels regularly. If the car is seven or eight years old or older, fluid levels can be low due to seepage and other problems. Ensuring that the fluid level is always at its recommended levels ensures the smooth running of the car.

The E350 will engage the limp mode immediately after it senses a low fluid level. The 2022 Mercedes-Benz E350 does not have a dipstick to check the fluid level, but they are sold online for around $20 or less.  

• Read and Clear Fault Codes from the Transmission Control Unit

When your Mercedes-Benz E350 goes into limp mode, it stores a fault code in its computer system. The code related to transmission is stored in the Transmission Control Unit. And with the right OBD II Scanner, anyone can read and understand this code. The E350 could engage the limp mode even for a low battery voltage. 

If the OBD II Scanner reveals something as simple as a faulty battery, you can replace it and clear the code from the TCU. You can borrow an OBD II Scanner from a friend or buy one online, but you need to be sure what works on Mercedes vehicles. If the scanner reveals a transmission problem that needs an expert to fix, your best option is to have it fixed as soon as now. 

• Replace the 13-Pin Connector

You have scanned your car, and what you see points you to a communication problem in the transmission - a problem with the valve body or faulty gear ratios. In most cases, a less-qualified technician will recommend that you replace the valve body altogether. However, replacing the Transmission 13-Pin Connector Adapter Plug and the O-ring could solve the problem. It is always advisable that you have your E350 diagnosed and fixed by a trained and authorized Mercedes technician. 

When the O-Ring is broken or dislodged from its usual position, it causes transmission fluid to leak. And this results in broken communication between the transmission and the valve body. Replacing the O-Ring is an easy task. You can either replace it yourself or have it changed by a technician. Once you have replaced the O-Ring, use an OBD II Scanner to clear the faulty code from the TCU.

• Replacing the Valve Body

If your vehicle is still experiencing transmission problems and your OBD II Scanner pointed you in the direction of the valve body, it could be time to replace it. The valve body is inside the transmission unit, so removing the entire unit is unnecessary. This means you can personally perform this repair hack if you are okay with getting under your E350.    

Final Thoughts

A Mercedes vehicle rarely requires an overhaul, or transmission replacement. To ensure your E-Class E350 never gets to this state, make a habit of visiting your service center at the right time, and conduct an overall diagnostic of your vehicle whenever you sense something is wrong. Make sure your Mercedes E350 transmission problems are diagnosed and fixed in time to keep it performing at its best.