SRNH

Friday while driving my CPO '22 GLB250 with 20K miles and entering a rotary the transmission froze in 3rd gear, tried the paddles and more gas to no avail. Noticed the displayed "Transmission Malfunction" error message. I literally "Limped" home some 7 miles stuck in 3rd and we have some hills, down to 15 MPH at times, thank goodness no tricky on ramps requiring acceleration, very unsafe.

Not until I read this article Transmission Malfunction For Mercedes (Here Is How To Solve) (weldingtroop.com) did I become aware of the error message "Transmission Malfunction" and Limp Mode + possible causes. When you're driving and don't have the leisure to research "things" that can go wrong it's a whole different experience. Once home pulling into the garage, I immediately shut it down and called Roadside Assistance. I told them about the "Transmission Malfunction" error message, they asked if it was stuck in Neutral, then asked if I could drive it, hmmmmm.....so with them on the phone I restarted, put in reverse and then in drive (no issues) to situate it for flat-bed pick-up. Not having used Roadside Assistance I learned they will tow a disabled vehicle at no cost to the closest MB Dealer, or, you may choose another dealer at a cost to you of $4.00 a mile after the first 50 miles and of course I opted for the closest dealer. Received a call from the dealer today around 11AM and they said several Fault Codes pointed to a faulty Automatic Transmission Valve Body. The service manager said they ordered the replacement part which would take 3 to 5 days to receive, and then would schedule that work, as an FYI that dealer is 73 miles from my home.

I could not imagine being on a trip with a dog and this occurring, although we do have Rental Car Coverage in our regular vehicle insurance policy.

SRNH

After a week at the dealership, we finally picked-up the GLB, all work covered under warranty, my wife drove it home while I followed in the ML350BT, no problems encountered however I was a bit surprised at the SERVICE INVOICE entry below.

"CUSTOMER STATES AS HE WAS SLOWING DOWN COINC INTO A ROTARY A MESSAGE FOR TRANSMISSION MALFUNCTION
CAME UP AND VEHICLE WOULD NOT SHIFT OUT OF 3RD GEAR.

PERFORMED TEST DRIVE. COULD NOT DUPLICATE. CONNECTED CHARGER AND SDS. F0UND C0DE: P077600. ATEMPTED To
PROCESS FAULT CODE - CODE PROHPTS TO CONTINUE DIAG IN VCS, CODE ITSELF IS IN VGS. FOLLOWED IPR BASED ON COMPLAINT.

RESULT: REPLACE VALVE BODY. REMOVED UNDERPANELS, DRAINED OIL.REMOVED CHARGE AIR PIPE, FAN SHROUD, DETACHED COOLER. REMOVED OIL PAN, REPLACED VALVE BODY, REPLACED ALL 4 FILTERS. INSTALLED IN REVERSE ORDER.

DURING INSTALATION: HAD ISSUES W CONNECTOR, CLEANED OFF OLD OIL. FILLED AND SET TRANSMISSION FLUID LEVEL. HAD ISSUES WITH ULTRASONIC
TOOL. PERFORMED FULL ADAPTATIONS AND IST OF DKG, MULTIPLEXER CONNEDTION FAILED, HAD To RESTART. PERFORMED TEST DRIVE. IF ISSUE WILL REOCCURE- RECOMMENDED TO COME BACK FOR
FURTHER DIAG."

ILoveNY

I had a similar issue on my GLB

SRNH

I am surprised how the jerkiness of the shift changes has ceased. The acceleration is smooth and steady, so far so good but in the back of my mind I'm not using this vehicle for any long trips until I feel more confident something else isn't going to pop-up. The primary repair consisted of replacing PN # 247-370-18-02-87 - Remanufactured Controller Unit, Electroh + changing all the transmission filters, replacing the transmission fluid and pan gasket. Since purchasing this vehicle, I just thought the shifting feel was normal, not so I am finding.