2019 Mercedes-Benz GLC 300

On January 8, 2021, after ongoing review with Mercedes Benz, the National Highway Traffic Safety Administration (NHTSA) Office of Defects Investigation (ODI) opened PE21-001 to assess allegations of front roof panel detachments while driving at highway speeds in certain 2015 Mercedes-Benz (Mercedes) C-Class vehicles.The subject front roof panel is a stationary panel composed of polycarbonate and is attached to the vehicle via adhesive at the time of manufacture. The panel is found on subject vehicles equipped with panoramic sunroofs. Over time, the subject panels may exhibit cosmetic degradation leading to replacement of the panel, a procedure which entails: removal of the old panel and adhesive, site preparation, and installation of a replacement panel with new adhesive.The consumer complaints that prompted the opening of PE21-001 all described detachments of front roof panels that had been replaced after the vehicle was put into service.Mercedes' internal investigation identified a broader scope of affected vehicles (2014-2020 CLA, GLA, C, S, GLC, and GLE class) and found the following potential service procedure- related causes of front roof panel detachments:- Improper surface pretreatments such as the use of the wrong primer or cleaner or scoring of the surface; or - Use of the incorrect adhesive.These conditions lead to a front roof panel bond that, even if sound at the time of repair, cannot maintain its strength over time and environmental exposure.Mercedes updated its service and parts ordering systems to reinforce the proper use of specified kits and procedures via webinars, shop foreman meetings, and explicit reference to the risks incurred by diverging from the repair procedures. Mercedes is also furnishing parts ordering assistance, and will hold dealerships accountable for improper repairs.ODI's analysis of the ten complaints it has received from the public (VOQ's) and MBUSA's complaint data submitted in response to the information request letter for PE21-001 identified a total of 57 non-duplicative reports alleging incidents in which the front roof panel detached from the vehicle while in motion. Included within the 57 reports are incidents where consumers state the panel detached ...and flew off into traffic.On March 19, 2021, Mercedes notified NHTSA that it would recall subject vehicles with front roof panels known to have been replaced after the original sale of the vehicle. In total, the recall (designated as Recall 21V197) covers 15,099 vehicles that were ever registered in the United States. Based on Recall 21V197 and the remedy implemented by Mercedes, further investigation does not appear to be warranted at this time.Accordingly, this investigation is closed.The ODI complaints cited above can be viewed at www.nhtsa.gov under the following ODI identification numbers: 11376425, 11352686, 11351629, 11349158, 11341541, 11337594, 11324100, 11311591, 11222127, 11404183

vehicle: 2019 Mercedes-Benz GLC 300 Component Involved: Integrated Transmission Control Module (TCM) / Mechatronic Unit Active Diagnostic Code: P073E (Unable to Engage Reverse) Description of Event: While attempting to back out of a driveway, the vehicle experienced a sudden, catastrophic electronic transmission failure. Without any warning or prior symptoms, the vehicle abruptly kicked itself out of gear and dropped into Neutral. The vehicle completely lost all propulsion and ability to move backward or forward, rendering it entirely disabled. This failure occurred directly in the path of oncoming traffic, creating an immediate, life-threatening safety hazard for myself, my passengers, and other drivers. Due to the complete loss of gear engagement, we were trapped in a highly dangerous and vulnerable position. A subsequent scan of the vehicle’s onboard computer revealed active diagnostic code P073E (Unable to Engage Reverse), indicating a documented internal failure within the 9G-Tronic mechatronic/transmission control unit. The vehicle is currently completely unsafe to operate and has been parked in a residential garage to prevent a severe collision. Given that this is a sudden component defect that results in an immediate loss of vehicle control rather than standard wear-and-tear, this issue represents a critical manufacturing safety hazard that requires immediate corporate intervention.

NHTSA ID

11764849

Incident

Sep 12, 2026

On April 16, 2026, within minutes of being released from a certified dealership, my 2019 Mercedes-Benz GLC 300 suffered a sudden and total loss of propulsion while traveling at high speed on the Belt Parkway (NY). Despite depressing the accelerator, the vehicle failed to maintain speed and stalled in active traffic. This created an immediate life-safety hazard, forcing me to navigate across multiple lanes without engine power to avoid a high-speed rear-end collision. The vehicle was released to me by Mercedes-Benz of Brooklyn on April 16, 2026, following a repair for which I paid $2,134.94. The dealership diagnosed the issue as a wiring harness/sensor fault and formally certified the vehicle as "Found OK" and safe for operation. The catastrophic failure occurred only 22 minutes after I departed the dealership lot. The vehicle had to be towed back to the facility immediately. Upon the vehicle being towed back on April 16, the dealership admitted via recorded voicemail that the initial $2,134.94 repair was a misdiagnosis. They subsequently issued a new diagnosis for a "Valve Body" failure and a new quote of $6,424. The dealership's Service Director has since admitted the vehicle suffers from concurrent transmission and engine failures, rendering the car a liability. This represents a critical failure of the powertrain and electronic control systems. Releasing a vehicle that suffers a total power loss on a highway immediately after a "certified" repair is gross negligence. I am reporting this to NHTSA as a catastrophic failure of a safety-critical component (Transmission/Valve Body) that resulted in a "dead-stick" situation on a major New York thoroughfare, posing a severe risk to myself and other motorists. The vehicle remains at the dealership. Mercedes-Benz USA has offered only a $2,000 "goodwill credit," which does not address the safety defects or the initial misdiagnosis. No recall has been initiated for this batch.

NHTSA ID

11736351

Incident

Apr 16, 2026

The contact owns a 2019 Mercedes-Benz GLC300. The contact stated that while driving 65 MPH on the interstate, the sunroof suddenly shattered into pieces and flew off the vehicle. The vehicle was driven to a dealer but was not repaired. The manufacturer was notified of the failure. The failure mileage was 106,706.

NHTSA ID

11729435

Incident

Apr 5, 2026

Mileage

106,706 mi

I have a MC Benz 300 GLC with $50,000 miles. I was having heating issues so took it to the dealership, which basically advised of the issue describer below, which would cost $14k to repair. Contaminated coolant in Mercedes-Benz GLC 300 models often results from the internal failure of a "desiccant bag" inside the coolant expansion tank, which disintegrates, releasing material that clogs the heater core. Symptoms include black residue in the tank, reduced cabin heat, and engine overheating. Key actions include replacing the expansion tank (reservoir) and flushing the entire system.

NHTSA ID

11728476

Incident

Mar 31, 2026

A message that passenger air bag is damaged/will not deploy appears. Passenger seat belt gets stuck and cannot be opened. Check engine light on-pvc valve issue most likely.

NHTSA ID

11726943

Incident

May 1, 2025

SUNROOF EXPLODED AND SHATTERED. I HEARD IT WHILE DRIVING AND HELD ON TIGHTLY TO THE STEERING WHEEL BEFORE I REALIZED WHAT IT WAS. THE DEALER AND MY AUTO INSURANCE HAVE BEEN CALLED, NEITHER PICKED UP, AND I LEFT EACH A VOICE MAIL MESSAGE. NO WARNING LAMPS, MESSAGES OR OTHER SYMPTOMS OF THE PROBLEM OCCURRED.

NHTSA ID

11721035

Incident

Feb 27, 2026

My sunroof just exploded while driving on the highway without any impact or warning. It was a clear sunny day. There wasn't a vehicle in front of me. Nothing fell on my windshield nor sunroof. The sudden explosion and shattering of the glass was extremely startling. I had a mesh underneath the sunroof that contained some of the shattered glass so it did not fall on me while I was driving. I'm so thankful there wasn't a car behind me for the glass debris to fall on. Mercedes USA was not helpful, unresponsive for many weeks. They eventually declined repair coverage due to out of warranty, not manufacture defect nor safety issue.

NHTSA ID

11716844

Incident

Dec 30, 2025

I was driving on a street 5mph and all of a sudden my car surged and led me to curb where i knocked hit a steer din and it veered onto someone’s lawn and hit a huge planter and stopped . Air bags were deployed . I had no control over the car . EDR was preformed and I’m sure it was a throttle surge issue and cause unintended acceleration . The edr shows I was going 5 miles an hour but then says pedal was pushed to 100%. While traveling at approximately 4–5 mph during a low-speed maneuver, with light accelerator input, the vehicle unexpectedly surged forward. I did not intend to accelerate. The vehicle rapidly increased speed, left the roadway, struck a street sign and a planter, and the airbags deployed. Event Data Recorder (EDR) data retrieved by the insurer (Mercury Insurance) shows the vehicle traveling at low speed immediately prior to the event, followed by a recorded 100% accelerator pedal position. This data does not reflect my driving intent and appears inconsistent with the low-speed conditions. The EDR documentation notes that accelerator pedal position is sampled asynchronously and reflects values transmitted to the SRS Control Module, not continuous pedal input or driver intent. No brake input was recorded prior to the impact. The sudden acceleration occurred too quickly to react. Mercedes-Benz inspected the vehicle and released only the EDR data, declining to provide further clarification regarding throttle control logic, pedal sensor correlation, or torque command behavior. I am reporting this incident due to concern that low-speed throttle control behavior, software logic, or transmission engagement may result in unintended acceleration without corresponding driver intent, posing a safety risk during parking-lot or low-speed driving conditions.

NHTSA ID

11714225

Incident

Aug 11, 2025

Complaint During part of the steering movement, it feels heavier or more difficult to steer in the same spot every time. OR Rattling, humming, dry sliding/gravel noise from the electric steering system when steering (see attachment). Complaint does not impact the ability to safely steer or control the vehicle. Cause Ball screw drive (KGT) of electric steering damaged by: 1. External force due to: ‑ Hitting the curb/posts with the front wheels. ‑ Driving over obstacles (e.g. pothole/ threshold/ speed bump/ gully) at an inappropriate speed. 2. Corrosion/ water ingress through a damaged boot (see attachment). ‑ Cracks (1) ‑ High pressure cleaner (2) ‑ Animal bite (3) See various examples listed in the attachments for examples of outside influence. Remedy Remove boot clamps closest to steering gear housing on both left and right (as seen in "Steering Rack Boot Clamp Location"). Pull back boot and inspect for rust, broken end stops, water, or any other anomalies. Replace electric steering. Note: Steering gears replaced due to outside influence or damage must not be claimed under warranty!

Complaint Tailgate opens unintentionally. Cause Accidental or unnoticed activation of the button to open the tailgate on the vehicle key. EXAMPLE: when stored in trouser pocket, handbag etc. Remedy As of the 6th generation, the vehicle key can be recoded so that the tailgate no longer opens as a result of a long press on the button, but by double‑clicking on the button instead. This reduces the likelihood of the button being activated accidentally or unintentionally. The recoding can be carried out as follows: 1. Add SA Code O19 into VeDoc (O for Oscar, not "zero") • an XSS ticket may be necessary to add the SA code 2. Perform SCN coding of EIS N73 control unit 3. Deactivate the vehicle key (a successful deactivation is indicated by the LED lighting up 2x briefly and then 1x for a long period). 4. Place the vehicle key in the storage compartment on the key symbol and turn on the ignition. IMPORTANT: all other vehicle keys must be outside the recognition range of the vehicle when doing this! Perform steps 3 and 4 successively for all vehicle keys. Notes: 6th, 7th and 8th generation keys can be deactivated as follows: Up to modification year 22/1 by double clicking the "Lock button" As of modification year 22/1, by press and holding the “Lock button", then double‑click the “Unlock button" at the same time. On model series 167, the storage compartment with the key symbol is located in the armrest. The SCN coding from the EZS is only transferred correctly to the vehicle key under the following conditions: Only one vehicle key is located in the vehicle, this key has been deactivated and it is positioned on the marking in the storage compartment for the data transfer. The costs for this adaptation are to be borne by the customer. For the newer BR 174, 178, 244, 248, 520, and 540, a software update must be initiated, as there is no way to perform SCN coding.

Dear Mercedes-Benz Owner: In our continuing efforts to ensure the proper performance of Mercedes-Benz products and to enhance the satisfaction of our customers, Mercedes-Benz USA is extending the warranty coverage for the Diagnostic Module for Tank Leakage Detection ("DMTL") on your vehicle from the original New Vehicle Limited Warranty of 4 years / 50,000 miles to 15 years/150,000 miles (whichever occurs first). This applies to the vehicle regardless of ownership. Why the Warranty extension? On certain Model Year 2018 - 2024 A / C / CLA / CLS / E / G / GLA / GLB / GLC / GLE / GLS / GT / S / SL Mercedes-Benz vehicles, under certain circumstances, the DMTL may trigger erroneous Diagnostic Trouble Code ("DTC") entries that may result in the illumination of the Check Engine Malfunction Indicator Lamp ("MIL"). Any repairs under this warranty extension must be performed by an authorized Mercedes-Benz dealership. • If your preferred authorized Mercedes-Benz dealership performs a diagnosis and confirms that your vehicle has the issue, the repair will be covered under this extended warranty and performed at no cost to you. • This extended warranty does not apply to any other components or conditions beyond the ones mentioned above, and standard warranty terms apply, including the exclusions with respect to extra expenses, as identified in the Service and Warranty Information booklet.

Complaint 1. General Diagnostic Tips 2. One or More PARK Sensor Activations 3. Red Ring Around Vehicle 4. "Active Parking and Parking Assist Inoperative" on Instrument Cluster 5. Cameras 6. Other Park Topics. Cause Various root causes Remedy See attached diagnostic guide.

Complaint Clanking noise from the area of the speakers in the doors. Cause Under analysis. Remedy To narrow down the cause, first of all remove the door trim. • If the noise continues to occur even with the door trim removed, then continue the diagnosis working towards the speaker and if necessary, create a TIPS case with an informative video as an attachment. Information: Please refer to this document in the warranty claim and, after completing diagnosis, select the damage code corresponding to the component part that caused the problem. • If the noise stops when the door trim is removed, please proceed in accordance with LI72.10-P-067691. Information: In this case, do not use a damage code for the speakers in the warranty claim!

Complaint A popup is seen on the HU with the message "data connection temporarily not available". Potentially affected functionalities in NTG4.5, NTG5 1.Weather 2.Local Search 3.IP Radio 4.Send2Car 5.Speech Detection Service 6.Navigation 7.iHeartRadio 8.Traffic Cams Cause MB Apps is sundowned for all vehicles with NTG4.5 and NTG5 Head Unit Variant. Remedy No support available for NTG4.5 and NTG5 Head Unit Variants for MB App related topics. Note: Please do not create TIPS. Please do not replace any components. HU/Hermes SW update / SCN coding will not fix the issue.