We accepted delivery of our brand new vehicle in May 2021 from the dealer. In July 2021, the vehicle became completely disabled due to failure of the 48 volt battery. In October 2021, the dealer replaced 48 volt battery failed again causing the vehicle to become completely disabled. In December 2023, our 3rd replacement 48 volt battery failed. Each time the vehicle is out of service for a week…
2021 Mercedes-Benz GLS-Class electrical problems
severe 14 complaints filed with NHTSA · avg repair $850 · see electrical across all vehicles →
Complaints
14
Recalls
0
Avg fix
$850
2fires
The failure pattern owners describe
Fourteen complaints center on the 48-volt battery system that powers the vehicle's mild-hybrid functionality. The most serious incidents involve fire: one owner reported flames and smoke erupting from under the passenger seat during routine driving, causing total loss and potential injury; Mercedes had issued recalls in April 2022 and March 2024 specifically for a loose ground wire under that seat.
More commonly, owners describe repeated battery failures that shut the engine off mid-drive—at 75 mph, in intersections, and while accelerating—forcing dangerous merges or stops. One owner had three battery replacements over 2.5 years; another with 31,000 miles has spent 30 combined days at a dealership without resolution and reports the vehicle still fails after dealer attempts to fix it. Diagnostic codes B183214, B183216, B183217, and B183371 relate to the 48V battery and its management system.
A separate electrical failure involves the instrument cluster display blacking out for 3–4 hours at a time, making the speedometer, fuel gauge, and warning lights invisible—a hazard during operation. One owner's dealership stated after four visits that no solution exists.
Dealerships have offered software updates and battery replacement, but owners consistently report failures persist despite these interventions. Mercedes corporate offered one owner a $200 service credit and $3,000 toward a new vehicle, acknowledging no defects.
Same Mercedes-Benz GLS-Class electrical reports on nearby years: 2020
Failure modes owners describe
48V Battery Failure with Engine Shutdown
The 48-volt mild-hybrid battery fails during operation or during startup, causing complete vehicle shutdown, inability to accelerate, or total loss of propulsion. Owners report the vehicle becomes undriveable or dies mid-drive. Multiple owners experienced repeated failures requiring battery replacement or dealership intervention.
When: Various mileages; first owner reported 31k miles; incidents reported from 2021-2025; some failures occur after sitting overnight, others while driving or accelerating
Symptoms owners cite: Vehicle shuts off completely while driving or at idle; Engine fails to start or start with difficulty; Vehicle unable to accelerate beyond 30-50 mph; 48V battery warning displayed on dashboard; Check engine light illuminates; Multiple warning progression: orange 48V battery malfunction warning, then red 12V battery malfunction; Vehicle restricts speed or commands immediate stop
Codes mentioned: B183214, B183216, B183217, B183371, 48-volt battery failure, Check engine light
Repairs/costs cited: Dealership typically replaced 48V battery; owners report repeated replacement (3 replacements in one case over ~2.5 years); dealership performed software updates; some dealerships stated no defect found despite symptoms; one owner reports dealer concluded no solution possible after 4 visits
Recalls/TSBs owners mention: Mercedes issued recalls in April 2022 and March 2024 for loose ground wire under passenger seat causing fire risk; Mercedes USA offered 200 service credit and 3,000 off new vehicle to one owner; owners report manufacturer stated not aware of defects; some owners have open PTSS cases with Mercedes USA
48V Battery Fire/Smoke Hazard
The 48-volt battery system or associated wiring under the passenger seat ignites, creating a fire with flames and smoke that spreads rapidly. This is the most severe manifestation of the electrical system failure and represents an imminent safety hazard. Owners report that the fire occurred while the vehicle was in normal use, and in one case the vehicle became a total loss.
When: One incident in routine driving at unspecified mileage; one incident with smoke damage but vehicle not fully documented
Symptoms owners cite: Fire flames visible under passenger seat; Smoke inside vehicle; Rapid fire spread; Vehicle becomes total loss or severe damage; Risk of entrapment and burn injury
Codes mentioned: 48V loose ground wire (recall root cause)
Repairs/costs cited: One vehicle became complete total loss and burned; fire investigation scheduled; no repair possible once fire occurred
Recalls/TSBs owners mention: Recalls issued April 2022 and March 2024 for loose 48V ground wire under passenger seat causing fire risk; joint fire investigation with insurance company scheduled; Mercedes delayed investigation scheduling
Instrument Cluster Display Blackout
The instrument cluster display blacks out intermittently, disabling the speedometer, head-up display, and warning indicators. The display remains dark for 3-4 hours and only resets after 1-2 days of non-use. This creates a serious safety risk because the driver loses critical information required for safe operation.
When: Incidents occurred 5/13/22, 6/17/22, 6/13/23, and recurring through 2024; dealership unable to resolve after 4 visits
Symptoms owners cite: Instrument cluster display blacks out completely; Speedometer becomes invisible; Head-up display turns off; Warning lights not visible; Fuel gauge information unavailable; Display remains dark for 3-4 hours; Issue recurs sporadically
Repairs/costs cited: Owner visited dealership 4 times; final visit (7/16/24) dealership concluded no further solution possible to fix the issue
Multimedia/Infotainment System Shutdown
The multimedia system abruptly shuts off while the vehicle is operating, occurring simultaneously with battery management warnings. This is a secondary electrical system failure tied to the 48V battery malfunction cascade.
When: Occurs during 48V battery failure events
Symptoms owners cite: Multimedia system suddenly shuts off while driving
Codes mentioned: Related to 48V battery and management system errors
Software-Related Startup Issues
The vehicle experiences startup failures or delays attributed to software issues in the 48V battery management system. Owners report dealership performed software updates to address starting problems, though some failures recurred.
When: Incidents reported in 2022
Symptoms owners cite: Vehicle will not start; Vehicle turns on by itself unexpectedly; Startup delays
Codes mentioned: 48V battery system
Repairs/costs cited: Dealership performed software update as repair; one owner reports issue persisted after update
Recalls/TSBs owners mention: Dealership cited delayed software update as reason for non-start condition
Synthesized from 14 NHTSA owner complaints — unverified consumer allegations, summarized for patterns. The verbatim filings appear below.
What owners are reporting 8 most recent
Vehicle has just over 31k miles. ON multiple occasions, the vehicle randomly shuts off and displays a 48 volt battery error on the screen followed by a check engine light. This has happened in the middle of a busy intersection and at 75mph on the interstate. Each time it does this, I have taken it to a Mercedes dealer for repair/troubleshooting. THey perform the Mercedes required steps to repair…
Incident 1: May 2022 Vehicle was sitting in driveway overnight and would not start in the morning. Had a 48V battery warning on. Towed to dealership. Said it was a delay software update. Incident 2: August 2022 Was driving 35mpg down the road where a warning sign comes up. Then shortly after the car slows down to around 15mph and would not speed up anymore. Towed to dealership. Dealership did…
Car would not start, 48 volt system failure
Car shut off while driving. Would not restart. 48 volt battery failure, needed software update
Car turned on by itself, then 2 days later would not start. 48v battery system needed software update
Vehicle would not start on 3 separate occasions. The instrument panel indicated it was the 48v battery. Had it towed to Mercedes dealership to have 48v battery replaced.
1. Unknown, smoke started coming from under the passenger side seat, car is a complete loss. 2. Smoke damaged my lungs, there was a large amount of exploding glass, and it could have led to a structure fire. 3. Not applicable 4. In process, but it was recalled for this issue 5. No
Had electrical trouble with your 2021 Mercedes-Benz GLS-Class?
File a complaint with NHTSA → It's free, official, and how every report above got here — owner filings are the federal safety record this page is built on.
Common questions
How serious is the electrical problem on the 2021 Mercedes-Benz GLS-Class?
It's a meaningful issue. 14 complaints have been filed and the failure mode causes operational problems for owners. Repairs average $850.
At what mileage does the electrical typically fail?
Mileage data is limited for this issue. Owners report failures across a wide range, suggesting cause is more about driving conditions and maintenance than mileage alone.
What does it cost to fix?
Independent shops typically charge around $850 for electrical repairs on this vehicle. Dealer pricing tends to run 20-40% higher. The exact figure depends on the specific failure mode, parts availability, and your local labor rates. If you're outside factory warranty, an extended service contract often covers this category.
Are there any recalls related to electrical?
No active recalls currently cover electrical issues on this vehicle. The complaints filed represent owner-reported failures that haven't risen to the level of a manufacturer-issued recall — but they're still worth knowing about before you buy or budget for repairs.
Related
Complaint and recall data sourced from the National Highway Traffic Safety Administration (NHTSA)
public records database. Verify the raw federal record at
nhtsa.gov/vehicle/2021/Mercedes-Benz/GLS-Class.
Severity ratings are derived from reported crashes, fires, injuries, and fatalities. Repair cost estimates are
independent-shop national averages and may differ in your area. Some links on this page are affiliate links.