Owners have filed 30 complaints with NHTSA about this car, most about the electrical, engine, and transmission. The 9 checks below target those problems, in the order you would do them at the car.
2021Tick items off on your phone at the car, or print it. Ticks stay on this device.
0/9 checked
2021 Mercedes-Benz GLB: inspection sheet
Before you go, or before you touch the car0/4
Engine off, key in hand0/1
Ask the seller not to warm the car up first0/1
At least 20 minutes, with some highway0/3
These checks are specific to this model year. For tires, body panels, fluids, and the other basics every used car needs, use the general inspection guide.
These years share the 2021's design and most of its parts, so their problems are the ones to look for on this car too.
Worth adding to your 2021 checks
Worth adding to your 2021 checks
Worth adding to your 2021 checks
EPA figures for each version of the 2021 Mercedes-Benz GLB. Use them to confirm you are looking at the version that was advertised, and as a yardstick on the test drive.
| Version | Drive | EPA rating |
|---|---|---|
| 2.0L 4-cyl | 4WD, FWD | 26 mpg |
Owners report these failures starting around the mileages below. A car inside one of these ranges deserves a closer look at that part, or records showing it was already fixed.
Cylinder head failure
29,000–35,000 miles
NHTSA complaints for the 2021 Mercedes-Benz GLB, grouped by the part owners named. Open a row to read what goes wrong.
Electrical faults cause sudden, hard-to-diagnose failures on the road. One car's horn sounds randomly while driving. Another shows a red transmission malfunction warning at highway speed and goes into limp mode. Dealers often cannot reproduce these faults or find stored codes. One car lost its whole dashboard while driving, and the dealer traced it to water entering near the windshield through a possibly clogged drain. Two of the five filings report no failure at all. Those owners describe long waits for parts needed to complete a recall repair.
Complete failure is the main pattern, often with little warning and at mileages as low as 35,000. Owners describe heavy shaking, loss of power, loud noise, a check engine light, and refusal to accelerate. Some cars lock up on the interstate and leave the driver stranded. Shops report metal shavings in the oil, misfires, cylinder head failure, and bearing damage. The usual outcome is a full engine replacement, with high repair estimates and little help from the manufacturer. Losing power at highway speed creates a real crash risk.
Cylinder head failure leads to misfire warnings, rough idle, and sudden power loss. In one case the engine seized again after the dealer replaced the head, and the car sat at the shop for months. Another complaint describes a loud clunk from the left side on each downshift while coming to a stop. The dealer called it normal. A certified used car turned out to have leaking engine mounts, a missing mount screw, worn axles, and brake problems when it went in for routine service.
The front end develops loud clunking, thumping, and cracking noises from the axle area, mainly at low speeds. The noises can appear suddenly and get worse quickly. Some cars still pull left after the dealer replaces the front lower control arms and engine mounts and performs alignments. The driver then has to keep correcting the wheel to stay in the lane. Constant drift raises the risk of an unintended lane departure or loss of control.
A front ball joint can separate from the lower control arm with no warning. In the reported case the drive shaft came loose and the car stopped moving at about 15 mph. A transmission fault warning and loud grinding came first, and the car could not move in forward or reverse. A wheel failure like this at higher speed could cause a crash. A separate complaint describes skids at stops on snow and ice. That car came with summer tires, and the owner was never told.
Excerpts from complaints GLB owners filed with NHTSA, as written. Listen for the same symptoms on your test drive.
I purchased this vehicle in May 28 2025. I certified car. I took in for oil change Nov 17-2025. Found out they had lot of issues., left front bushing arm leaking. Rt engine mount leaking. Bad brakes battery low. Bad tire rt back passage side.front wheel axle and rear wheel axle is bad and screw on the engine mount is missing. Screw and leaking..?and the vehicle needed a alignment.
Filed with NHTSA, January 2026
Complaints for this year next to the average for the other model years, area by area.
The 2021 ranks second for owner complaints among 5 GLB years, about 1.4 times the average of the others. Newer years have had less time to collect complaints, so compare like with like.
Redesigns and mid-cycle updates change what can go wrong.
The 2021 is the second model year of the GLB's first generation (2020 on).
Mercedes-Benz updated the GLB for 2024, so a 2021 does not have those changes.
What changed for 2024 (not on a 2021)
Recall repairs are free at any Mercedes-Benz dealer, but the seller may never have had them done. Check each campaign number against the VIN.
Mercedes-Benz USA, LLC (MBUSA) is recalling certain 2021 GLB250 vehicles. The Electronic Stability Program (ESP) unit may be damaged, which can result in disabled anti-lock brakes (ABS), disabled electronic stability control (ESC), and an electrical short circuit.
Risk: Disabled anti-lock brakes and electronic stability control can increase the risk of a crash or injury. An electrical short circuit increases the risk of a fire.
Fix: Dealers will replace the ESP unit, free of charge. Owner notification letters were mailed October 28, 2022. Owners may contact MBUSA customer service at 1-800-367-6372. MBUSA's number for this recall is 2022090009.
Mercedes-Benz USA, LLC (MBUSA) is recalling certain 2017-2022 CLA-Class, GLA-Class, GLE-Class, GLS-Class, SLC-Class, A-Class, AMG GT-Class, C-Class, E-Class, S-Class, SL-Class, GLC-Class, CLS-Class, GLB-Class, and G-Class vehicles. Please refer to MBUSA's recall report for specific vehicle model details. An error in the communication module's SIM card software can cause a mobile network connection failure, disabling the emergency call (eCall) system.
Risk: A disabled eCall system would prevent a vehicle occupant from contacting the emergency services call center in an emergency, potentially delaying emergency responders and increasing the risk of injury.
Fix: The communication module software will be updated through an Over-the-Air (OTA) update or by a dealer, free of charge. Owner notification letters were mailed July 8, 2022. Owner notification letters will be mailed in phases, on July 8, 2022, May 17, 2024, July 29, 2024, and September 27, 2024. Owners may contact MBUSA customer service at 1-800-367-6372. MBUSA's numbers are for this recall is 2022060005 and 2023110006.
Mercedes-Benz USA, LLC (MBUSA) is recalling certain 2021 GLB 250 vehicles. The level sensor linkage on the rear axle might not have been installed properly, which could affect the headlight leveling function. MBUSA's number for this recall is 2022050011.
Risk: Improperly leveled headlights may project a glare, which can impact other drivers and increase the risk of a crash.
Fix: Dealers will inspect and repair the level sensor linkage, as necessary, free of charge. Owner notification letters were mailed June 10, 2022. Owners may contact MBUSA customer service at 1-800-367-6372.
Mercedes-Benz USA, LLC (MBUSA) is recalling certain 2018-2021 CLA-Class, GLE/GLS-Class, A-Class, C-Class, E-Class, E-Class Coupe/Convertible, GLA/GLB-Class, GLC-Class, and CLS-Class vehicles. Please refer to MBUSA's recall report for specific vehicle model details. The rearview camera may not display the rearview image due to a software error. As such, these vehicles fail to comply with the requirements of Federal Motor Vehicle Safety Standard number 111, "Rear Visibility.".
Risk: An inoperable rearview camera display reduces the driver's rear view, increasing the risk of a crash.
Fix: Dealers will update the rearview camera software, free of charge. Owner notification letters were mailed July 15, 2022. Owners may contact MBUSA customer service at 1-800-367-6372. MBUSA's number for this recall is 2022060007.
Mercedes-Benz USA, LLC. (MBUSA) is recalling certain 2021 GLB 250 vehicles. These vehicles may be equipped with an incorrect front driver's air bag module.
Risk: An incorrect air bag module may not properly restrain an occupant during a crash. In addition, the air bag module could detach from the steering wheel during deployment. Either of these scenarios can increase the risk of injury in the event of a crash.
Fix: Dealers will inspect and replace the front driver's air bag, as necessary, free of charge. Owner notification letters were mailed March 25, 2022. Owners may contact MBUSA customer service at 1-800-367-6372.
Mercedes-Benz USA, LLC (MBUSA) is recalling certain 2021 GLB 250 and AMG GLB 35 vehicles. The driver-side window air bag may not have been mounted correctly to the lower area of the A-pillar. As such, these vehicles fail to comply with the requirements of Federal Motor Vehicle Safety Standard number 226, "Ejection Mitigation.".
Risk: The driver-side window air bag may not function properly during a crash, increasing the risk of injury.
Fix: Dealers will inspect the mounting of the driver-side window air bag and repair it as necessary, free of charge. Owner notification letters were mailed December 2021. Owners may contact MBUSA customer service at 1-800-367-6372.
Mercedes-Benz USA, LLC (MBUSA) is recalling certain 2019-2021 CLA-Class, GLE/GLS-Class, A-Class, E-Class, E-Class Coupe and Convertible, GLA/GLB-Class, GLC-Class, CLS-Class, and AMG GT-Class 4-door Coupe vehicles. Please refer to MBUSA's recall report for specific vehicle model details. The MBUX multimedia system software may cause the display to remain black, or reboot after startup. This could result in the rearview camera image not displaying properly. As such, these vehicles fail to comply with the requirements of Federal Motor Vehicle Safety Standard (FMVSS) number 111, "Rear Visibility.".
Risk: A backup camera that displays a blank image reduces the driver's rear view, increasing the risk of a crash or injury.
Fix: The multimedia system software will be updated by a dealer, or through an over-the-air (OTA) update, free of charge. Owner notification letters were mailed beginning June 28, 2021. Owners may contact MBUSA customer service at 1-800-367-6373. MBUSA's number for this recall is 2021050012.
Mercedes-Benz USA, LLC (MBUSA) is recalling certain 2021 GLB35 AMG, and 2020-2021 GLB250 vehicles. The side spoilers on the tailgate might not have been installed correctly, allowing them to detach.
Risk: Detached spoilers can create a road hazard, increasing the risk of a crash or injury.
Fix: MBUSA will notify owners, and dealers will inspect and, if necessary, replace the side spoilers, free of charge. Owner letters were mailed July 2, 2021. Owners may contact MBUSA customer service at 1-800-367-6372. MBUSA's number for this recall is 2021050009.
Mercedes-Benz USA, LLC (MBUSA) is recalling certain 2020-2021 GLB250 vehicles. The wheel arch covers on the front fenders might not have been installed correctly, allow them to detach.
Risk: Detached wheel arch covers can create a road hazard, increasing the risk of a crash or injury.
Fix: MBUSA will notify owners, and dealers will check the installation of the front wheel arch covers and correct them as necessary, free of charge. Owner letters were mailed May 21, 2021. Owners may contact MBUSA customer service at 1-800-367-6372. MBUSA's number for this recall is 2021040015.
Mercedes-Benz USA, LLC (MBUSA) is recalling certain 2016 - 2021 CLA-Class, GLA-Class, GLE-Class, GLS-Class, SLC-Class, A-Class, GT-Class, C-Class, E-Class, S-Class, CLS-Class, SL-Class, B-Class, GLB-Class, GLC-Class, and G-Class vehicles. Please refer to the Part 573 report for specific vehicle model details. The software design of the communication module may fail to communicate the correct vehicle location for the emergency call system (eCall) in the event of a crash.
Risk: Failure of the eCall system may result in emergency responders being dispatched to the wrong location, increasing the risk of injury following a crash.
Fix: MBUSA will notify owners, and the communication module software will be updated by a dealer, or through an over-the-air (OTA) update, free of charge. The recall began March 12, 2021. Owners may contact MBUSA customer service at 1-877-762-8267. MBUSA's number for this recall is 2021020025.
Cars shoppers compare with the Mercedes-Benz GLB, with their own 2021 checklists.
2021 owner complaints, side by side
