Mercedes-Benz · Known Issues
2020 Mercedes-Benz GLC Problems: 12 Known Issues
2020 model year · 4,200+ owner reports · Updated September 2026
2020 · All trims · All engines
Choose the year and equipment for your written issues and visual request.
2020 model year · 4,200+ owner reports · Updated September 2026
2020 · All trims · All engines
Choose the year and equipment for your written issues and visual request.
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According to Au7o's analysis of 4,200+ owner reports, the 2020 Mercedes-Benz GLC has 12 documented known issues, with 4 rated critical. The most serious are Air Suspension Compressor Failure ($600-$2,000 repair), 48V Mild-Hybrid (EQ Boost) Integrated Starter-Generator Failure ($1,000-$7,000 repair), SCR / AdBlue System Plausibility Failure Triggering a No-Restart Countdown (OM651 Diesel) ($400-$3,000 repair) and Active Brake Assist and 360-Degree Camera False Activations (Phantom Braking) ($0-$1,500 repair). The most commonly reported issue is 9G-Tronic Harsh Shifting with 2,000 owner reports. Across all issues with published estimates, repair costs range from $120 to $7,000. DIY maintenance guides at au7o.io.
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According to Au7o's analysis of 4,200+ owner reports, the 2020 Mercedes-Benz GLC has 12 documented issues. The most frequently reported are: Air Suspension Compressor Failure, 48V Mild-Hybrid (EQ Boost) Integrated Starter-Generator Failure, SCR / AdBlue System Plausibility Failure Triggering a No-Restart Countdown (OM651 Diesel). Of these, 4 are rated critical and should be addressed promptly.
The 2020 Mercedes-Benz GLC has 12 known issues documented across 4,200+ owner reports. 4 issues are rated critical: Air Suspension Compressor Failure and 48V Mild-Hybrid (EQ Boost) Integrated Starter-Generator Failure and SCR / AdBlue System Plausibility Failure Triggering a No-Restart Countdown (OM651 Diesel) and Active Brake Assist and 360-Degree Camera False Activations (Phantom Braking). Prospective buyers should inspect for these issues and factor potential repair costs into their purchase decision. Regular maintenance following the manufacturer's schedule helps prevent many common problems.
Repair costs for known Mercedes-Benz GLC issues range from $0 to $7,000, depending on the specific problem and whether you choose DIY or professional repair. The most critical issue, Air Suspension Compressor Failure, typically costs $600-$2,000 to repair. Au7o provides step-by-step DIY maintenance guides that can help reduce repair costs.
GLC models equipped with optional AIRMATIC air suspension experience premature compressor failure. The compressor overheats from compensating for minor air spring leaks and eventually burns out, leaving the vehicle in a lowered position. Repairs typically run $600-$2,000. Severity: high.
GLC 300 models with the M264 engine use a 48-volt mild-hybrid system with an Integrated Starter-Generator (ISG) mounted between the engine and transmission, fed by a small lithium-ion battery. The ISG, its 48V battery, or a loose/overheating 48V ground connection can fail, trigge… Repairs typically run $1,000-$7,000. Severity: high.
European-market GLC 220d and 250d models with the OM651 diesel run an SCR aftertreatment system that will refuse to allow further engine starts once the control unit loses confidence in NOx conversion. Owners and technicians report the dash showing "Engine start not possible in x… Repairs typically run $400-$3,000. Severity: high.
GLC owners report the driver-assistance suite reacting to obstacles that are not there. The "checking surroundings" screen pops up several times a week with sections of the car outlined in red and nothing nearby, and — more seriously — Active Brake Assist has applied the brakes w… Repairs typically run $0-$1,500. Severity: high.
The 9G-Tronic (725.0) nine-speed automatic transmission exhibits harsh downshifts and jerky low-speed behavior, particularly the 1-2 and 2-1 shifts. The transmission software struggles with the many gear ratios at parking lot speeds. Repairs typically run $150-$2,500. Severity: medium.
On the X253 GLC 300 the vacuum-operated turbo wastegate actuator uses a rubber diaphragm that hardens and tears after repeated heat cycling. Once it splits, the actuator can no longer hold vacuum, the wastegate hangs open, and the engine never builds commanded boost. The ECU logs… Repairs typically run $350-$900. Severity: medium.
GLC headlamp assemblies collect water inside the lens. Mercedes recalled a narrow build window — 129 units of 2021 GLC 300, GLC 300 4MATIC, AMG GLC 43 and AMG GLC 63/63 S built May-June 2021 — because the sealing plugs in the headlamp connector housing were not properly installed… Repairs typically run $0-$2,200. Severity: medium.
X253 GLC owners report a heavy metallic clunk from the front end, most obvious over expansion joints and while turning, along with a squeak from the front suspension at low speed. The cause is the rubber bushings in the front lower spring control arm and the hydraulic (fluid-fill… Repairs typically run $600-$1,800. Severity: medium.
On the M274/M264 2.0L turbo engines used in the GLC, the intake camshaft adjuster relies on an internal locking pin that wears over time. Without oil pressure at cold start, the adjuster fails to lock in its default position, producing a distinct metallic rattle for 2-4 seconds o… Repairs typically run $800-$2,500. Severity: medium.
The panoramic sunroof develops creaking and rattling noises over bumps and temperature changes. The glass panel expands and contracts differently than the metal frame, creating friction-induced squeaks especially in cold weather. Repairs typically run $0-$500. Severity: low.
The MBUX infotainment system freezes, reboots, or displays a black screen. Bluetooth connections drop, Apple CarPlay/Android Auto disconnects randomly, and the voice assistant becomes unresponsive. Repairs typically run $0-$2,000. Severity: low.
The GLC power tailgate uses a motorised spindle drive on one side and a gas-charged support strut on the other. When the gas charge leaks out of the passive strut, the tailgate no longer has enough force to stay up: owners describe the boot opening normally and then immediately c… Repairs typically run $120-$450. Severity: low.
Content on this page was compiled with AI assistance using NHTSA complaints, TSBs, owner reports, and public automotive data. While we strive for accuracy, this information may contain errors. Always verify repair procedures and specifications with your vehicle's service manual or a qualified mechanic.