Mercedes-Benz AMG GLC 63 S E Performance
Two-litre turbo with 350 kW, electrically assisted exhaust turbocharger, 150 kW electric motor on the rear axle ā 500 kW system output. Barely audible at idle, often running on electricity alone. At full throttle a hoarse four-cylinder howl that doesn't satisfy the ears no matter how fast the needle rises. The electric turbo eliminates every trace of turbo lag; boost is immediate. 6.1 kWh battery in immersion cooling (14 litres of coolant flow directly through the cells). On paper a masterpiece: 2,165 kg in 3.4 seconds to 100, 280 km/h top speed. In practice a dilemma ā the target audience wanted V8 sound and emotion, got 2.1 tonnes of high-voltage complexity. AMG chief Schiebe publicly admitted: customers were lost. Consequence: the CLE 63 gets a V8 back, the C63 successor will be the C53 with an inline-six. Maintenance is AMG-level: oil every 10,000 km (MB229.51, 7 litres), HV system only in certified workshops.
GLC 63 E Performance: Hybrid Hammer
350 kW system output in the SUV ā the electric motor on the rear axle delivers instant thrust that no turbocharged V8 can match. Absurdly fast in a straight line; the weight makes itself felt only in tight corners. Drift mode in an SUV remains an experience.
Engine Weaknesses 12
Affected MY 2022ā2023 AMG C43: incorrectly-length gearbox wiring harness fitted, can cause loss of drive.
Symptoms: Warning in instrument cluster, sudden loss of drive, possible short circuit.
MY 2023ā2024: Incorrectly manufactured 80A fuses in the main fuse box can fail and cause total electrical system failure. Free replacement at the dealer.
Symptoms: Sporadic electrical failures, warnings in instrument cluster, in extreme cases complete electronics failure
Software fault in the high-voltage starter-generator control unit can cause loss of drive. Affects several AMG E Performance models. Free software update at the dealer.
Symptoms: Sudden loss of drive, hybrid drivetrain warning, vehicle unable to pull away
Insulation resistance between HV circuit and vehicle earth drops below 250 kĪ© (target: >1 MĪ©). BMS locks HV relays, vehicle no longer starts. Requires OEM battery replacement.
Symptoms: Vehicle does not start, no visible fault message initially, after diagnosis: BMS lockout due to insulation fault
The electric exhaust turbocharger is powered via the 48V network. Individual cases document check engine lights. E-turbo is a unit with a 6 kW electric motor.
Symptoms: Check engine light, reduced engine power, turbo lag despite electric assist.
The 8G-DCT dual-clutch gearbox on the M139 shows occasionally erratic shift behaviour and sporadic fault messages. Rev-hanging on upshifts and rough transitions in city traffic.
Symptoms: Shifting at too-high revs, rough or delayed gear changes at low revs, occasional gearbox warning lights after spirited driving
The M139L is thermally extremely stressed (421 hp / 2.0 L). Sustained sporty use increases the risk of coolant loss and thermal management problems. Power reduction via protective programme.
Symptoms: Temperature gauge rises above normal range during spirited driving, coolant warning message, power reduction via thermal protection programme after track use
The twin-scroll turbocharger is optimised for 421 hp. With regular track use or improper cold-start behaviour it can wear prematurely. Oil supply after shutdown is critical.
Symptoms: Whistling from turbo area, power loss at high revs, blue smoke at cold start, rising oil consumption
The standard steel brakes are marginal for 2,165 kg at 500 kW system output. After repeated heavy braking performance noticeably drops off. Ceramic option available as upgrade.
Symptoms: Fading braking effect after several hard stops, brake disc discolouration, extended braking distance
Under repeated high-load stress (track use) thermal management reduces electric motor output. A design-related protection function.
Symptoms: Power reduction after several full-throttle laps, thermal management warning
The 12V battery repeatedly triggers low-voltage alarms. Door control units and comfort electronics are affected. Most frequently reported problem according to purchasing advisors.
Symptoms: Warning on display for low battery voltage, sporadic failures of door locking and comfort functions, fault memory entries
The M139L shows elevated oil consumption under high-load operation. Oil capacity 7.0 litres; nevertheless check oil level regularly between services. Increased with track use.
Symptoms: Dropping oil level between service intervals, slight oil smell on hot engine, oil level warning
Vehicle Weaknesses 11
A software fault in the engine management incorrectly detects misfires and cuts the fuel injection. Approximately 60,000 vehicles affected.
Inadequate attachment of the acoustic pad in the B-pillar. The pad can detach and impair the seat belt retractor. Belt could fail in an accident.
Acoustic pads on the B-pillar can detach and jam the seat belt retractor, preventing the pretensioner from deploying. 908 vehicles affected.
Faulty parking sensors and camera systems trigger false warnings. In snowfall, the emergency brake assist activates unintentionally.
The MBUX system freezes or becomes unresponsive. Assistance systems can be permanently deactivated. OTA updates often only temporarily relieve the symptoms.
The C254 also develops noises at the front axle when turning. Ball joints and strut top mounts wear faster with larger wheels.
MBUX system shows sporadic crashes, sluggish responses and connection drops, especially in early production months. Software updates at the workshop frequently needed.
Park assist detects non-existent obstacles, brake assist brakes without reason in snowfall, blind spot monitor fails. False alarms can trigger dangerous situations.
The MBUX system gets very hot on longer journeys. The display shows visual noise or goes black in heat. The fault disappears after cooling down.
Early C254 models show software faults: rear camera stays black, driver assistance fails, screen freezes. Usually resolvable after OTA updates.
Rattling passenger door on cobblestones, creaking centre console above 60 km/h, vibrations in the accelerator pedal. Ambient lighting elements detach.
Reports & Tests
11 owner complaints filed with NHTSA (2022ā2025). Most reported: Electrical (8), Collision Avoidance (3), Seats (2).