2021 Mercedes-Benz AMG GT Problems: 8 Known Issues

On the 2019-2025 Mercedes-Benz AMG GT M256 3.0L turbo inline-6 with EQ Boost 48V ISG, the GT 43 and GT 53 use the M256 inline-six with a 48-volt EQ Boost integrated starter-generator that replaces the conventional starter and alternator. Two distinct failures cluster here. First, a safety defect: NHTSA campaign 24V100000 covers 2021-2023 GT 43 and GT 53 whose 48-volt ground cable connection was not tightened to specification — a high-resistance ground on a 48V circuit overheats, with fire risk. Second, and far more common in owner reports, the 48V lithium battery and the ISG itself fail. Because the ISG is the starter, a failed 48V battery is not a degraded-performance condition the way a weak 12V battery is: the car simply will not crank, typically after a '48V onboard electrical system malfunction' or hybrid-battery-depleted warning. Owners on MBWorld discuss this specifically for GT 43/GT 53. This is distinct from ordinary 12V drain — it is the 48V subsystem, it is M256-specific, and it does not exist on the M177/M178 V8 GT 63 or on the C190 two-door.

On the 2019-2025 Mercedes-Benz AMG GT M256 3.0L turbo inline-6 with EQ Boost, on the X290 four-door AMG GT (GT 43 / GT 53), the transmission wiring harness can be routed incorrectly so that the electrical connector sits where it is exposed to water and road spray. The connector corrodes, and the corroded contacts can short-circuit — which Mercedes-Benz itself describes as increasing the risk of fire, and which can also strand the car with transmission fault messages. NHTSA campaign 22V533000 covered 2019-2022 GT 53 and 2021-2022 GT 43. That remedy did not hold: campaign 24V445000 was opened afterward for 2019-2025 GT 53 and 2021-2024 GT 43 because the harness connection 'might not have been correctly wired during a prior recall repair or during production' — meaning cars that already had the first recall performed can still be defective. This is a four-door X290 issue tied to the 9G-TRONIC installation and does not transfer to the C190 two-door's rear transaxle DCT.

On the 2019-2021 Mercedes-Benz AMG GT M177 4.0L twin-turbo V8, on 2019-2021 AMG GT 63 and GT 63 S four-door models (sharing the recall with the 2018-2021 E63 S), the starter motor positive cable was not installed correctly at the factory. The misposition lets the power-supply harness wires chafe against adjacent structure. Once the insulation wears through, the exposed conductor on an unfused battery-positive feed can short — Mercedes-Benz's own defect description cites both a vehicle stall (crash risk) and a fire risk. NHTSA campaign 21V217000 covers it; MBUSA's internal campaign number is 2021040013 and owner letters were mailed May 18, 2021. This is the M177 V8 four-door population; the parallel electrical fire recall on the six-cylinder GT 43/53 cars is the separate 48V ground cable campaign, and the two should not be conflated.

On the 2016-2021 Mercedes-Benz AMG GT M178 4.0L twin-turbo V8, the C190/R190 two-door AMG GT does not use a torque-converter automatic. It uses a rear-mounted Getrag/Magna 7DCL750 seven-speed dual-clutch transaxle — the same family as the Ford GT unit — and it is the single most expensive failure point on the car. Owner and specialist reports converge on a consistent set of failure modes: clutch pack wear producing shudder or hesitation on take-up, internal speed sensor failures throwing transmission control faults, oil weeping from the transaxle case weep holes, and seal/gasket leaks. Forum threads document malfunction codes tied to the electronic transmission control and DCT-specific CCP and SAP faults. The unit is intolerant of missed service: it demands strict fluid intervals and Mercedes-approved fluid, and abnormal vibration or slow engagement is the documented early warning that the gearbox is going. Because the transaxle sits at the rear of a torque tube, access is poor and labor is heavy. This is entirely distinct from the X290 four-door's front-mounted 9-speed AMG SPEEDSHIFT TCT.

On the 2016-2022 Mercedes-Benz AMG GT 4.0L V8 Biturbo M178, the C190 AMG GT mounts its rear transaxle on three ACTIVE (electronically controlled) mounts that stiffen under hard cornering and soften at idle. The most common reported failure isn't rubber breakdown — it's wiring harness or connector corrosion at the mount sensors, which trips dash warnings ("Suspension malfunction" / "Engine/transmission mount fault") and forces the mounts into a default-soft state. The fix is usually harness cleaning or connector replacement; full mount replacement is uncommon but expensive when needed (active mounts are pricey OEM parts and labor at the rear of the car is significant).

On the 2021 Mercedes-Benz AMG GT M178 LS2 4.0L twin-turbo flat-plane-crank V8, nHTSA campaign 22V042000 covers the 2021 AMG GT Black Series specifically for a front wheel speed sensor wiring harness defect, remedied by replacing the harness. The Black Series uses the M178 LS2 flat-plane-crank version of the 4.0L twin-turbo V8 (shared only with the later GT Track Series) and carries unique front-end aero and chassis hardware, and this campaign does not extend to the GT R, GT R Pro or any other C190 variant. Loss or corruption of a front wheel speed signal disables or degrades ABS, ESP and traction control simultaneously, because all three consume the same sensor data — on a 720 hp track-focused car with carbon-ceramic brakes and no stability net, that is a serious condition. The very small production volume of the Black Series means this issue is easy to miss in aggregate model-level problem data, which is exactly why it needs its own record.

On the 2021-2023 Mercedes-Benz AMG GT, the in-tank fuel pump fitted to a broad range of 2021-2024 Mercedes-Benz models including the AMG GT uses an impeller that did not meet material specification. The impeller swells or deforms in service, contacts the pump housing and binds. The mechanical resistance shuts the pump down, and the vehicle loses propulsion without warning — the car will not restart afterward. Mercedes-Benz's Part 573 report notes that before a full stall the engine may run rough and warning lamps may illuminate, which is the only advance notice an owner gets. NHTSA campaign 23V880000 covers 79,676 vehicles across GLE, GLS, C-, E-, S-, SL-, GLC-, CLS-Class, G-Class and AMG GT. Because MBUSA mailed owner letters in phases between February and December 2024, some owners were notified months after others.

On the 2016-2021 Mercedes-Benz AMG GT, the AMG GT has been recalled repeatedly across its entire production run for defects in the telematics communication module that carries the emergency call function, and the campaigns stack across different root causes rather than repeating one. NHTSA 21V058000 covers 2017-2021 AMG GT models for emergency call system software; 21V072000 covers certain 2018 AMG GT and 2020 AMG GT 53 cars whose communication module may have been deactivated during a service visit; 19V787000 covers 2016-2017 AMG GT S and 2017 AMG GT for eCall software; and 22V365000 covers 2019-2021 AMG GT models for a communication module SIM card software defect. The common consequence is that after a crash the vehicle may fail to transmit the automatic emergency call, or may transmit an incorrect vehicle location to the responder — a silent failure the owner has no way to detect, since the system gives no indication it is inoperative until it is needed. Note this is the telematics/eCall path, entirely separate from the later instrument-cluster reset recall.