2017 Mercedes-Benz GLS Problems: 5 Known Issues

On the 2017-2023 Mercedes-Benz GLS, the GLS AIRMATIC system is prone to air spring leaks and compressor failure due to the vehicle's heavy curb weight (roughly 5,300-5,800 lbs). Front air springs tend to fail first. The compressor overworks to maintain ride height and eventually burns out.

On the 2017 Mercedes-Benz GLS, on the first-generation X166 GLS (early-build 2017 GLS 350d, GLS 450, GLS 550 and AMG GLS 63, produced August 2015 to June 2016; the same vehicles were sold as the GL in 2016) and its GLE sibling, the main electrical connector on the electric steering rack was not sealed properly at the factory. Water wicks through the connector into the power-steering control unit, causing a short or signal loss that abruptly deactivates power assist - typically with a red steering warning and dramatically heavier steering, sometimes preceded by clunking at parking speeds. Failures have been reported well under 25,000 miles. This is unrelated to the later X167 22V-936 steering-coupling recall and must not be confused with it.

On the 2017-2019 Mercedes-Benz GLS, the gasoline X166 GLS engines - M276 3.0 biturbo V6 (GLS 450), M278 4.7 biturbo V8 (GLS 550) and M157 5.5 biturbo V8 (AMG GLS 63) - share a well-documented failure where the seals inside the camshaft adjuster magnets (solenoids) and camshaft position sensors give up and pressurized oil is pushed into the sensor's electrical connector. From there the oil wicks along the wire strands into the main engine harness and can reach the ECU and other connectors. Early signs are oil in the cam-magnet plug and a wet valve-cover area; if ignored it produces cam-timing faults (P0016-family and P06DA-type codes), rough running and a harness or ECU replacement bill. MBWorld threads document dealers resealing solenoids under warranty and owners asking Mercedes for a campaign that was never issued.

On the 2017-2019 Mercedes-Benz GLS OM642, the 2017-2019 X166 GLS 350d uses the OM642 V6 turbodiesel, not the OM656 inline-six fitted to the X167, and it inherits the OM642's signature fault: the two seals on the engine-oil cooler that sits at the bottom of the V between the cylinder banks harden from heat and leak. Mercedes switched from orange to purple Viton seals around 2010, but owner threads document even the Viton seals failing at 7-8 years/80-120k miles. Oil pools in the valley, drips onto the transmission bellhousing and exhaust, and is frequently misdiagnosed as a rear main or turbo leak. Adjacent turbo-pedestal gaskets and the oil filter housing are common secondary leak sources on the same job.

On the 2017-2023 Mercedes-Benz GLS, the 9G-Tronic nine-speed automatic exhibits harsh low-speed shifts and hunting between gears on inclines. The transmission software struggles to select the optimal gear among nine ratios, particularly noticeable in stop-and-go traffic.