2018 Mercedes-Benz CLA Reliability Report

Shifting faults lead this category. Transmissions drop into Neutral while driving, refuse to select Reverse until the engine is restarted, or go into limp mode. Diagnoses include a failed electronic valve body at 83,000 miles, a transmission pressure control valve that failed under 1000 miles, and a faulty shifter module. Owners also report a cylinder head cover leak after 60,000 miles that soaks the starter, plus P052E codes and piston damage with smoke and power loss. In one crash the car lunged forward with the brake pressed; in another it rolled back after a shift to Neutral.

Most reports here describe a parts shortage, not a failure. Owners received a steering recall notice, then waited because dealers had no parts and no arrival date, sometimes without a loaner. Actual failures are fewer but serious. Electric power steering quits in motion or at startup with a power steering warning, and two crashes resulted, one with an injury. Dealers sometimes find nothing wrong or apply a software update. Other complaints mention clunking from the automatic steering wheel adjuster and cracking noises in curves.

Roof trim coming loose is the most common problem. The exterior panel between the windshield and panoramic sunroof lifts or flies off at highway speed, and water can leak into the cabin and damage electronics. Other reports cover a roof spoiler that keeps detaching, panoramic glass that shatters without impact, a convertible rear window coming unglued, frayed convertible top cords, a power liftgate closing on people, rear headliner fabric separating from the pillars, and front doors that swing shut on exiting passengers. One fire started in a wheel well after a tire puncture.

Two opposite failures appear: airbags that stay silent in crashes that injure occupants, and a steering wheel airbag that fires with no crash at all. Most other reports involve the airbag warning light, traced to a faulty clock spring or airbag control unit, between about 46,000 and 72,000 miles, sometimes with a dead horn or a rattle from the steering column. One owner reports a severe shin wound from a deploying knee airbag. Two complaints describe waiting on a recall repair because parts were unavailable.

Loud squealing, squeaking, and grinding are the most common complaints, often starting soon after purchase and returning after new pads. Some owners needed brakes by 9000 to 14,000 miles. In one case a rear pad wore to metal after 20K miles with no dash warning because only one rear wheel had a wear sensor. More serious reports describe unexpected emergency braking on clear roads, a pedal that did nothing for several seconds, and an injury crash where the car sped up as the driver braked.

Sudden acceleration in parking lots, with brakes that fail to stop the car, accounts for two of the three crash reports here, including one where the driver went to the hospital by ambulance. Dealers often cannot reproduce these events. Owners also describe adaptive cruise control triggering a full-force emergency stop with nothing ahead, a set cruise speed that cannot be cleared, and lane-keeping assist that bounces between lane markers. A transmission sensor fault that drops the car into Neutral at lights also appears.

Glass and trim bonding failures dominate. Rear windows loosen or detach around 50,000 to 70,000 miles, and the exterior panel between the windshield and sunroof breaks free at highway speed, becoming road debris. One sunroof exploded at 60 MPH with nothing striking it, showering the cabin with glass and causing minor injuries to 3 people. Other complaints mention wind entering through the sunroof and a side mirror that makes other cars look farther away than they are.