2022 Mercedes-Benz C-Class Reliability Report

The core problem is losing power while driving. The accelerator stops responding, warning lights appear, and the car slows or stalls, sometimes on a freeway. Some owners report the transmission slipping into neutral on its own, a do-not-shift warning, or a seized shifter. After a 48-volt battery warning, some drivers get about 30 seconds before power drops. Other reports mention misfires, rough idle, a diesel-like engine noise, and check engine lights that dealers cannot resolve. Two complaints involve crashes, including a rear-end collision after a freeway stall.

Misfires and sudden power loss lead these reports. The check engine light comes on or flashes, the engine shakes at idle, and the car goes into limp mode or stalls at speed, sometimes without warning. Several owners say dealers found a worn valve seat or damaged cylinder head that had to be replaced, with out-of-warranty bills from $7,200 to over $10,000. These cases appear around 60,000 miles and later. Stalls and limp mode also show up in nearly new cars, including one with under 1,000 miles.

The main complaint is phantom braking. Active Brake Assist brakes hard with nothing ahead at speeds from 30 to 70 mph, nearly causing rear-end collisions. Adaptive cruise control slows abruptly, or speeds up after misreading speed limit signs. Driver aids also shut off with messages saying the sensors are dirty or the camera view is restricted. Many cases appear within the first several thousand miles, and dealers often find no fault. One report says the system neither warned nor braked before a frontal crash that totaled the car.

Blowouts and sidewall bubbles on large wheels lead these reports, often after ordinary potholes. Owners with 21 inch wheels and low-profile tires describe repeated tire and rim replacements. Other complaints cover run-flat tires that wear out quickly, uneven tread wear with a humming noise, and stored original tires showing dry cracking and tread separation with under 4,000 miles on them. Two people were injured. Several owners paid for replacement tires themselves after dealers declined to help.

These reports describe two different problems. In the first, automatic braking brings the car to a sudden full stop with no obstacle ahead, sometimes again after a software update. In the second, the brakes stick after rain, a car wash, or several days parked. The parking brake may not release without heavy throttle, and the car then lurches. A few owners report a soft pedal that sinks to the floor or a clunk felt through the pedal. One rear-end crash with an injury is blamed on brakes that did not stop the car.

Cruise control misreads speed limits. Some cars brake hard on the highway after reading a false lower limit, and others try to accelerate far above the posted speed. Other reports describe a car that will not go faster than 20 to 25 mph, or that loses power at highway speed. Two owners describe unintended acceleration while turning into a driveway or parking space. One of those ended in a crash with an injury. Dealers often find no fault or only reflash the software.

In all three reports, the air bags do not deploy in frontal or front-corner crashes. Each crash caused injuries, including head, neck, and shoulder injuries and a concussion. Four people were hurt in total. No warning lights appeared beforehand, though one owner reports intermittent electrical faults before the crash. None of the filings identifies a cause.