Mercedes-Benz W211 Parktronic faults
Why does the W211's Parktronic beep or show red lights when there is nothing in front?
The most common cause is a single faulty sensor. The fault is found with a diagnostic tool that shows the distance of each sensor separately, and the faulty sensor's reading is clearly wrong. A wire or connector behind the bumper can also be at fault.
Why does Parktronic work poorly in winter or after washing?
Snow, ice, mud and water on the sensors cause interference, and the fault often corrects itself as they dry. However, prolonged moisture can break a sensor, and oxidised connectors are a common cause. Check the connectors before replacing sensors.
Why do the rear sensors give no signal although the front ones work?
One broken rear sensor can switch off the whole rear-end radar. First suspect the outermost sensors in the rear bumper. If replacing the sensor does not fix the fault, the wire or connector may be broken, and the fault is not visible from the outside.
Can a sensor damaged by a stone chip be painted?
The surface of the sensor can be sanded and painted, but the paint layer must not be too thick, because it hinders the radar's operation. If paint has got into the groove between the sensor and the body, the sensor should be replaced.