حساس الرادار محجوب بالأوساخ أو الثلج

Caked mud, packed snow, ice or road film over the face of a radar or ultrasonic sensor. The sensor is not broken and nothing needs replacing — it simply cannot see through what is on it, and the module correctly refuses to trust what comes back.

It is the cheapest cause in this family and the one worth eliminating first, particularly in winter, after off-road use, or on a car that has stood under trees. A wash and a careful look at the small sensor faces in the bumper is the whole repair.

The tell is weather-shaped: a system that fails in slush and returns after a wash has diagnosed itself.